Products of Photosynthesis

The products of photosynthesis are the carbohydrates and oxygen. Four carbohydrates, D-glucose. D-fructose, sucrose and starch are commonly are formed in the green cells during photosynthesis. Plant physiologists and biochemists have tried to find the first product of this process. But still it is not clear which the first product of photosynthesis. There are following products of photosynthesis:

I. Hexoses: According Weevers the first Carbohydrates were the

hexoses. After that sucrose and later starch appeared. Thus the carbohydrates appeared in the order of their complexity. The sucrose and starch are formed from hexoses by following equation.

C6H1206 + C6F11206 ___________ • C121122011 +020

Glucose        + Fructose                            Sucrose

(Cal I 206)n + 920 __________ n ( Call 1206L

Starch


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  1. Sugar phosphate: Calvin used carbon dioxide containing radioactive carbon (C”). He found that the first carbohydrate produced in photosynthesis was sugar phosphate. The first free sugar was sucrose. Glucose and fructose appeared later on. Thus it is not essential for free hexoses to accumulate before sucrose arid starch are formed. Thus the phoskhorylated sugars are the precursors of these substances.
  2. Amino acids: The products other than carbohydrates like amino acids and related compounds may be formed as result of photosynthesis.
  3. Starch: Starch is accumulated in the chloroplasts of most species after photosynthesis. Starch is not the first product of photosynthesis. It is the product of a secondary reaction called starch synthesis. It is formed by the condensation of sugar. The rate of starch synthesis depends upon on the rate of photosynthesis. Starch synthesis is an entirely independent process from photosynthesis. It starts after the process of photosynthesis. It can proceed only when sugar is present in the cells. Leaves of many species do not form starch. Yet photosynthesis takes place in them. Starch synthesis also takes place in the non-green cells of the stem.
  4. Oxygen: It is a by-product of photosynthesis. It has great significance in nature. It is the most important means of returning oxygen to the atmosphere. The ratio of the volume of oxygen evolved to the volume of carbon dioxide taken in photosynthesis is called the photosynthetic ratio or photosynthetic quotient. Willstatter and Stoll found that the value of this ratio is unity.
  5. Products of Photosynthesis

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