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## Modern's Botany (Plant Physiology and Metabolism) B.Sc. II, H.P.U. ### 2. Physiology - Determines how well new cultivars can handle stresses like drought, salinity, heat etc. - Yield improvements are also tracked in this manner. ### 3. Plants - Are like machines, just like car motors and sol...

## Modern's Botany (Plant Physiology and Metabolism) B.Sc. II, H.P.U. ### 2. Physiology - Determines how well new cultivars can handle stresses like drought, salinity, heat etc. - Yield improvements are also tracked in this manner. ### 3. Plants - Are like machines, just like car motors and solar panels. - Materials, energy, and information are in constant flux. - Sugar is made with energy from the sun in the leaves. - Sugar is moved from leaves to the rest of the plant in the form of nutrients. - Water is absorbed from the soil to support growth. - Plant physiology is the study of plants as machines. ### 4. Plant Physiologists - Are obsessed with how plants manage low water conditions. - Plants must expose themselves to the atmosphere (which is dry and acts like a vacuum) in order to get the CO₂ they need for photosynthesis. - Plants must have CO₂ but they are going to lose water along the way. ### 5. Role of Plant Physiology in the Improvement of Varieties - Plant breeders use the method of selection for crop improvement. - Selection on the basis of only external characters is not fruitful. ### 6. Role in Soil Fertility - Our knowledge of mineral nutrition of different crop plants provided extensive revisions in the application of fertilizers. - It is now possible to recommend specific organic fertilizers or inorganic salts using knowledge of plant physiology. ### 7. Role of Gibberellins * **(a) Gibberellins** - Are utilized to break dormancy and induce uniform crop emergence (e.g. seed potatoes) - Enhance the growth of vegetative parts of several floricultural species and are used to increase flower size * **(b) Gibberellins** - Produce parthenocarpic (seedless) fruits. * **(c) Cytokinins** - Have less importance in agriculture. - Are used in extending self-life of lettuce, tomatoes, apples etc. - Induce efficient root system in maize and rice. ### 8. Role of Ethylene * **(a) Ethylene** - Is a hormone which is known to cause fruit ripening * **(b) Ethylene** - Causes abscission * **(c) Ethylene** - Is used to induce bulbing in onion * **(d) Ethylene** - Increases tillering in rye, peas, etc. ### 9. Role Of Inhibitors: * **(a) A familiar inhibitor CCC (2-chloroethyl- trimethyl ammonium chloride)** - Is used to induce stiffening of plants, enhances number of roots and litters, checks lodging and increase yield in wheat, oat and several strains of Secale (rye). * **(b) CCC** - Is also used to increase bolting, flowering, and increase yield in cotton. * **(c) Many inhibitors, such as, CCC, phosphon, B-9, etc** - Are used in ornamental horticulture to retard the height of plants like chrysanthemum. ### Applications of Plant Physiology * **10. Role in Seed Production:** - Knowledge of plant physiology helps in separating seeds from weeds * **11. Role in Food Processing:** - Plant physiologists are involved in the study of food processing, storage, and preservation of food. ### Horticulture - It is the intensive cultivation of plants. - Includes the cultivation, science and art. ### Areas of Horticulture: * **(i) Pomology:** - Peach, cherry, plum, apple, pear, etc. * **(ii) Vegetable Gardening:** - (Tomato, potato, etc). * **(iii) Floriculture:** - For landscape and other purposes * **(iv) Environmental Horticulture:** - Deals with the cultivation and management of ornamental plants. ### Role of Temperature: * **1. Premature Flowering:** - Many biennials normally flower in the second year after planting. * **2. Development of Perennial plants:** - Perennial plants require a chilling period which is part of the temperature requirements. - Freezing temperatures are suitable for many plants but not cold. - In case temperature is not so low for a longer period, the plant may not flower and dies. * **3. Carbohydrate metabolism:** - Plants tissues are generally more susceptible to winter chilling. - Susceptibility of plant tissues to winter injury is increased at higher temperatures. - Plants that are in a dormant condition during the winter are less susceptible to cold and other storage problems. * **4. Frost Hardening:** - In heavy frosts, temperatures fall well below freezing point. - Due to lower temperatures, cells become turgid and develop a large amount of water in them. - This water freezes and expands. - Ice crystals, which are formed within the cells, break the protoplasm. * **5. Winter Cover:** - Is called `phytophysical winter cover`. - The wind can damage the stems of evergreens, plants with needles and branches. - To provide a winter cover, the pruned branches are spread over the sensitive plants.