Stess in plant during growth and development

1. College Of Agriculture, Gwalior (M.P.)
ASSIGNMENT OF SUBJECT OF
Growth and Development of Horticultural Crops
(FSC-508)
On topic of
Growth and Developmental Process During
Stress
SUBMITTED TO SUBMITTED BY
DR. Rashmi Bajpai Rajveer Singh Katoriya
(Dept .of Horti.) M.Sc. ( Horti.) Vegetable Science
Semester- 2nd , 2017-18
Roll no. – 17111406
INTRODUCTION

2.  The stress concept, originally developedby Hans Selye in1936, has also
been appliedin describing unfavorable andenvironmental constraintsin
plants.
 Thedefinitionof plant stress is, however, quitedifferent fromthe
definitionof stress inanimals and human beings.
 Most authors use the term“plant stress”ina very broad sense, andthis
requires the establishment of a unifying concept of plant stress.
 One should, however, not regardevery littlemodificationandchange of
a metabolic pathway, growthresponse, or development patternof plants
as a stress response, astresseffect, or a stress coping mechanism.
 In other words, the term “stress”shouldnot be appliedto fast
readjustments of metabolic fluxes, photosynthetic rates, or transpiration
rates as inducedby changes inthe photon flux density (sunlight ⇔
clouds), a slight change in temperature, or anincrease or decrease inair
humidity.
DEFINITION OF PLANT STRESS :-
 The original general stress concept for living organisms was developed by Hans Selye
and can be summarized in the following two sentences: “All agents can act as
stressors, producing both stress and specific action,” and “There exist stressor-specific
responses and non-specific general responses.”
 J. Levitt defined stress as: “Any environmental factorpotentially unfavorable to living
organisms.”
 Larcher5 described plant stress as a “state in which increasing demands made upon a
plant lead to an initial destabilization of functions, followed by normalization and
improved resistance,” and also, “If the limits of tolerance are exceeded and the
adaptive capacity is overworked, the result may be permanent damage or even
death.”

3. 1.ABIOTIC STRESS :-
ENVIRONMENTAL STRESS :-
The occurrence of unfavorable environmental factors suchas moisture deficit /
excess, highradiation, lowand high temperature, salinity of water and soil,
nutrient deficiency or toxicity andpollutionof atmosphere, soil and water are
likely toaffect the crop growthin terms of morphology (plant size, architecture,
malformationof plant organs, growth(height, volume, weight), physiological
and metabolic processes andyieldof crop plants.
BIOTIC STRESS :-

4.  Biological stresses differ frommechanical stresses.
 The plants are able to erect barriersbetweenthe body and environmental
stress by expending energy.
 Biological stresses always cause certainamount of injury whichis
irreversibleandis a plastic strain.
 Hence, a biological stress is definedas any environmental factor capable
of inducing a potentially injurious straininliving organisms.
 The living organismmay show physical straine.g. cessationof cytoplasmic
streaming or a chemical straine.g. a shift inmetabolism.
 If the strainis severe, the organismmay suffer a permanent set i.e. injury
or death.
PLANT STRESS HARMONS :-
 Stress may induce common responses suchas enhancement of plant
hormones.
 For instance, wounding can induce the productionof increasedethylene,
auxin, and abscisic acid(ABA).
 Since many kinds of stresses including water, salt, andcoldtemperatures,
induce ABA synthesis, ABAmay be considereda plant stress hormone.
CHEMICAL AND HORMONES RESPONSIBLE FOR STRESS :-
The major hormones producedby plants are auxins, gibberellins (GA),
cytokinins (CK), abscisic acid(ABA), ethylene (ET), salicylic acid(SA), jasmonates
(JA), brassinosteroids (BR) andstrigolactones.
Physiological Effects of Abscisic Acid:

5. 1. Seed and bud dormancy:
Abscisic acidinduces dormancy of buds towards the approach of winter.
Abscisic acidaccumulates inmany seeds during maturationand apparently
contributes toseeddormancy.
2. Senescence:
ABA acts as a general inducer of senescence(Thimann). The onset of senescence
is correlatedwithstomatal closure. The ABA content of aging leaves increases
markedly as senescenceis initiated.
3. Flowering:
In long-day plants, the effect of gibberellins onflowering is counteractedby
ABA, whichaccumulatedin the leaves during the short winter days. This ABA
acts as inhibitor of flowering inlong-day plants. On the other hand ABA induces
flowering inshort-day plants.
4. Starch hydrolysis:
The GA-induced synthesis of a-amylase and other hydrolytic enzymesinbarley
aleurone cells is inhibitedby abscisic acid. This inhibitioncanbe reversedby
increasing the amount of GA supplied.
5.STOMATA CLOSER :
ABA is known to stimulate short-termresponses like closure of stomata.
Role of SA, JA and ET in plant defense response :-
 SA, JA and ET are mainly known to play significant roles inregulating plant
defense responses against various pathogens andpests.
 SA is generally involvedinthe activationof defense response against
biotrophic and hemi-biotrophic pathogens.
 JA and ET are responsible for defense against necrotrophic pathogens
and herbivorous insects

6. FACTORS AFFECTING GROWTH AND DEVELOPMENT DURING STRESS
Natural stress factors:
• highirradiance (photoinhibition, photooxidation)
• heat (increasedtemperature)
• low temperature (chilling)
• suddenand late frost
• water shortage (desiccationproblems)
• natural mineral deficiency (e.g. nitrogenshortage)
• long rainy periods
• insects
• viral, fungal, and bacterial pathogens
Anthropogenic stress factors:
• herbicides, pesticides, fungicides
• air pollutants (e.g., SO2, NO, NO2, NOx)
• ozone (O3) and photochemical smog
• formationof highly reactive oxygenspecies
• (1O2, radicals O2
•– and OH•, H2O2)
• photooxidants (e.g. peroxyacylnitrates)
• acidrain, acid fog, acidmorning dew
• acidpH of soil and water
• mineral deficiency of the soil, ofteninducedby acid rain
• oversupply of nitrogen(dry and wet NO3
- deposits)
• heavy metal load (lead, cadmium, etc.)
• increasedUVradiation(UV-B and UV-A)
• increasedCO2, global climate change

7. Thank you