Photosynthesis Test - 9

In long day plants, long photoperiods for initiation of flowering. Here, the long day plant is given 8 hours light, which is less than the critical length. But to compensate that two flashes are given in the middle of the dark period. So, the plant will flower.

Etiolation is a process in flowering plants grown is partial or complete absence of light. It is characterized by long, weak stems; smaller leaves due to longer internodes; and a pale yellow colour (chlorosis).

Because in the boiled water there will be no dissolved salts, which will hamper the uptake of water. So photosynthesis will not take place.

Day neutral plants do not need a specific photoperiod to produce flowers. They are also called intermediates or photoneutrals. Their photoperiod varies from a few hours to 24 hours of uninterrupted light, eg, tomato, cucumber, sunflower, maize and cotton etc.

The phenomenon of photoperiodism was first discovered by Garner and Allard (1920, 22), in tobacco plant. They observed that Maryland Mammoth, the variety of tobacco could be made to flower only by reducing the light hours with artificial darkening. It could be made to remain vegetative in winter by providing extra light.

The important pigments for this system are chlorophyll a 670, chlorophyll a₀ 695 i.e Early electron acceptor of modified chlorophyll in ETC, P₇₀₀, Some physiologist also include carotenes and chlorophyll b in pigment system I. P₇₀₀ act as the reaction centre.

Crassulacean acid metabolism, also known as CAM photosynthesis, is a carbon fixation pathway that evolved in some plants as an adaptation to arid conditions. In a plant using full CAM, the stomata in the leaves remain close during the day to reduce evapotranspiration, but open at night to collect carbon dioxide (CO₂). It occurs in plants with fleshy green leaves and succulents.