Practically nothing is certainly known of the details of the process of photosynthesis or of its first prliduet. Several theories have been pro posed; the most plausible is that of Bayer, which has reeently been receiving substantbil support, although it is by no means yet cleartv established. According to this theory the rearrangement of the elements of carbonic acid (lif '0,) results in the formation of formaldehyde (Clip) with the elimination of oxygen 1O,1. After time produc tion of formaldehyde it is condensed for 'polymer ized') into one of the simpler such as glucose IC„11,0„), which could he formed by the proper union of six molecules of formaldehyde. This again could be polymerized to form cane and cane sugar has been shown to he one of the early products of photosynthesis in a num ber of ordinary leaves. Starch, which is a very complex carbohydrate. must result from further compounding. and therefore eau be looked 11p0111 only as a still more remote produet. Some of the supports for Wiyer's hypothesis are as fol low,: First. green leaves and even uninjured seedlings have been supplied directly with gin eose, with the result that they nourish them selves therewith and store up reserve starch: sec ond. it has been possible to supply one of the products intermediate between formaldehyde and gluen,c, namely to 'starved plant. in the absence of CO,. with the result that they nourish themselves and store up starch; third, formaldehyde, though under ordinary con ditions a violent, poison, has been supplied at the moment of its formation to an alga and the plant nourished thereby; fourth. formaldehyde has re cently been detected in the green leaves of active plants: fifth, formaldehyde is produced from CO, in light in liquid containing leaf-enzymes and chlorophyll, though no living protoplasm be pres ent. Such experiments, while not conclusive_ strongly support the idea that formaldehyde is the first product of photosynthesis.
The by-product of photosynthesis, oxygen, is nearly equal in volume to that of the carbon dioxide absorbed. On the average it is a little less, lint in many experiments is at least S per cent. greater. In such cases the extra oxygen may lie derived from the decomposition of other in the plant, since it is impossible to distinguish all sources of the evolved oxygen.
Whirl] is always given off in the neutral (0,0.
IL is not possible to ascertain exactly the amount of carbohydrates made under given condi tions, since an indeti.rminate amount is used at once in the waking of other more complex pro teid foods, ant. other indeterminate ties are lost from any given region by migration. The net product has been determined in the sun flower as 1.0 to 1.8 grains of starch per hour per square meter: in the gourd. 1.5 to 1.7 grams; in the bramble. by a different method. 1.54 grams. The accumulation of the products of photosyn thesis never reaehes such a point in the normal plant that it interferes with the process. By artificial memos, however, this result may be brought about. Since the supply of energy to a well-illuminated plant is more than sufficient to enable it to utilize all the carbon dioxide which can enter the cells under the usual small partial pressure of emboli dioxide, increasing the pres sure of this in the atmosphere, and therefore sup plying, a greater quantity to the living tel increases the amount of carbohydrates produced. This increase is almost proportional to the rela tive increase of CO,. up to a point at which Otis gas retards other functions. -‘11 increase of Cf in the atmosphere from 3 parts in 10.000 to 000 or 800 parts proves beneficial for photosynthesis. Variations in other conditions, however, may so greatly affect this that ineonsistent results nmy Ile obtained from experiments.
The rate of photosynthesis is affected by time temperature, increasing with a rising temperature to an optimum, which is not far from the opti MIMI for growth. Vet it must be remembered that many plants flourish, and therefore may make food, at very low temperatures, e.g. the Age in Arctic waters, or at very high tempera tures, e.g. algae in hot springs. In conifers, photosynthesis has been reported as occurring at temperatures even below 0' C. Though the leaves and surface tissues of plants are especially liable to lose water, and therefore to become flac cid, no interference with photosynthesis results.