The physiology of photosynthesis / by Sir Jagadis Chunder Bose.

  • Jagadish Chandra Bose
Date:
1924
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Licence: In copyright

Credit: The physiology of photosynthesis / by Sir Jagadis Chunder Bose. Source: Wellcome Collection.

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    give concordant results. The loss at 220 C. is about 4 per cent. The temperature-coefficient is determined on the Differential Method by the formula The value of the coefficient is about 20. The photosyn- thetic activity of Hydrilla becomes doubled under a rise of temperature of 70 C. The activity at a higher temperature is found by the formula Ax = A/ + K (T — t) The Tonic Factor in Photosynthesis The condition of a plant can be gauged by the Tono- meter ; the ratio of response to stimulus measures the physiological tone of the plant. In photosynthesis the ratio, K, is found by dividing the increment of activity by the increment of the factor which induces it. The tonic condition of a plant is modified by seasonal variation, by traces of chemical substances, by the starch- and chlorophyll-content of the cell, and by the action of stimulus. Seasonal variation exerts a considerable influence on the tonic condition ; the photosynthetic coefficient in spring is nearly double that in winter. Infinitesimal traces of certain chemical substances induce a heightening of the tonic level as seen in the great enhance- ment in the rate of photosynthesis (p. 71). The photosynthetic activity is greater in a young leaf than in a very young or old leaf. The chlorophyll-content is at its maximum in a young leaf. In a sub-tonic specimen, stimulus stirs up the rela- tively inert tissue to activity. The tonicity is raised and the response becomes enhanced. In a vigorous specimen,
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