Cold stress

Cold stress preparation by abdulla hama najeb

CONTENTS

AbstractCold temperature .determentDamage of cold Chilling injury musaSymptoms of Freezing injury

IntroductionChilling Affects on plantsCauses of Chilling injuryFreezing 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

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AbstractPlants 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.preparation by abdulla hama najeb 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 (015 C) and freezing ( 0 C ) Plant chilling injury refers to an injury that is caused by a temperature drop to below 15C but above the freezing point.Freezing ; it is (T < 0 C ) Freezing injury in plants can be from two sources: Freezing of soil water, and; Freezing of the fluids within the plant. preparation by abdulla hama najeb 5

Chilling Affects on plantsinjury 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 preparation by abdulla hama najeb 6

Damage of cold Depends of many factors .Development stage Duration / severity of frostRates of cooling

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Causes of Chilling injuryThe 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. preparation by abdulla hama najeb 8

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Freezing injury Two types of freezing occur in plant cells and tissuesvitrification : 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 preparation by abdulla hama najeb 10

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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. preparation by abdulla hama najeb 12

INCREASED CHLOROPHYLLpreparation by abdulla hama najeb 13

abdulla hamasalah (ah) - Low temperature inhibits chlorophyll accumulations in actively growing leaves. In rice, cold tolerant lines, for example, japonica accumulates more chlorophyll under cold stress than do cold sensitive line, for example of indica rice [18]. Rasolofo [19] evaluated 181 accessions to identify donor and outstanding cold tolerant lines using leaf discolouration score (1-3) and found 19 remained green (dark) after 10 days in the 12 oC cold water tank. Sanghera et al. [17] found 18 cold tolerance IRCTN rice genotypes based on dark green colour and high spikelet fertility (>90%) under temperate conditionsPreventions & Protection1. 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. preparation by abdulla hama najeb 14

hardening off tomatoes in cold frames

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2. SOIL BANKING .It consists of placing a mound of soil around the trees 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

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Preventions & Protection

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.

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Preventions & Protection

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 2C 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. preparation by abdulla hama najeb 18

Preventions & Protection

5. Fogging Fog also retards the loss of heat from soil and plant surfaces to the atmosphere Fog can provide up to 4C of protection outdoors during radiational cooling

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Preventions & Protection

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 54C), not hot water, in enclosed growing and/or storage areas is effective to prevent cold injuriespreparation by abdulla hama najeb 20

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Referenceshttp://www.ncbi.nlm.nih.gov/pmc/articles/PMC3129041/Physiology and Molecular Biology of Stress Tolerance in Plants bookCold 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 acclimationhttp://www.slideshare.net/rajeshdebnath545/chilling-freezing-injuries-of-crops

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