. Botany for agricultural students. Plants. FACTORS INFLUENCING PHOTOSYNTHESIS 259 combustion, and all oxidation processes in maintaining the supply of carbon dioxide for photosynthesis. Roughly estimated, 150 square meters of leaf area will use up in one summer all of the carbon dioxide which an average man produces through respira- tion in one year. When one considers that the amount of carbon dioxide in the air is only about per cent, that is, about 3 parts in 10,000 parts of air, it is surpris- ing that plants can make sugar as rapidly as they do. Sometimes, as around cities with many
. Botany for agricultural students. Plants. FACTORS INFLUENCING PHOTOSYNTHESIS 259 combustion, and all oxidation processes in maintaining the supply of carbon dioxide for photosynthesis. Roughly estimated, 150 square meters of leaf area will use up in one summer all of the carbon dioxide which an average man produces through respira- tion in one year. When one considers that the amount of carbon dioxide in the air is only about per cent, that is, about 3 parts in 10,000 parts of air, it is surpris- ing that plants can make sugar as rapidly as they do. Sometimes, as around cities with many factories, the per cent of carbon dioxide may be a little higher but it is always exceedingly low. Of course carbon dioxide is present in solution in the soil water; but it is easily demonstrated that this carbon dioxide is of practically no help to plants in photosynthesis. To compensate for the limited amount of carbon dioxide, it is obvious that leaves need broad surfaces and a thorough distribution of chlorophyll, so that their 'absorbing surface may be large. However, with all of these adjust- ments of the plant, it has been demonstrated -p ^ ^ 2 3 6 — L f that the normal supply of carbon dioxide showing the effect on is often insufficient for the maximum photosynthesis of clos- amount of photosynthesis; for some plants, ing the stomata. The when surrounded by air in which the stomata on the under , e 1 1 • • 1 • • 1 surface of the white area amount oi carbon dioxide is increased up i . u ^ were closed by covering to 1 per cent, show a corresponding rise in the epidermis with vase- photosynthetic activity. hue, thus fiUing the Since stomata are the openings through stomata and excluding which carbon dioxide enters the leaf, their ^^^^o" dioxide. After number per area of leaf surface and the extent to which they are open affect the amount of this gas that reaches the mesophyll. That photosynthesis is inhibited when stomata are closed is demonstrated by the e
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectplants, bookyear1919
