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## MODERN’S BOTANY (PLANT PHYSIOLOGY AND METABOLISM) B.Sc. H.PU ### APPLICATIONS OF LOW TEMPERATURE - **Spring frost.** Cold temperature will freeze under transplants emerging seedlings and opening buds in the spring. Fruit buds are easily frozen once they start expanding. The cold spots are calle...

## MODERN’S BOTANY (PLANT PHYSIOLOGY AND METABOLISM) B.Sc. H.PU ### APPLICATIONS OF LOW TEMPERATURE - **Spring frost.** Cold temperature will freeze under transplants emerging seedlings and opening buds in the spring. Fruit buds are easily frozen once they start expanding. The cold spots are called "Frost pockets" and many lead to cold damage to plants in the area. - **Mulching.** A covering of mulch is used to modify soil temperature. It is applied soon after the ground freezes in the early winter, mulch will keep the soil frozen and the covered plant crowns at a consistent cold temperature to prevent winter damage. - **Modification of low temperature using covers or heat sinks.** Plants are surrounded with medium to large-sized rocks to absorb heat or cover them with fabric row covers, plastic sheeting, or waxed paper cloches in winters. - **Use of heaters and fans.** Protecting trees fruits from early forests can be carried out in orchards using heaters or large fans. - **Sprinkling.** Water is sprinkled on plants as they cool, the heat of freezing will keep the plant surface at or near safe temperature. ### ROLE OF LIGHT IN HORTICULTURE 1. **Light quality.** The following types of rays are used by plants in Physiological processes: - **Violet.** These are required for the development of pigments in plants. Indigo and violet rays are also used for bending flower heads and other plant parts toward the sun (phototropism). - **Blue-violet and orange-red.** Such rays provide the light energy for photosynthesis. - **Orange-red and far-red (long than red).** It is absorbed by plants and produces the day length response (photoperiodism). 2. **Light intensity.** Tropical plants, like many of our house plants, thrive in nature under a jungle canopy that provides very low light intensity. Plant not from the jungle are able to grow in and use very bright or intense light. Most crop plants use about 1,200 foot-candles of light, but they will grow better in light upto 4,000 foot candles because of shading from surrounding leaves. Little light will cause plants to stretch and become "gangly" or usually long. Nodes will be far apart, leaves broad and thin, and the plants will have a loose, open structure. Reduced light intensity can also induced succulence. 3. **Light Duration.** Plants respond to particular day length. - **Long-day Plants.** In a long-day-plant and, if planted late in the winter, it will make a flower stalk before producing leaves.