Unit 5Lesson 3

Understanding Temperature Effects on Plant growth

Extreme Sport

Extreme Sport

Extreme Sport

Extreme Sport

Extreme Sport

Extreme Sport

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