Temperature: An Ecological Factor

Temperature Temperature is the measurement of heat in degrees centigrade/Fahrenheit/Kelvin. The temperature at which physiological processes are at their maximum efficiency is called optimum temperature. The minimum, optimum, and maximum temperatures are called cardinal temperatures. The distribution of plants is also influenced by temperature variations.   Variations Depending upon the response of plants to temperature variation of environment, the entire vegetation of Earth can be divided into following 4 classes: Megatherms Mesotherms Microtherms Hekistotherms Megatherms These are the plants which require more or less high temperature throughout the year for their optimal growth and development. Example: Dominant vegetation of tropical rain forests Mesotherms These plants are capable of enduring lower temperatures during some period of year, followed by high temperature. Example: Vegetation of tropical deciduous forests Microtherms These plants are incapable of enduring high temperatures even for a few months of the year. Example: mixed coniferous forests Hekistotherms These are cold-tolerant plants of polar regions. Effects of Temperature on Plants Temperature plays an important role in the morphology, physiology, metabolism, growth, and development of plants, which affects the cell. At extremely low temperatures, the cell may die or denature. At extremely high temperatures, the protein may denature or coagulate. Temperature affects the metabolic rate. An increase in temperature leads to an increase in metabolic rate. Respiration is also affected by temperature. The rate of respiration usually doubles with an increase in temperature. The growth and development of plants are regulated by variation in temperature. At optimum temperature, the growth and development of plants is maximum. Transpiration is also influenced by variation in temperature. The rate of transpiration increases with the increase in temperature and decreases with the decrease in temperature. Adaptations of Plants to Temperature Variation Many plants have various adaptations to guard against thermal variation. During winters at low temperatures, in some plants, the insoluble organic reserves may transform into dissolved substances to prevent plant from lethal injury. In certain cases, plants develop special structures such as bud scales, hairy envelope, etc. to guard against thermal variation. Wind: An Ecological Factor Air in motion is called wind. Wind is an important ecological factor which affects plant life both directly and indirectly. The direct effects of wind often cause violent winds which break off twigs or branches of plants and sometimes even uproot trees and shrubs. Wind is directly involved in transpiration, mechanical damage, and dissemination of pollen, seeds, and fruits. The velocity of wind is affected by various factors such as geographic situation, topography, vegetation, position, etc. Effects Wind brings about a number of physical, anatomical, and physiological effects on plants. Physical effects include breakage and uprooting of trees, deformation, lodging (wind injury common in grasses), erosion, and deposition of salt spray, etc. These physical effects of wind affect the trees in a large extent causing damage to it. Anatomical and physiological effects involve dessication, dwarfing, development of certain structures, etc. Adaptations of Plants to Wind Plants develop various adaptations in response to the damage caused due to wind. Larger plants which are often exposed to violent winds have following adaptations: Their trunks and branches are often bent. The branching is irregular. The crown presents a very peculiar shape. The leaves are smaller than usual. Sometimes fast, cold winds result in cushioned growth in plants. Plants growing in strong wind areas develop special shapes for resistance to wind. Plants growing at higher altitudes show stunted growth. Plants growing at lower altitudes have less chances to being affected by wind. Bush growing on high mountains develop underground rhizomes and root system, and its aerial branches do not project much higher above the soil surface.