Self-incompatibility refers to the inability of a plant with functional pollen to set seeds when self pollinated. It is the failure of pollen from a flower to fertilize the same flower or other flowers of the same plant.
This presentation includes, Single-locus self-incompatibility- {Gametophytic self-incompatibility (GSI) and Sporophytic self-incompatibility (SSI)},2-locus gametophytic self-incompatibility, Heteromorphic self-incompatibility,Cryptic self-incompatibility (CSI) and Late-acting self-incompatibility (LSI).
Plants create their own food through the process of photosynthesis, making them autotrophs. Additionally, the process' end result is referred to as a photosynthate or photo-assimilate. In plants, the phloem is a conducting tissue that carries photosynthate (food) to every part of the plant. While storage or the point of use is referred to as the Sink, the source of production or manufacturing is referred to as the Source. The source and sink connection notion is explained in the slides. The mechanisms cover these and other crucial aspects of the topic.
Self-incompatibility refers to the inability of a plant with functional pollen to set seeds when self pollinated. It is the failure of pollen from a flower to fertilize the same flower or other flowers of the same plant.
This presentation includes, Single-locus self-incompatibility- {Gametophytic self-incompatibility (GSI) and Sporophytic self-incompatibility (SSI)},2-locus gametophytic self-incompatibility, Heteromorphic self-incompatibility,Cryptic self-incompatibility (CSI) and Late-acting self-incompatibility (LSI).
Plants create their own food through the process of photosynthesis, making them autotrophs. Additionally, the process' end result is referred to as a photosynthate or photo-assimilate. In plants, the phloem is a conducting tissue that carries photosynthate (food) to every part of the plant. While storage or the point of use is referred to as the Sink, the source of production or manufacturing is referred to as the Source. The source and sink connection notion is explained in the slides. The mechanisms cover these and other crucial aspects of the topic.
PHOTOSYNTHESIS: What we have learned so far? Zohaib HUSSAIN
No matter how complex or advanced a machine, such as the latest cellular phone, the device cannot function without energy. Living things, similar to machines, have many complex components; they too cannot do anything without energy, which is why humans and all other organisms must “eat” in some form or another. That may be common knowledge, but how many people realize that every bite of every meal ingested depends on the process of photosynthesis?
GSB uses systems biology approaches like network analysis, modeling, and omics technologies to decipher the intricate web of relationships between organisms, genes, and environmental factors within ecosystems. This holistic approach helps reveal hidden patterns and dynamics that traditional reductionist methods might miss.
May 2015 c. vulgaris to biofuel presentationJoseph Barnes
Chlorella vulgaris is a species of green microalgae capable of generating lipids suitable for conversion into biofuel via the process of transesterification. Viable production of biofuel from green microalgae requires high biomass densities, 1.0 g/L or more. We attempted to enhance cell concentrations and biomass densities of Chlorella vulgaris by growing the microalgae in a fed-batch system. A practical fed-batch system using indoor photobioreactors was designed and modified during the course of the project; commercial-grade plant fertilizers were used for the principle substrates. Additional mineral nutrients, including MgSO4, were also used in order to boost growth rates and the carrying capacity for the closed bioreactors. During the course of the experiment we implemented three different methods. The fed-batch system successfully enhanced the targeted parameters of biomass yield and cell concentration. We reached a maximum biomass density of 0.58 g/L, this was short of our goal but higher than our earlier results in previous projects. We also analyzed the effects of distinctive wavelengths of visible light (colored light versus white light) on cell concentrations. Red light (wavelength of 650 nm) led to the most positive growth, producing a value twice more than that generated using only green light (540 nm). A final variable which we briefly touched was the surface area to volume ratio of the photobioreactor.
Clocking the floral transition from phytochromes to molcular or circadian clocksSudershan Mishra
The timing of floral transition has a direct impact on reproductive success. One of the most important environmental factors that affect this transition is the change in day length (photoperiod). Classical experiments imply that plants monitor photoperiods in the leaf, and transmit that information coded within an elusive signal dubbed florigen to the apex, to reprogram development. Thus, flowering is the result of the coordination between genetic information and environmental cues. Phytochromes were considered central to this coordination in deciding the flowering time, for most part of the chronobiology research. However, intensive research in Arabidopsis over the past two decades, aided by functional genomics tools has revealed a larger role of circadian clocks in driving the flux towards flowering. Genome wide chromatin immunoprecipitation techniques have revealed that plants have evolved highly complex gene regulatory networks to modulate the timing of the floral transition. At least 306 genes and eight genetic pathways affect flowering, including the photoperiod, autonomous, vernalization, ambient temperature, and GA dependent pathways. Each pathway is centrally governed by a module of transcription factors, whose abundance in turn is regulated by daylight sensing (phytochromes) as well as generation of an internal rhythm (circadian clocks). The physiological response (flowering) occurs only when there is coincidence between the internal rhythm and phytochrome mediated abundance of the transcription factors. In case of Arabidopsis the CO-FT module is central to timing of flowering where daylight mediated CO (CONSTANS) expression leads to subsequent photoperiodic induction of the expression of FLOWERING LOCUS T (FT) gene, which might encode a major component of florigen. Similar molecular clock regulated modules have been reported in case of crops such as the Ghd7-Ehd1-Hd3a/RFT1 in case of rice and PPD1-PRR7 module in case of wheat and barley. However, whether these modules are conserved among cereal crops or they vary from one crop to another, remains to be ascertained
C4 rice - Tweaking Rice Physiology for Second green revolutionSudershan Mishra
Rice is a staple food crop for more than half of world’s population. The success of green revolution that began in 1960’s led to a tenfold increase in rice yield but it is clear now that the gains from the grains of first green revolution have exhausted. By 2050 there would be 1309 million tonnes demand of rice and C3 rice even when best managed can yield only 915 million tones. Increasing radiation use efficiency (RUE), water use efficiency (WUE) and nutrient use efficiency (NUE) are the contemporary approaches being tested on a wider scale. c.C4 type photosynthesis due to its carbon dioxide tunneling system and negligible photorespiration is much more efficient than the C3 system even at tropical temperatures where rice is generally grown. Even though engineering C4 rice requires syndromic large scale tweaking in physiology, advances in genome wide deep sequencing (popularly called as Next gen Sequencing or NSG) and genome editing platforms have brought the possibility of making C4 rice closer than ever before. A selected group of C4 genes have been inserted into rice through mutagenesis and hybridization and their effects recorded in transgenics upto 3 generations. The compartmentalized overexpression of key C4 genes using Rice DNA activation tagging constitutes another approach towards C4 rice. Because C4 plants have evolved independently multiple times from C3 origins, it is being investigated whether the key genes and gene regulatory networks that regulate C4 plants have been recruited from C3 ancestors. To facilitate this comparative transcriptomes analysis of C3 vs. C4 leaves and other C3 and C4 tissues has been done and thus the exact number of genes differentially expressing between C3 and C4 can now be calculated. High throughput OMIC data thus generated is cross referenced with whole genome databases and this has yielded sufficient number of candidate genes for bundle sheath specific expression. Fox hunting systems and Tos 17 transposable systems have also yielded a set of interesting mutants in this regard. Identification of mutants through DHPLC and TILLING are used to track down whole genome duplication events in the evolution towards C4 rice. While the discovery of cis acting sequences in C3 to C4 transition is a favorable advance, our further studies are limited by the poor resolution of transcript profiles and epigenetic signatures. Availability of only a few models of in silico studies about performance of C4 rice under dense crop canopies is another limitation.
AUXIN a morphogen in plant growth and developmentSudershan Mishra
the presentation encompasses auxin synthesis, conjugation, degradation, polar and lateral transport and signalling and how all of these together have a bearing on programming and design of the whole plan
Everything about photoperiodism from scratch to smart, from the oldest models to the latest models as well as proposed one, exclusive and elusive illustrations and models for proper understanding
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
Nutraceutical market, scope and growth: Herbal drug technologyLokesh Patil
As consumer awareness of health and wellness rises, the nutraceutical market—which includes goods like functional meals, drinks, and dietary supplements that provide health advantages beyond basic nutrition—is growing significantly. As healthcare expenses rise, the population ages, and people want natural and preventative health solutions more and more, this industry is increasing quickly. Further driving market expansion are product formulation innovations and the use of cutting-edge technology for customized nutrition. With its worldwide reach, the nutraceutical industry is expected to keep growing and provide significant chances for research and investment in a number of categories, including vitamins, minerals, probiotics, and herbal supplements.
2. What are we going to talk about?
• The most important aspect of our survival; which is why it
happens to be a global concern- “FOOD”
• The process that is at the heart of careers and lives of all of us
sitting in the room in particular and the world in general-
“PHOTOSYNTHESIS”
• The protein which happens to be the most abundant protein
on earth, singularly responsible for entry of more than 99% of
inorganic carbon in the living system – “RUBISCO”
2
3. Overview
• Scale of yield enhancement required
• Theoretical framework for analyzing yield
• Is there scope for yield enhancement?
• Can improvement in photosynthesis help?
• Potential RUE of crops
• Opportunities for Hacking Photosynthesis
• Enabling technologies
• Brief discussion about each of the opportunities including the
latest research idea
• In-depth discussion about the photorespiratory bypass
• Conclusion
• Future perspectives
3
4. Scale of yield enhancement required to
realize global food security
Current Levels Future (2050) Levels Options at hand
Population stands at 7.7
Billion
Population will be 9.4
Billion
• Increase the land area
under agriculture
• Find alternate sources
of food
• Increase the
proportion of light
energy harvested by
crops
• Increase the harvest
index
• Increase the
photosynthetic
efficiency
Current production level
has stagnated after rapid
increase in 1960s and is
increasing annually at a
rate of 1.2 percent; this
rate is decreasing every
year
2.2 percent increase in
yield is required annually
i.e. 83 to 91% yield
enhancement is required
Overall agricultural
resources are shrinking
by 0.95% annually
22-28% decrease in
agricultural resources
compared to current
levels would have
occurred by 2050
Walker et.al., 2016
4
5. Theoretical framework for analyzing yield
increase
• Yp = η·Pn; Pn = St·εi·εc/k
• Yp = Yield potential
• η = harvest index/ efficiency with which biomass is
partitioned into harvestable product
• Pn = primary productivity
• St = Annual integral of incident solar radiation (MJ m-2)
• εi = efficiency with which radiation is intercepted by the crop
• εc = efficiency with which intercepted radiation is converted
into biomass
• k = energy content of plant mass 5
Long et.al., 2018
6. Theoretical framework for analyzing yield
increase Contd..
• Yp is therefore determined by the combined product of
three efficiencies, each describing broad physiological
and architectural properties of the crop
• εi
• εc
• η
• εi is determined by the speed of canopy development
and closure, canopy longevity, size and architecture.
• εc is determined by the combined photosynthetic rate of
all leaves within the canopy, less crop respiratory losses.
6
Long et.al., 2018
7. Is there any scope for yield enhancement?
• Over the past 50 years, increase in Yp has been successfully achieved
largely through increase in η. Grain in the modern cultivars of
cereals can represent 60% of the total above-ground biomass at
harvest. While some opportunities for further increase in η remain,
it seems unlikely that a η much greater than 0.6 may be realized
• Increased Yp also results from increased εi through earlier canopy
development and ground cover, and selection of cultivars able to
respond to additional nitrogen fertilization without lodging. With
these cultivars achieving an εi of 0.9 over the growing season,
again, scope for further improvement is very limited
• Further increase in Yp can only be achieved by an increase in εc
which is determined by the efficiency of photosynthesis corrected
for respiratory losses, summarily called as Radiation Use Efficiency
(RUE) 7
Long et.al., 2018
8. Will improvement in photosynthesis help?
The arguments against
• There is lack of correlation
between crop yield and
photosynthetic rates (Evans &
Dunstone, 1970)
• Photosynthesis is limited by
sink capacity (Borras et al. ,
2004)
Supporting Facts
• European Stress Physiology and
Climate Experiment (ESPACE)
project grew a single genotype of
spring wheat under FACE 650
µmol mol−1) at 7 sites in Germany,
Ireland, the UK, Belgium and the
Netherlands, over 3 consecutive
growing seasons
• Across these sites, photosynthesis
of the flag leaf the major source of
assimilate for the grain – was on
average increased by 50%, and
grain yield was increased by 35%
8
Long et.al., 2018
9. What is the potential RUE (εc ) of crops
Table 1 - Efficiency of the transduction of intercepted solar radiation into plant carbohydrate
through photosynthesis of crop leaf canopies
9
Long et.al., 2018
Observed maxima- 0.034 (C3) and 0.042 (C4)
i.e. only 70% of the theoretical
10. Opportunities for hacking photosynthesis
Major Issue Strategy Approach
Theoretical
Increase
Light
Saturation
of leaves
Can be improved by a
canopy architecture that
provides better distribution
of light by maintaining the
maximum efficiency of
photosynthesis under light-
limiting conditions and by
increasing photosynthetic
rate at light saturation
Modifying canopy
architecture
0.051
Improved regeneration of
acceptor molecule
Improving RUBISCOs for
higher rates of catalysis of
carboxylation
Relaxing Photoprotection
Photo-
respiration
Bypassing Photorespiration
Improving RUBISCO to be
specific for carboxylation
0.060
Converting C3 plants to C4
Algal Mechanisms
0.073
Photorespiratory Bypass
Table 2 – Specific opportunities for increasing photosynthesis
10
Long et.al., 2018
11. Enabling Technologies
Technology/Tools Applications
Bacterial transformation Engineering photosynthesis in cyanobacteria
Nuclear transformation
Engineering of nucleus-encoded components of the
photosynthetic apparatus; expression of novel genes and
pathways. Development of synthetic chromosomes.
Plastid transformation
Engineering of plastid-encoded components of the
photosynthetic apparatus; expression of novel genes and
pathways of carbon metabolism.
Mitochondrial
transformation
Engineering of mitochondrially encoded components of
the respiratory chain to minimize respiratory losses;
expression of novel pathways of carbon metabolism.
Multigene engineering
Engineering of protein complexes in the electron
transfer chain; engineering of carbon fixation pathways.
11
ort et.al., 2018
Table 3 – Specific molecular biology and systemic techniques for hacking photosynthesis
12. Enabling Technologies
Technology/Tools Applications
Protein design
Redesign of the electron transfer chain; Rubisco
engineering; redesign of carbon-fixing enzymes.
Synthetic genomics
Radical redesign of the photosynthetic apparatus via
synthetic plastid genomes and/or artificial
(mini)chromosomes in the nucleus.
Design of logic circuits;
development of sensors for light
intensity, light quality,
temperature, and CO2
concentration
Smart canopy concept.
Phenotyping in the field
Evaluation of design concepts under field conditions
and further optimization through mutagenesis.
12
ort et.al., 2018
13. Modifying crop canopies to increase εc
• Leaf photosynthesis responds non-linearly to increases in solar
energy
• A mature crop may have 3 or more layers of leaves (i.e. a leaf
area index of ≥ 3). If the leaves are roughly horizontal, the
uppermost layer would intercept most of the light at midday,
while about 10% may penetrate to the next layer and 1% to
the layer below that
• PPFD intercepted per unit leaf area by an almost horizontal
leaf at the top of a plant canopy would be 1400 µmol m−2 s−1
i.e. about 3 times the amount required to saturate
photosynthesis .
• 2/3rd of the energy intercepted by the upper leaves is wasted
• Upper layers must intercept less light making way for the
lower layers
13
Andrew et.al., 2018
14. Modifying crop canopies to increase εc
• Upper leaves should be vertical while lower leaves should be
horizontal . A leaf with a 75° angle with the horizontal
intercepts 700 µmol m−2 s−1, just sufficient to saturate
photosynthesis
• Remaining direct light (1300 µmol m−2 s−1) penetrates to the
lower layers of the canopy.
• This distribution almost doubles the efficiency of such as
canopy as compare to a canopy with horizontal leaves
• Although this is only about half the increase that would occur
if the sun remained directly over-head , it nevertheless
suggests considerable improvement may still be achieved by
manipulation of canopy architecture
14
Andrew et.al., 2018
15. Research Insight/Case Study
Chlorophyll Can Be Reduced in Crop
Canopies with Little Penalty to
Photosynthesis
Berkley J. Walker, Darren T. Drewry, Rebecca A. Slattery, Andy VanLoocke, Young
B. Cho, Donald R. Ort
Journal- Plant Physiology
Published February 2018.
DOI: https://doi.org/10.1104/pp.17.01401
15
16. Concise review-
• Hypothesis- Reducing Chl content in upper leaves and
promoting it in lower leaves could increase canopy
photosynthesis
• Methodology- Relationship among leaf Chl, optical properties
and photosynthetic capacity was measured in 67 different
soybean varieties and integrated into a biophysical model
(WIMOVAC) of canopy-scale photosynthesis to simulate the
intercanopy light environment and carbon assimilation
capacity of canopies with varying chl content, as well as
among wild types and chl deficient mutants
• One line Summary- An empirically parameterized model of
canopy photosynthesis in soybeans reveals that leaf
chlorophyll can be reduced in upper leaves with significant
nitrogen savings and only minor reductions in daily carbon
gain.
16
Walker et.al., 2018
17. Modifying crop canopies to increase εc
Figure 1 – Variation in canopy photosynthesis with canopy architecture, A- Light interception as
affected by two type of architecture X & Y, B- Accumulative LAI vs PPFD for X and Y, C- PPFD vs CO2
assimilation rate for X & Y, D- comparison of Diurnal PPFD and Photosynthetic rate for X & Y.
17
Walker et.al., 2018
18. Smart Canopy Concept-
1. Transitioning from vertical leaves in high light in the upper
canopy to horizontal leaves in low light deeper in the canopy
2. Deploying a Rubisco with a high catalytic rate in the upper
leaves, (even at the expense of specificity for CO2 over O2), &
replacing Rubisco with a high specificity form in the lower
canopy where light is limiting to minimize photorespiration
3.In upper leaves small antennas in large numbers, in lower
leaves larger antenna systems maybe fewer in number
4. Repositioning floral organs and panicles inside the canopy
5. Decreasing leaf chlorophyll content in sun-exposed leaves
6. Engineering of a switchable system where a leaf in a nascent
canopy initially operates a light-driven CO2-concentrating
mechanism and later conducts C3 photosynthesis after it is
shaded during canopy development 18
Walker et.al., 2018
19. Triple penalty of RUBISCO-
• Penalty 1- Catalyses oxygenation of RuBP leading to
photorespiration which translated into loss of fixed carbon by
about 25 to 40 %
• Penalty 2- maximum catalytic rate of Rubisco (kc
cat) is
remarkably slow compared with most plant enzymes, such
that large amounts of the protein are required to achieve the
photosynthetic rates necessary to support high productivities
in C3 crops. It is already 50% of total leaf protein hence
increasing it is not an option on v/v basis
• Penalty 3- The forms with higher CO2 specificity (τ) over O2
have very poor catalytic rates (kc
cat).
19
Andrew et.al., 2018
20. Improving catalysis and/or specificity of
RUBISCO
• Increased τ will result in increased leaf and canopy
photosynthesis If
1. A fixed inverse relationship between kc
cat and τ implied
from measurements is assumed,
2. Increasing concentration of Rubisco per unit leaf area
is not an option
20
Andrew et.al., 2018
21. Engineering chloroplasts to improve Rubisco
catalysis: prospects for translating
improvements into food and fiber crops
Robert E. Sharwood
Journal- New Phytologist
New Phytologist (2018) 213: 494–510
doi: 10.1111/nph.14351
21
Research Insight/Case Study
22. Concise review-
• Hypothesis- Using plastid transformation for bioengineering of
improved forms of RUBISCO in terms of specificity and/or
catalysis can enhance photosynthetic efficiency
• Methodology- Saturation state kinetics of RUBISCO from
varied sources like Bacteria, Cyanobacteria, Red algae, Diatom
C3 and C4 plants was studied to delineate the specificity and
carboxylation properties and candidate RUBISCO was
modelled using biophysical simulative transformation models
• One line Summary- The model generates much evidence in
favor of a strong negative correlation between specificity and
carboxylation in case of RUBISCO. The study suggested that
ideally, a crop should express a high kc
cat RUBISCO in the upper
canopy leaves exposed to full sunlight and a high τ RUBISCO
in the shaded lower canopy leaves 22
Sharwood, 2018
23. Exploring natural diversity of RUBISCO
23
Sharwood, 2018
Fig 2a - Natural diversity of Rubisco catalysis exists among photosynthetic organisms as shown in the
relationships between (a) Kc (Michaelis constant for CO2), (b) specificity for CO2 opposed to O2 (Sc/o) and
the carboxylation speed (kcat
c). Solid lines represent the exponential relationship y = 4.9e0.377x r2 = 0.5 and
y = 134.5e 0.137x r2 = 0.4
24. Exploring natural diversity of RUBISCO
24
Sharwood, 2018
Fig 2b – (C)Modelling at 25°C of the influence of rice (C3 monocot), tobacco (C3), Griffithsia monilis (red
alga) and maize (C4 monocot) Rubisco catalytic parameters on CO2 assimilation for C3 photosynthesis in
response to chloroplastic CO2 partial pressures (CC) under Rubisco activity limiting and under electron
transport limiting conditions. (d) Comparing the influence of rice, tobacco, G. monilis, Synechococcus
PCC6301, Rhodospirillum rubrum, Cyanobium spp. PCC7001 and maize Rubisco catalysis in CO2 conditions
experienced by plants operating a Kranz-type C4 photosynthetic pathway under Rubisco activity limiting
conditions
25. Significant Findings
• Following the steady-state biochemical model of leaf
photosynthesis, the C3 photosynthetic CO2 uptake rate (A) is
either limited by the maximum Rubisco activity (Vc,max) or by
the rate of regeneration of RuBP which is determined by the
rate of whole chain electron transport (J).
• If J is limiting, increase in τ would increase net CO2 uptake
because products of the electron transport chain would be
partitioned away from photorespiration into photosynthesis
• If Rubisco from the non-green algae Griffithsia monilis can be
expressed in place of the present C3 crop RUBISCO, then
canopy carbon gain can be increased by 27%.
25
Sharwood, 2018
26. Significant Findings
Note-
The final row represents simulation of the gain that can be achieved if a form of Rubisco with a high kc
cat (A.
edulis) can be expressed in the sunlit leaves and if a form with high τ (current C3 average) can be expressed in the
shade leaves.
kc
c, maximum catalytic rate of Rubisco; τ , specificity of Rubisco for CO2 relative to O2; Asat, maximum rate of
photosynthesis; Rubisco, ribulose 15-biphosphate carboxylase/oxygenase.
26
Sharwood, 2018
Table 4 - Reported values for kc
cat and AC’ of species under study
27. Improved regeneration of Acceptor Molecule
• The progenitors of modern crop plants evolved in, and are thus
adapted to, an atmospheric [CO2] of about 240 ppm.
• The accelerated rate of Rubisco-catalyzed carboxylation at today’s
[CO2] of >400 ppm has led to a kinetic limitation in the
regeneration of the CO2 acceptor molecule ribulose-1,5-
bisphosphate (RuBP), which will become increasingly limiting as
[CO2] increases further
• If the rate of carboxylation at Rubisco is increased, then Jmax
should also be increased to gain maximum benefit From kinetic
data, it may be calculated that as a result, Jmax/Vc,max would need
to increase by 30% to maintain an optimal distribution of
resources 27
Andrew et.al., 2018
28. Identifying the key limiting points
• Unlike Vc,max, regeneration of RuBP does not depend on the
amount or the properties of any single protein, but on the
complete photosynthetic electron transport chain and on all the
enzymes of the Calvin cycle except Rubisco
• Transgenic plants with small decreases in the quantities of specific
proteins produced by antisense technology in tobacco suggest
that two points in this chain limit Jmax and strongly control the rate
of RuBP synthesis
• 1. The cytochrome b6/f complex in the electron transport chain
• 2. Sedoheptulose-1:7-bisphosphatase (SbPase) in the Calvin cycle
28
Andrew et.al., 2018
29. Research Insight/Case Study
Simultaneous stimulation of sedoheptulose 1,7-
bisphosphatase, fructose 1,6 bisphophate aldolase
and the photorespiratory glycine decarboxylase-H
protein increases CO2 assimilation, vegetative
biomass and seed yield in Arabidopsis
Andrew J. Simkin1, Patricia E. Lopez-Calcagno1, Philip A. Davey1, Lauren
R. Headland1, Tracy Lawson1, Stefan Timm2, Hermann Bauwe2 and
Christine A. Raines1*
Journal- Plant Biotechnology Journal
Plant Biotechnology Journal (2017) 15, pp. 805–816
doi: 10.1111/pbi.12676
29
Simkin et.al., 2017
30. Concise review-
• Hypothesis- To explore the possibility that the simultaneous
increase in the activity of enzymes of both the CB cycle and the
photo respiratory pathway could lead to a cumulative positive
impact on photosynthetic carbon assimilation and yield
• Methodology- SBPase, FBPA and GDC-H either alone or in
combination were over expressed in Arabidopsis plants using
tissue specific promoters and T3 plants were analyzed for
chlorophyll fluorescence, photosynthetic efficiency, carbon
assimilation and overall growth and yield
• One line Summary- Simultaneous over expression of CB cycle
enzymes along with PR pathway enzymes lead to an enhancement
in dry weight by 39 to 45%
30
Simkin et.al., 2017
31. Increased photosynthetic efficiency in
young over expressing seedlings
Fig 3 -Photosynthetic capacity and
leaf area in transgenic seedlings
determined using chlorophyll
fluorescence imaging. (a,b)- Fq’/Fm’
(maximum PSII operating efficiency)
values of the whole plant at 200
lmol/m2/s and (c)- leaf area at time
of analysis. Azygous controls (A)
recovered from a segregating
population. Lines over-expressing
SBPase (S), FBPA (F), GDC-H protein
(H), SBPase and FBPA (SF) and
SBPase, FBPA and GDC-H (SFH) are
represented. Significant differences
between lines(P < 0.05) are
represented as capital letters
indicating whether each specific line
is significantly different from another
(i.e. SBPase lines (S) are significantly
bigger than wild type (WT) and
azygous lines (A)). Numbers indicate
% increases over WT.
31
Simkin et.al., 2017
32. Enhanced Photosynthetic CO2 fixation rates
Fig- 4 Photosynthesis
carbon fixation rates
determined as a
function of light
intensity in developing
leaves. Red arrow
indicates optimum
growth light intensity.
Lines over-expressing
SBPase (S), FBPA (F),
GDC-H protein (H),
SBPase and FBPA (SF),
and SBPase, FBPA and
GDC-H (SFH) are
represented. Results are
based on 4 to 7 plants
per line
32
Simkin et.al., 2017
33. Growth analysis
Fig 5- Growth analysis of the transgenic and control plants after 38 days. Lines over-expressing
a single transgene, SBPase (S), FBPA (F), GDC-H protein(H), two transgenes, SBPase and FBPA
(SF), or three transgenes, SBPase, FBPA and GDC-H (SFH) are shown.
33
Simkin et.al., 2017
34. Growth analysis Contd..
Fig 6a Growth analysis of C and transgenic lines grown in low light (a) Leaf area per plant evaluated over the
first 38 days. (b) Final dry weight (g) after 38 days of development and statistical differences between lines.
% increases over C are indicated within the columns. Lines over-expressing SBPase (S), FBPA (F), GDC-H
protein (H), SBPase and FBPA (SF) and SBPase, FBPA and GDC-H (SFH) are represented. Significant
differences between lines (P < 0.03) are represented as capital letters indicating whether each specific line is
significantly different from another.
34
Simkin et.al., 2017
a b
35. 35Fig 6b- GDC-H and GDC-H with SBPase and FBPA overexpression in Arabidopsis
differentially impact biomass and seed yield. (a, c) Dry weight and (b, d) seed weight
were determined at seed harvest.
36. Relaxing Photoprotection
• When light intensity is too high or increases too fast for photo
chemistry to use the absorbed energy, many photoprotective
mechanisms are induced to protect the photosynthetic
antenna complexes from photo-oxidation
• Excess excitation energy in the photosystem II (PSII) antenna
complex can be harmlessly dissipated as heat, which is
observable as a process named non-photochemical quenching
of chlorophyll fluorescence (NPQ). The rate of NPQ relaxation
is slower than the rate of induction
• This slow rate of recovery of PSII antennae from the quenched
to the unquenched state implies that the photosynthetic
quantum yield of CO2 fixation is transiently depressed by NPQ
upon a transition from high to low light intensity 36
Andrew et.al., 2018
37. Basics of NPQ
Fig 8- The highly quenched state of photosystem II is associated with zeaxanthin, the
unquenched state with violaxanthin. Enzymes interconvert these two carotenoids, with
antheraxanthin as the intermediate, in response to changing conditions, especially changes in
light intensity. Zeaxanthin formation uses ascorbate as a cofactor, and violaxanthin formation
requires NADPH
37
Plant Physiology, Taiz and Zeiger, 3rd 3d.
38. Basics of NPQ
Fig- 7- Nonphotochemical quenching regulates light harvesting by PSII. In limiting light, LHC proteins
efficiently transfer excitation energy to the reaction center of PSII. In excess light, when the rate of
photosynthesis is saturated and protons accumulate to a high concentration in the thylakoid lumen, a
flexible type of nonradiative dissipation is induced in the PSII antenna on a timescale of seconds to
minutes. Proton binding to the PSBS protein and accumulation of zeaxanthin (not shown) causes a
conformational change or reorganization of PSII that switches the antenna into a dissipative state that
prevents overexcitation of chlorophyll and overreduction of the electron transport chain.
38
Biochemistry and Molecular Biology of Plants, Buchannan et al. 2nd ed., 2015
39. The Problem
Fig 8- Photoprotection and CO2 fixation during sun-shade transitions. When leaves are exposed to high light, the
rate of CO2 fixation is high, and excessive excitation energy is harmlessly dissipated through NPQ. NPQ is
correlated with the abundance of PsbS and further stimulated by the de-epoxidation of violaxanthin to
zeaxanthin, catalyzed by VDE. Upon transition to low light, CO2 fixation becomes limited by the reduced form of
NADP and ATP derived from photosynthetic electron transport, which in turn is limited by high levels of NPQ. The
rate of CO2 fixation therefore remains depressed until relaxation of NPQ is complete. This can take minutes to
hours and is correlated with the rate of zeaxanthin epoxidation, catalyzed by ZEP.
39
Andrew et.al., 2018
40. Research Insight/Case Study
Improving photosynthesis and crop productivity by
accelerating recovery from photoprotection
Johannes Kromdijk,1* Katarzyna Głowacka,1,2* Lauriebeth Leonelli,3
Stéphane T. Gabilly,3 Masakazu Iwai,3,4 Krishna K. Niyogi,3,4† Stephen
P. Long1,5†
Journal- Science
18 Nov 2016:
Vol. 354, Issue 6314, pp. 857-861
DOI: 10.1126/science.aai8878
40
41. Concise review-
• Hypothesis- By accelerating the xanthophyll cycle
intermediates and increasing PsbS, NPQ would decline more
rapidly on transfer of leaves to shade
• Methodology- Nicotiana tabacum was transformed with the
coding sequences of Arabidopsis VDE, ZEP, and PsbS under the
control of different promoters for expression in leaves.
Suitable traansformants were testes for faster relaxation of
NPQ and recovery of CO2 fixation rate
• One line Summary- Transgenic expression of Arabidopsis VDE,
PsbS, and ZEP (VPZ) in combination in tobacco led to a marked
and statistically significant acceleration of NPQ relaxation on
transfer of leaves from high light to shade. This led to a more
rapid recovery of the efficiency of photosynthetic CO2
assimilation in the shade.
41
Kromdijk et.al., 2016
42. Faster relaxation of NPQ and recovery of
CO2 fixation rate
Fig 9- Transient adjustment of NPQ and net CO2 assimilation. (A) Dark relaxation of NPQ after exposure to
alternating high and low light in young seedlings of wild-type N. tabacum (WT) and three lines expressing AtVDE,
AtPsbS, and AtZEP (VPZ). (B) Time course of net CO2 fixation rate in fully expanded leaves in response to a
decrease in light intensity of 2000 to 200 mmol photons m−2 s−1 at time zero, indicated by the black arrow.
42
Kromdijk et.al., 2016
43. Effects of fluctuating light on the efficiency of
photosynthetic CO2 assimilation
Fig 10- Photosynthetic efficiency and
NPQ under steady-state and
fluctuating light. (A) Quantum
efficiency of leaf net CO2 assimilation
(FCO2max) under steady-state light. (B)
FCO2max under fluc-tuating light. (C)
Quantum efficiency of linear elec-
tron transport (FPSIImax) under
steady-state light. (D) Quantum
efficiency of linear electron transport
(FPSIImax) under fluctuating light. (E)
Average NPQ corresponding to (A)
and (C). (F) Average NPQ
corresponding to (B) and (D
43
Kromdijk et.al., 2016
44. Productivity under field conditions
Fig 11- Productivity of field-grown N. tabacum plants. Lines expressing AtVDE, AtPsbS, and AtZEP
(VPZ) produced 15% larger plants than did the WT. (A) Total dry weight. (B) Leaf area. (C) Plant
height. Data were normalized to WT. Error bars indicate SEM (n = 12 blocks), and asterisks indicate
significant differences between VPZ lines and WT (a = 0.05).
44
Kromdijk et.al., 2016
45. Abundance of Xanthophyll Cycle
Intermediates
45
Kromdijk et.al., 2016
Table 5- Xanthophyll cycle pigment concentrations and De-epoxidation state
46. Incorporating Algal CCM Mechanisms
Fig 12- Cyanobacterial CCM components for improved photosynthesis Carboxysomes of Cyanobium PCC7001,
used in this study, consist of many thousands of polypeptides, arranged in an icosahedral structure. In this model,
a single layer of shell-bound Rubisco (CbbLS, green) is shown, with carboxysomal CA (orange). CsoS2
(yellow/brown) interlinks Rubisco and the shell made predominantly of CsoS1A hexamers (light blue). These and
ancillary shell proteins (CsoS1D and CsoS1E, dark blue) enable substrate transport via central pores. Pentameric
vertex proteins (CsoS4AB, purple) complete the structure
46
Long et.al., 2018
47. Research Insight/Case Study
Carboxysome encapsulation of the CO2-fixing
enzyme Rubisco in tobacco chloroplasts
Benedict M. Long 1, Wei Yih Hee 1, Robert E. Sharwood2, Benjamin
D. Rae 2, Sarah Kaines 1, Yi-Leen Lim 1, Nghiem D. Nguyen 2, Baxter
Massey 1, Soumi Bala2, Susanne von Caemmerer
Journal- Nature Communications
September 2018
Nature Communications volume 9,
Article number: 3570 (2018)
47
48. Concise review-
• Hypothesis- Targeted chloroplastic expression of Cyanobium
carbozysomes assembly proteins may lead to carboxysome
assembly in tobacco chloroplasts. The latter shall result in
enhanced photosynthetic efficiency and growth
• Methodology- Nicotiana tabacum was transformed with genes for
2 carboxysome assembly proteins CsoS1A and CsoS2
singularly(CyLS) and in combination (CyLS-s1s2). The assembled
structure was isolated and parametrically compared with
cyanobium carboxysomes using TEM and immunogold
localization. The transformants were screened for growth
parameters
• One line Summary- A structure empirically similar to
carboxysomes was assembled and it could be clearly visualized
within the chloroplast. However the native functionality was not
observed.
48
Long et.al., 2018
49. Carboxysome assembly and visualization
a
Fig 13a- Carboxysomes are synthesized in tobacco chloroplasts from four proteins. (a) a model (b)TEM of
chloroplasts from tobacco expressing Cyanobium Rubisco (CyLS plants) and (c) tobacco expressing Cyanobium
Rubisco along with the shell proteins CsoS1A and CsoS2 (CyLS-S1S2 plants), The inset in c at higher magnification
(d). Negatively stained carboxysomes purified from CyLS-S1S2 plants (e) and carboxysomes purified from
Cyanobium cyanobacterial cells (f).
49
Long et.al., 2018
50. Carboxysome assembly and visualization
50
Long et.al., 2018
Fig 13b (g) Diameters of carboxysomes from wild-type Cyanobium cells (cyan line) and carboxysomes purified
from CyLS-S1S2 plants (magenta line) determined using a Nanosight particle analyser. (h) TEM of ultrathin sections
through CyLS-S1S2 plant chloroplasts reveal the presence of elongated structures (arrowheads) associated with
the more regular carboxysome structures. These elongated structures co-purify with the plant-expressed
carboxysomes.
h
51. Plant Growth Analysis
Fig. 14 Form-1A Rubisco-dependent
plant growth. CO2 assimilation rates
of wild-type and transgenic tobacco
expressing Cyanobium PCC7001
Form-1A Rubisco (CyLS) and
expressing Cyanobium Rubisco
together with the carboxysome
genes csoS1A and csoS2 (CyLS-S1S2),
determined by gas exchange of
attached leaves. Rates are expressed
on a leaf area basis (a) with an
expanded scale for the same data
presented in b to show assimilation
rates in transformed plants. Fitted
lines (WT, black; CyLS, cyan; CyLS-
S1S2, yellow)
(C) CO2 assimilation rates of leaf discs
from each plant line from plants
grown at 2% (v/v) CO2 in membrane
inlet mass spectrometer (MIMS)
assays. Solid lines (WT, magenta;
CyLS, cyan; CyLS-S1S2, yellow) The
dashed lines for CyLS and CyLS-S1S2
are modelled assimilation rates using
the same parameters as a, b. (d)
Growth measured as plant height
post
51
52. Plant Growth Analysis
Fig 15- Growth phenotypes at days after germination (e–g) and at maturity (h–j) of wild-type (e, h), CyLS
(f, i) and CyLS-S1S2 (g, j) plants grown in soil at 2% (v/v) CO2 in 20 cm pots. Note the delayed germination
and time to reach maturity in both transformant lines
52
Long et.al., 2018
53. Loss due to photorespiration
Fig 16- Calculated actual and potential rates of crop canopy photosynthesis versus temperature, where potential
is defined as the rate in the absence of photorespiration. The difference represents the loss caused by
photorespiration. Calculation assumes a crop with a leaf area index of 3 and a photon flux above the canopy of
1800 µmol m−2 s−1 (i.e. full sunlight)
53
Walker et.al., 2016
54. Is photorespiration actually required?
• Photorespiration can dissipate excess excitation energy at high PPFD, involves the
synthesis of serine and glutamate, and transfers reductive power from the
chloroplast to the mitochondrion. This has led some to suggest that
photorespiration is essential for normal plant function
• However, xanthophylls provide a far more effective means of dissipating excess
energy. Unlike photorespiration, this dissipation mechanism is not a significant drain
on the ATP and NADPH produced by the light reactions. Further, dissipation of
energy as heat through xanthophylls is reversible.
• In addition, the photosynthetic cell has pathways besides photorespiration for
amino acid synthesis and transfer of reductive energy to the cytosol Hence the
supposed ‘beneficial’ functions of photorespiration are redundant within the cell.
• Further, photorespiration can be eliminated without detriment to the plant by
growing plants in a very high concentration of CO2, a competitive inhibitor of the
oxygenase activity of Rubisco. For example, wheat can grow normally and can
complete its life cycle under these unusual conditions. Commercial growers of some
greenhouse crops increase [CO2] to three or four times the normal atmospheric
concentration
54
Walker et.al., 2016
55. Research Insight/Case Study
Synthetic glycolate metabolism pathways stimulate
crop growth and productivity in the field
Paul F. South, Amanda P. Cavanagh, Helen W. Liu, Donald R. Ort*
Journal- Science
Feb 2019
Vol. 363, Issue 6422, eaat9077
DOI: 10.1126/science.aat9077
55
56. Concise review-
• Hypothesis- Installing a non native, synthetic glycolate metabolism
pathway in tobacco stimulate crop growth and productivity in the field
• Methodology- Nicotiana tabacum cv. Petite Havana was transformed
with three different photorespiratory alternative pathway (AP) designs
using multigene constructs assembled by Golden Gate cloning . Native
photorespiratory pathway was suppressed using a long hairpin RNA
interference (RNAi) construct. The transformants were analyzed for
resistance to photorespiratory stress and greater biomass accumulation
as a result of Photorespiratory bypass.
• One line Summary- AP3 plants show increased photosynthetic rates,
quantum efficiency, and biomass accumulation in replicated field trials
particularly due to have an altered photorespiratory metabolite profile
that forced a greater flux of glycolate through the synthetic pathway 56
South et.al., 2019
57. The Three SyntheticAlternate Pathways
Fig 17- Model of three alternative photorespiration pathway designs. AP1 (red) converts glycolate to glycerate
using five genes from the E. coli glycolate pathway encoding the enzymes glycolate dehydrogenase, glyoxylate
decarboxylase, and tartronic semi- aldehyde reductase. AP2 (dark blue) requires three introduced genes
encoding glycolate oxidase, malate synthase, and catalase (to remove hydrogen peroxide generated by glycolate
oxidase). AP3 (blue) relies on two introduced genes: Chlamydomonas reinhardtii glycolate dehydrogenase and
Cucurbita maxima malate synthase.
57
South et.al., 2019
58. Gene and protein analysis confirm
chloroplast-localized transgene expression
Fig 18- A. qRT-PCR analysis of the two transgenes in AP3 and the target gene PLGG1 of the RNAi construct.
Results for three independent transformation events are shown with (1, 5, and 8) and without (8, 9, and 10)
PLGG1 RNAi. (B) Immunoblot analysis from whole leaves and isolated chloroplasts, including the insoluble
membrane fraction, using custom antibodies raised against the indicated target genes, cytosolic marker actin,
and chloroplast-specific marker platoglobulin 35 (PGL35). Five micrograms of protein was loaded per lane. Arrows
indicate detected protein based on molecular weight.
58
A B
South et.al., 2019
59. AP plants are resistant to photorespiration
stress
Fig. 19- AP plant lines are more photoprotective under photo-respiration stress. (A) Representative photos of 9-
day-old T2 transgenic tobacco lines during the chlorophyll fluorescence photoprotection screen for AP pathway
function showing AP3 protecting photosystem II from photodamage under severe photorespiratory conditions.
(B) Combined values of the three AP construct designs with and without RNAi targeting the glycolate-glycerate
transporter PLGG1.
59
South et.al., 2019
60. AP plants show enhanced biomass
accumulation in greenhouse growth studies
Fig 20- Photorespiration
AP lines increase biomass
under greenhouse
conditions. (A) Photos of
6-week-old AP3 and WT
plants grown in the
greenhouse. Individual
plant lines are indicated
in the labels below the
plant. (B) Percent
difference in total dry
weight biomass of the
indicated combined plant
lines.
60
South et.al., 2019
61. AP3 plants have an altered
photorespiratory metabolite profile
Fig 21-
Photorespiratory and
AP3 metabolic
intermediates. (A to
F) Relative amount of
the indicated
metabolite detected
from ~40 mg of leaf
tissue (fresh weight;
FW) sampled in the
late morning.
Metabolite
concentrations were
reported as
concentrations
relative to the
internal standard
61
South et.al., 2019
62. AP3 plants exhibit increased
photosynthetic rate and chloroplast [CO2]
Fig 22- Photosynthetic efficiency of field grown
plants. Data are the combined result of three
independent trans-formants (hereafter referred
to as combined) with and without PLGG1 RNAi.
(A) CO2 assim-ilation based on intercellular
[CO2] (Ci).
(B) Combined apparent CO2 compensation
point: Ci* (C) Combined maximum rate of
RuBisCO carboxylation (Vcmax).
62
South et.al., 2019
64. Summary
• The yields need to be improved while the plants are woking at
only 65 to 70 % of their photosynthetic capacity
• Can Hacking Plants Feed the World? Well at least the
Research Looks Good
• Different pathways have been tried, but with limited success
• Bypassing of Photorespiratory pathway has been by far the
most satisfactory hack in terms of field based performance
64
65. Future Perspectives
• The performance of the synthetic glycolate pathway in staple
food crops needs to be evaluated (where seed yield is
economically more important)
• The attempts at combining more than one hack need to be
undertaken for realizing better increment in photosynthetic
efficiency
65