Cold stress

COLD STRESS
preparation by abdulla hama
najeb

CONTENTS
• Abstract
• Cold temperature .determent
• Damage of cold
• Chilling injury musa
• Symptoms of Freezing injury
• Introduction
• Chilling Affects on plants
• Causes of Chilling injury
• Freezing injury Two types of
freezing occur in plant cells and
tissues
• Preventions & Protection by
A . Cold hardening B . SOIL BANKING
C . Wrapping D . Sprinkling
E . Fogging F . Air movement
preparation by abdulla hama najeb
2

ABSTRACT
• Plants are constantly exposed to a variety of environmental stresses.
Freezing or extremely low temperature constitutes a key factor
influencing plant growth, development and crop productivity. Plants
have evolved a mechanism to enhance tolerance to freezing during
exposure to periods of low, but non-freezing temperatures. This
phenomenon is called cold acclimation. During cold acclimation, plants
develop several mechanisms to minimize potential damages caused by
low temperature. Cold response is highly complex process that involves
an array of physiological and biochemical modifications.
3

INTRODUCTION
• Only one-third of the total land area on Earth is free of ice and 42% of land
experiences temperatures below −20 °C. In such areas, plants require
specialized mechanisms to survive exposure to low temperature. Cold stress
can be classified as chilling (0–15 °C) and freezing (<0 °C) stresses. Generally,
plants originating from temperate regions, such as spinach and Arabidopsis,
exhibit a variable degree of chilling tolerance and can increase their freezing
tolerance during exposure to chilling and non-freezing temperatures. This
process is known as cold acclimation . On the other hand, plants of tropical
and subtropical origins are sensitive to chilling stress and lack the cold
acclimation mechanism.
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1. Chilling ; it is ( T > 0 C ) Plant chilling injury refers to an
injury that is caused by a temperature drop to below 15°C
but above the freezing point.
2. Freezing ; it is (T < 0 C ) Freezing injury in plants can be
from two sources:
A. Freezing of soil water, and;
B. Freezing of the fluids within the plant.
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CHILLING AFFECTS ON PLANTS
• injury causes several metabolic of physiological dysfunctions to
the plant including •
• disruption of the conversion of starch to sugars (amylotytic
activity) •
• decreased carbon dioxide exchange •
• reduction in net photosynthesis •
• the destruction/degradation of chlorophyll
6

DAMAGE OF COLD
Depends of many factors .
1. Development stage
2. Duration / severity of frost
3. Rates of cooling
7

CAUSES OF CHILLING INJURY
• The primary cause has been found to be the opening (and locking)
of the leaf stomata when the permeability of the roots to water is
low •
• The leaves lose water faster than it can be replaced and they
become dehydrated.. •
• In some plants, the stomata behave properly at chilling
temperatures and the injury is said to be metabolic •
• A decrease in respiration, photosynthesis and fatty acid synthesis
may all contribute to the chill-starvation of some plants.
8

9

FREEZING INJURY TWO TYPES OF
FREEZING OCCUR IN PLANT CELLS AND
TISSUES
• vitrification : Solidification of the cellular content into noncrystalline
state. It occurs by rapid freezing of cells to a very low temperature .
• Crystallization / ice formation : Crystallization of ice occur either
extracellularly or intracellularly
10

11

SYMPTOMS OF FREEZING INJURY
• Desiccation or burning of foliage
• Water-soaked areas that progress to necrotic spots on leaves, stems or fruit and
death of sections of the plant or the entire plant.
• Close examination of woody plants several days or weeks after freezing may
reveal a dead or weakened root system or split bark on stems or branches.
• Obvious symptoms on plant foliage may not be present until after the plant has
been stressed by warm temperatures.
• A hot, bright day could increase transpirational water loss beyond the ability of
injured roots or stem conductive tissue to replace.
• Wilting and/or desiccation, as caused by direct drought stress.
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INCREASED CHLOROPHYLL
13

PREVENTIONS & PROTECTION
1. Cold hardening
Cold hardening alters the behavior of the stomata so
that they close under the same conditions; the root
permeability is also increased.
Cold hardening affects the lipid content of cell
membranes and has been found to lower the optimum
temperature for photosynthesis and respiration.
14

hardening off tomatoes in cold frames preparation by abdulla hama
najeb
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2. SOIL BANKING .
• It consists of placing a mound of soil around the
tree’s trunk to protect the bud union and trunk
from cold.
• One of the most efficient cold protection
methods for young trees and has been used with
success for many years
Preventions & Protection
preparation by abdulla hama najeb 16

3. Wrapping
• Most tree wraps can be attached anytime
during the year and left on the tree
throughout the year or even for several
years.
• When freeze damage occurs, wraps
should be removed or pushed down to
allow for growth of new shoots.
• Wraps should be properly positioned and
fastened around the trunk for best results.
• It is important to cover the entire lower
trunk, especially at the base.
17

4 .Sprinkling
• It can be used to moderate temperatures above freezing
because of sensible heat in water and can maintain plant leaf
temperature at 1 to 2°C degrees or more.
• Water applied to aisles of shade structures or greenhouses
increases the moisture content of the air and soil surrounding
the plants, thus slowing the rate of temperature drop.
• The water absorbs heat during the day which is released slowly
at night.
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5. Fogging
• Fog also retards the loss
of heat from soil and
plant surfaces to the
atmosphere
• Fog can provide up to
4°C of protection
outdoors during
radiational cooling
19

6. Supplementary Heat supply Air movement method:
• Wind machines have been used for many years in citrus and
vegetable industries and recently in the ornamental industry as a
means of cold protection •Air movement also helps distribute and
circulate heat added by orchard heaters or other sources. Warm
water movement:
• Circulation of warm water (43 to 54°C), not hot water, in enclosed
growing and/or storage areas is effective to prevent cold injuries
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THANK YOU
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REFERENCES
• http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3129041/
• Physiology and Molecular Biology of Stress Tolerance in Plants book
• Cold Signaling and Cold Response in Plants . (ARTICLE)
• MORPHO-PHYSIOLOGICAL TRAITS ASSOCIATED WITH COLD STRESS
TOLERANCE IN TROPICAL MAIZE (ZEA MAYS L.) (ARTICLE)
• Physiological and Metabolic Responses of Winter Wheat to Prolonged
Freezing Stress‘ (ARTICLE)
• REVIEW ARTICLE .Cold stress and acclimation
• http://www.slideshare.net/rajeshdebnath545/chilling-freezing-
injuries-of-crops
preparation by abdulla hama najeb 22

Cold stress

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