Unit 5 Lesson 3 Understanding Temperature Effects on Plant growth

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Freeze Damage Freezing can cause physical damage to the plant cells. Freeze damage occurs when the cell walls of plants break as the contents of the cells freeze. – Hardier plants are better able to withstand low temperatures than less hardy plants. Freeze damage is very important to the orchard industries in agriculture. –This is especially worrisome with a heavy frost around the time when fruit trees are in flower. –Flowers can be lost from freezing, and hence an entire crop can be lost. To prevent serious damage to crops, growers may choose to spray their crops with water as this offers some protection to the flowers, leaves, and stems. A continuous application of water prevents the temperature of the plant tissues from dropping below 32 degrees F.

Freeze Damage Landscape plants are also susceptible to freeze damage. –If soil temperatures drop too low, roots can be killed and the plants will die. – Landscape plants often have stems, buds, flowers and leaves that are marginally hardy to a frost. –Heavy layers of mulch are often used to help protect delicate landscape plants from damage. Most agricultural crops are herbaceous annual plants and are more easily damaged by cold temperatures. Concern for freeze damage is greatest usually during planting season –before plants are well established –before harvest. To assess frost damage, one must be patient! –It often takes several days to survey the damage and the ability of a crop to recover from the frost.

Freeze Damage Frost Damage on Corn

Heat Damage The effects of heat damage may not be as evident as that of cold; –however it can be as detrimental to crop production causing a loss of Yields aesthetic appeal of crops Heat damage is worst when it is not only hot, but also dry. –Plants have some ability to cool themselves by transpiration through their stomata. As this water evaporates, it has a cooling effect. Stomata close if the plant roots cannot supply water quickly enough to replace water lost from transpiration. –This helps the plant to conserve water. Further water loss causes wilting –a drooping condition and a lack of firmness in the plant tissues. Wilting will result in a loss of turgidity, –or water pressure in the plant cells. –Severe heat conditions can cause plant tissues to dry up and die.

Heat Damage Excess heat usually causes scorch symptoms on leaf tips and interveinal areas. Portions of leaves shaded by other leaves, or leaves on the shady side of the plant, may be undamaged. Frequently, heat damage will occur uniformly over all plants in an affected area