plant physiology

Mineral Nutrition History In remote pasts, it was realized that the land plant obtained nourishment from soils through their roots. This idea was supported by the common practice of additions of animals and plant manures to the soils for increasing the productivity of the crops. Only during the first half of the 19th century botanists began to understand that the ...

Significance of Transpiration Transpiration is potentially harmful process in the following ways:  Water is of vital importance to plants. The plants expand huge amount of energy in absorbing water from the soil, but       the loss of water by transpiration results in tremendous energy.  Under conditions of deficient water supply the enormous loss of water by transpiration causes ...

Factors Affecting the Rate of Transpiration The rate transpiration is affected by a number of environmental (external) and plant (internal) factors. These factors also affect the stomatal movements. Effect of Environmental factors The environmental factors such as humidity (vapour pressure), temperature, air movements (wind), atmospheric pressure, light and availability of soil water influence the rate of transpiration most. Effect of ...

Theories Of Stomatal Movement Various theories have been put forward to explain the change in osmotic potential of the guard cells. Photosynthesis in Guard Cells Guard cells contain chloroplasts, they synthesize sugar during day time that causes increase in osmotic potential of the guard cells and a subsequent increase in turgor pressure. At night, the sugar is converted into starch ...

Stomatal Regulation of Transpiration Since the aerial surfaces of land plants are in direct contact with atmosphere they face the problem of evaporation, which may lead to death because of dehydration. To overcome this problem their aerial surfaces are covered with thick cuticle. But the cuticle blocks exchange of essential gases, the oxygen and carbon dioxide. To facilitate exchange of ...

Nastic Movements A growth or turgor movement of a plant organ in response to an external stimulus, mostly light intensity and temperature, in which the direction of the response is not determined by the direction of the stimulus. The direction of the movement is determined by the structure of the responding organ. The nasties are brought about by growth resembling ...

Geotropism When plants are placed horizontally they exhibit growth response to the stimulus of one-sided gravity. It is called geotropism or gravitropism. The tip of the stem grows away from the pull of the gravity (negative geotropism) and the root tips grow towards it (positive geotropism). The plant responses to unilateral gravity are growth movements because the resulting curvatures occurs ...

Plant Movement It is a characteristics of plants, except for few unicellular plants such as Chlaymydomonas, that they do not exhibit movement of entire organism (locomotion). However, individual plant organs (stems, roots and leaves) exhibit movements. These movements are triggered in response to external environmental stimuli or by an internal timing mechanism, the biological clock. Therefore, these movements are also ...

Nature of Vernalization Stimulus – Vernalin or Gibberellin Many attempts were made to isolate vernalin but all failed. However, Anton Lang in 1957 showed that application of gibberellins to certain vernalization requiring biennials like henbane induce flowering in them without cold temperature treatment. Purvis in 1961 induced winter annuals to flowers induced by treating their seeds with gibberellins. It was ...

Vernalization Vernalization is a process that promotes flowering by cold temperature treatment given to a seed that has imbibed water or to a growing a plant. Like photoperiodism, vernalization is also an inductive effect leading to flowering sometime after the cold temperature treatment. If cold temperature treatment is not provided to cold requiring plants they may either show delayed flowering ...