d. Light intensity influences the manufacture of food and development of stem, leaf colour and flowering in plants. An increase in light leads to an increase in the rate of photosynthesis, propionately until the light intensity reaches 10000 lux after which there is no effect. Adaptation: Some plants tend to grow elongated stems with the aim of reaching light faster. Other plants grow towards the source of light. e.g. plants growing in a house grow towards the windows.Plants growing in the thick forests survive by climbing on taller stronger trees to get to sunlight above. Others grow dark green leaves for maximum light absorption. E.g. the philodendron plant. When plants receive less light (eg when days are shorter) they tend to shed some leaves to reduce the us of energy and increase storage.Temperature: Cordial temperature at which photosynthesis can be carried on have a minimum and maximum and optimum, and vary with species. The minimum may be as low as 0c in some artic plants. The optimum for most plants is between 20c and 22c. It may be as high as 45c e.g. the laurel cherry. Too high temperature may increase the rate of water absorption by the plant. This is because the plant has to lose a lot of water through transpiration, to cool itself. Too high temperatures cause drying up of most common plants since their cells get denatured.Adaptation: Succulent plants e.g. cactus have thick leaves with large cells that store water from infrequent rains. They are also covered with a thick cuticle which greatly reduces the evaporation of water. Some plants e.g. thorn trees modify most of their leaves to thorns, to reduce the surface area for transpiration. Some plants such as the golden bells store water and food in underground bulbs and their leaves dry up completely during prolonged period of intense heat and sprout again during the season of reduced heat intensity or wit increase in water supply.Plants growing in areas that experience ...
