ABSTRACT
Plants growing in natural environments are constantly subjected to various environmental stresses. Environmental stresses can be from the soil, including soil physical constraints and chemical stress such as nutrient deficiency and toxicity, and can also be from the atmosphere, such as temperature, moisture, air pollutants, and light. High temperature is a primary stress limiting the growth of cool-season plant species during the summer. The problem of high-temperature stress is expected to accentuate in the future as global temperature is projected to rise 1 to 4.5
°
C in the next 50 years [1]. It seems likely that throughout most of the temperate zone there will be longer warm periods and hotter extremes, which could intensify heat-stress injury in many cool-season plant species. Low temperatures typically occur during winter, late fall, and early spring in cold climatic regions. Chilling or freezing is a major stress threatening the growth of warm-season plants. Drought stress has a global impact, which limits the growth of both coolseason and warm-season plant species. Water deficit due to lack of water supply or drought stress is often associated with salinity, winter desiccation, and heat stress. Water stress can become more significant as water becomes increasingly limited for irrigation.
