The physiology of photosynthesis / by Sir Jagadis Chunder Bose.

  • Bose, Jagadis Chandra, 1858-1937.
Date:
1924
Catalogue details

Licence: In copyright

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

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    THE PHYSIOLOGICAL FACTOR IN PHOTOSYNTHESIS The anabolic and catabolic processes A and D—External manifestations of A and D effects—Photosynthetic and phototropic curves—De- pendence of maximum response on the intensity of stimulus—■Effect of variation of temperature—D effect due to shock-stimulus—Pheno- menon of alternating response—Dual effects of stimulus of light—• Unmasking of the A effect—Effect of chemical agents—Effect of tonic condition on response. The process of photosynthesis begins with a photochemical reaction in which C02 and H20 are synthetised into some form of organic matter such as formaldehyde. To what extent this is effected, as a purely physico-chemical process, by the chlorophyll proper is still uncertain. Baly and Heilbron have recently shown that * in the presence of a suitable basic coloured substance, such as malachite green, with which the carbonic acid can combine loosely, the formation of formaldehyde can be demonstrated in visible light, the malachite green acting as a photocatalyst for the reaction.’1 There can, however, be no doubt that the physiological factor—the reaction of the protoplasm with which the chlorophyll is associated in the chloroplast—plays a very important part in the process of photosynthesis. I hope to establish this in the present and succeeding chapters by showing that photosynthesis is modified by variations of external conditions just as are other modes of physiological response. The protoplasmic response to external change may be looked at as being the expression either of storage or of depletion of energy. The positive or anabolic response A is connected with the uphill work, increasing the potential 1 Heilbron, Nature, x\pril 14, 1923.