Unit 5 Lesson 3

1. Unit 5Lesson 3 Understanding Temperature Effects on Plant growth

2. Extreme Sport

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8. 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.

9. 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.

10. Freeze Damage Frost Damage on Corn

11. 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.

12. 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