Agriculture Reference
In-Depth Information
temperatures of new cultivars is very much desirable to prevent damages
by unfavorable temperatures during the plant ontogeny.
10.3
PLANT ADAPTATION TO HEAT STRESS
Plants can be classified into three groups according to the optimum tem-
perature for growth:
(a) Psychrophiles: plants which grow optimally at low temperature
ranges between 0 °C and 10 °C.
(b) Mesophyles: plants whichfavor moderate temperature and grow
well between 10 °C and 30 °C.
(c) Thermophyles: plants which grow well between 30 °C and 65 °C
or even higher (Źróbek-Sokolnik, 2012). Within this group there
are three types of plants: heat-sensitive, relatively heat resistant
and heat tolerant.
Vegetables may be cool season (those tolerant to low temperature
and even frost, for, for example, cabbage, onion, garlic, Brussels sprout,
knolkhol, turnip, radish, etc.) and warm season (those suited for relatively
high temperature, for example, cucurbits, tomato, brinjal, chili, beans,
etc.). Cool season vegetables are heat sensitive crops, while among warm
season crops tomato, brinjal, chili, pumpkin, cucumber, etc., are relatively
heat resistant or warm loving crops and muskmelon, sweet potato, winged
bean, cluster bean, etc., that can tolerate up to 40 °C temperature can be
classed into heat resistant crops.
There is a great variation among the different plants in terms of their
response and tolerance to high temperature. Plants survive in hot and dry
environments by their adaptation mechanisms (Fitter and Hay, 2002).
Avoidance and tolerance mechanisms are the strategies adapted by the
plants to counter heat stress.
10.3.1 AVOIDANCE MECHANISMS
High temperature conditions result in changes in various mechanisms of
plant that include long-term evolutionary phenological and morphologi-
cal adaptations and short-term avoidance or acclimatization mechanisms
such as changing leaf orientation, transpirational cooling, or alteration of
membrane lipid compositions. Closure of stomata and reduced water loss,
