The document discusses Water Use Efficiency (WUE) in plants, emphasizing its significance in agriculture amidst increasing global food demand and limited water resources. It outlines key plant mechanisms and management practices that influence WUE, including physiological traits and innovative agricultural techniques like drip irrigation and conservation tillage. Case studies illustrate the impact of deficit irrigation on WUE in crops like wheat, chickpea, and lentil, while suggesting future research directions to enhance crop water efficiency.

1. PHYSIOLOGY BEHIND WATER USE EFFICIENCY
IN PLANTS
UJJWAL KUMAR
(M-PLPH-00741-BAC-2020-21)
Department of Plant Physiology and Biochemistry
Bihar Agricultural University
Sabour-81320, Bihar

2. Contents
Introduction
Importance in agriculture
Plant parts that influence WUE
Factors influencing WUE
Case Study – 01 (Physiological mechanism contributing to the increased
water-use efficiency in winter wheat under deficit irrigation.)
Case Study – 02 (Water use and water use efficiency of chick pea and
lentil in a Mediterranean environment.)
Conclusion
Future scope of research

3. Introduction
 Water use efficiency (WUE) is a concept introduced by Briggs and Shantz
(1913), depicting a relationship between plant productivity and water use.
 Efficiency means output of any substance or any material per unit input.
WUE can be described in the following two ways
1. Field water use efficiency:- This may be defined as the ratio of the
amount of economic crop yield to the amount of water required for crop
growing.
Mathematically, WUEf = Y/ ET+(G)+ (D)
Where WUEf is field water use efficiency (kg/ha mm), Y is the yield of
marketable crop (kg/ha) and WR is the water requirement (mm).
 Water use efficiency is determined to evaluate the benefit of applied water
through economic crop production.
Percolation loss
loss in metabolic process

4. Contd….
 2. Crop water use efficiency:- Crop water use efficiency is defined here as yield of
plant product (Y) per unit of crop water consumptively used by the crop.
Mathematically, WUEc = Y/ ET+(G)
Where WUEc is crop water use efficiency (kg/ha mm), Y is the yield of marketable
crop (kg/ha) and ET is the evapotranspiration (mm), CU is consumptive use (mm).
Water-use efficiency (WUE) is defined as a ratio of biomass accumulation, ex-
pressed as carbon dioxide assimilation, total crop biomass or crop grain yield to
water consumed, expressed as transpiration (T), evapotranspiration (ET), or total
water input to the system.
loss in metabolic process

5. The imbalance between rising food demand and insufficient
water supply for agriculture is a global issue.
The continuous growth of the world population poses a great
threat to global food supply and water security.
FAO has warned that global food production has to be
increased by 70% by 2050 to ensure food security while
increasing food production requires more agricultural water
use.
Water security is the foundation of food security, as water
shortage will directly lead to fluctuation of food production.
Importance in agriculture

6. Contd..
 It is possible to increase WUE in a field without increasing water
supply by altering the mechanisms that control WUE in plants
 Thus, improving plant water use efficiency (WUE) has become a
major goal for the near future.
 To save water for future generations and increase crop production by
using less water, water-use efficient crops/varieties are needed along
with integrated management techniques.
 The major objective of any agriculture-based research should be
maximum production per drop of water applied.
Agriculture is the major water consumption sector, accounting for
more than 70% of total water use worldwide. It is unsustainable to
increase food production simply by expanding agricultural water use,
hence saving water in agriculture becomes a necessary part of the
solution.

7. Plant parts that influence WUE
Leaf size and
orientation
Leaf morphology
Leaf anatomy
Plant Canopy
Stem anatomy
Root system

8. Canopy Size
Canopy Size influence WUE through its effects on ET
 Affects light interception and
reflectance, such that erectophile
canopies with leaves more vertically
orientated allow greater light
penetration and reflectance during the
day due to the angle of the sun,
compared with planophile canopies
where leaves are orientated more in a
horizontal plane (Yunasa et al.,1993).
 More closed canopy will have higher
humidity thus lower temp. than outer
environment .
 Evaporation may be greater early in the season, before the canopy has fully
established, depending on temperature and relative humidity. The trait for early
vigor may be a way of establishing canopy cover quicker to minimize soil
evaporation (Botwright et al., 2002).
Erectophile
planophile
Erectophile
planophile

9. Stomata are important determinant of WUE, being physically located as
the gateway controlling the trade-off between carbon capture and water
loss. The more stomata per unit area (stomata
density) the more CO2 can be taken up, and
the more water can be released.
Stomata Influencing WUE

10.  Stem support the leaves in conduction of water and minerals, where they can be
converted into usable products by photosynthesis; and pholem transport these
products from the leaves to other parts of the plant, including the roots.
Stem Influencing WUE
Xylem
Pholem
 Food & water also stored in
stem such as tubers, rhizomes
& corms.
 Xylem no. varies inside
vascular bundle species to
species.
 Xylem vessels are analogous
to pipe and abundance and
diameter of xylem vessels
determine the hydraulic
conductance in plant.

11. Root are the first to sense drought and
adjust their genetic program according
to the level of stress.
Roots have hydraulic properties which
conduct water from soil surface to
xylem. More hydraulic properties plants
have more WUE.
Monocot roots absorb water just behind
the root tip and dicots absorb from
entire root length.
In case of drought stress, increase in no.
of branches in monocot or increase in
length of root in dicots, WUE can be
increased .
Fibrous roots
Tap roots
Roots influences WUE

12. ABA (Abscisic acid): is an important stress hormone produced in the
roots as the soil dries and is transported in the xylem to the leaves where
it closes the stomata .
It also induces a reduction
in leaf growth an increase
in root growth at low
water potentials and an
increase in the hydraulic
conductivity of roots all.
 ABA production has
been shown to increase
yields of wheat under
moderate stress
conditions (Travaglia et
al., 2010)
Stress hormone influencing WUE
ABA
ABA
ABA

13. (Bramley et al., 2010)
Genes Influencing WUE

14. Agronomic Management Practices that influences WUE
Conservation tillage: soil is not tilled and exposed to the drying so,
moisture is retained within the soil and new crop is generally planted
directly into the stubble of the previous crop.
Mulching: the placement of any
organic or inorganic material
over the top of a soil surface to
protect soil moisture.
Moisture stress
Wilted plant

15. Contd….
Intercropping: in rainfed conditions the total water used in intercropping system is
almost the same as for sole crops, but yields are increased, thus water use efficiency is
higher than sole crops.
Direct Seeded Rice (DSR): It is
an efficient method of water saving
in rice. DSR can give equivalent
yield as puddled transplanted rice.
puddled transplanted rice required
20 % more water than DSR at
establishment & vegetative
phase.(Jat et al., 2006).

16. Contd….
 Weed control: the water and nutrient requirement of weeds is greater
than that of crop plants.
Drip irrigation is a type of micro-irrigation system which supply
water directly into the root zone and minimize evaporation.
It saves up to 90 % of water compression to flood irrigation.

17. Contd.
 Chemical Methods: Reducing transpiration is the most effective means of
increasing the amount of water available to the crop.
 Anti-transpirent: that are used to reduce the transpiration either by closing the
stomata or by forming the film on the leaf surface.
 Stomatal closing type: phenyl mercuric acetate (PMA) and herbicides like
Atrazine in low concentration serve as anti-transpirants by inducing stomatal
closing.
 Film forming type: Plastic and waxy material which form a thin film on the leaf
surface and result into physical barrier. Ex- foliate.
 Reflectance type: They are white materials which form a coating on the leaves and
increase the leaf reflectance . Ex- kaolin
 Growth retardant: reduce shoot growth and increase root growth and thus enable
the plants to resist drought. Ex Cycocel
The most common type of anti-transpirants are of four types:

18. Contd….
Crop
Water
requirement
(mm)
Grain Yield
(kg/ha.)
WUE (kg/ha.-
mm)
Rice 2000 6000 3.0
Sorghum 500 4500 9.0
Pearl millet 500 4000 8.0
Maize 625 5000 8.0
Groundnut 506 4680 9.2
Finger millet 310 4137 13.4
Sugarcane 1700 10000 5.88
Jute 480 2800 5.8
Sunflower 400 2000 5.0
Green gram 250 1000 4.0
Mustard 300 1400 4.7

19. Climatic Conditions: affects both crop yield and evapo-transpiration
Temperature: an increase in temperature
brings about an increase in the rate of
evapo-transpiration.
Relative humidity: when the
relative humidity is high, the
rate of evapo-transpiration
decreases. because the
atmosphere is saturated with
moisture.
Solar radiation: Incident solar
radiation and adverted heat
provide energy for the
evaporative process.
Wind velocity: when the wind is stagnant the rate of ET remains normal, when it is
blowing gently the rate increases because it removes moisture from the vicinity and
when the wind is blowing violently the rate of transpiration decreases because it creates
hindrances in the outward diffusion of water vapours from the transpiring parts due to
closing of the stomata.
Climatic factors

20. Edaphic factors
 Inadequate supply of soil moisture as well as excess moisture supply
to the crop have an adverse effect on plant growth and productivity
therefore conducive to low WUE.
Soil moisture content

21. Soil texture
Water molecules hold more tightly to the fine particles of a clay soil
than to coarser particles of a sandy soil, so clays generally retain more
water.
A soil with a high percentage of silt and clay particles have higher
water-holding capacity.
Organic matter percentage increases, the water-holding.

22. Soil structure

23. Case Studies 01
Site United States Department of Agriculture (USDA-ARS),
Bushland, Texas
Duration 3 Consecutive seasons 2009,dry season(DS); 2009, wet season
(WS); 2010 and dry season (DS) in the same field)
Wheat cultivar (Triticum aestivum L.) cultivar TAM-202
Design CRD ( Completely Randomised Design)
Treatments 9
Replication 6
Irrigation treatments At different developmental stages
Data recorded At initial and every 7-10 days interval till physiological maturity

24. Objectives:-
(a) Determinations of grain yield and water-use efficiency (WUE)
under deficit irrigation.
(b) To Investigate the effect of deficit irrigation on dry matter
accumulation and remobilization of carbon reserves during grain filling.

25. Contd..
Table 1. Irrigation scheduling and the amount of water application (mm) at
different treatments (TRT)
Table 2. Summary of temperature and precipitation data

26. Contd..
Figure 2. The seasonal changes of plant leaf water potential (Cw)
among treatments
DOS
DOS

27. Figure 3. The seasonal changes of plant photosynthetic rate (Pn) (A)
and stomatal conductance (Gs) (B) in rainfed (T-1), three one-irrigation
treatments (T-2, T-3, and T-4), and three-irrigation treatment (T-8).
DOS DOS

28. Conclusions
It was observed that deficit irrigation significantly increased
grain yield and WUE as compared to rainfed.
The increment in the WUE under deficit irrigation was
contributed by increased HI and resultant was that photosynthesis
and biomass were reduced by water stress during grain filling.

29. Case Studies 02
Site ICARDA, Tel Hadya, Northern Syria
Cropping
pattern
Chickpea- durum Wheat (2-course crop rotation along with 6 other
alternative crops) and Lentil-Wheat ( 2-phase rotation)
Design Split-plot
Replication 3
Seedlings 14 days old and manually transplanted at spacing of (20*20 )cm
Varieties Syrian local small (1986-1993), Idleb 1 (1994-1995) and ILL5883 (1996-
1998

30. Water use by Chickpea and lentil
Fig- Seasonal change in soil water storage for Chickpea and lentil in 3
seasons, Dry(1989-90,O), Average(1991-92, ) and Wet( 1997-98,∆)
seasons from the rainfed treatment to supplemental irrigation.
wet wet

31. Contd…
Fig- Seasonal change in accumulated evapotranspiration (ET) for
Chickpea and lentil in 3 seasons, Dry(1989-90,O), Average(1991-92, )
and Wet( 1997-98,∆)
chickpea lentil

32. Contd…
• Fig:- Evapotranspiration(ET,mm), Water use efficiency for grain
yield(WUEgr, Kg/ha.mm), and water use efficiency for dry
matter(WUEdm, Kg/ha.mm) from the 2-course crop rotation (Wheat-
Chickpea; wheat-Lentil) experiments over 12 seasons at Tel Hadya, Syria.

33. Conclusion
 In this long experiments, found that lentil was better adapted to
Mediterranean environments than chickpea as we have seen in
the previous figure in terms of dry matter and therefore higher
water use efficiency.

34. Conclusion
 The strategy is expected to save water, improve quality, and
increase efficiency, and be the approach for achieving
modern sustainable water-saving agriculture in the future.
 Water-efficient genotypes can be tailored based on well-
suited canopy size and orientation, leaf morphology,
orientation and anatomy, and root architecture to improve
WUE.

35. Future Scope of Research
 To identify crops’ drought tolerance genes to help screen out and
develop new varieties capable of saving water or high-efficient water
use.
 investigate the relations between WUE and various physiological
processes based to understand the key processes controlling crop
WUE.
 To examine the relationships and relative importance of WUE with
soil water, nutrients, gases, heat, and crop planting structure and
density, root-shoot ratio, and rhizosphere microorganisms to
coordinated WUE improvement solution.
In the future, further studies are needed in

36. Thank you

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