. Botany for agricultural students. Plants. FACTORS INFLUENCING PHOTOSYNTHESIS 257 combining the elements of sugar, which is the foundational sub- stance, with nitrogen, sulphur, and phosphorus derived from the mineral salts of the soil. Even if the construction of proteins in leaves does not depend upon light, it is obvious that leaves are well equipped for such work, since they manufac- ture sugar and the water brought up from the soil supplies them with an abundance of mineral salts. Factors Influencing Photosynthesis. â The factors influencing photo- synthesis are light, temper- a t u r e,
. Botany for agricultural students. Plants. FACTORS INFLUENCING PHOTOSYNTHESIS 257 combining the elements of sugar, which is the foundational sub- stance, with nitrogen, sulphur, and phosphorus derived from the mineral salts of the soil. Even if the construction of proteins in leaves does not depend upon light, it is obvious that leaves are well equipped for such work, since they manufac- ture sugar and the water brought up from the soil supplies them with an abundance of mineral salts. Factors Influencing Photosynthesis. â The factors influencing photo- synthesis are light, temper- a t u r e, moisture, and amount of chlorophyll. That light is absolutely essential for photosynthesis is easily demonstrated by applying the iodine tests to two sets of leaves after one set has been kept in the dark and the other in the light for a few days. Even by shading only a portion of a leaf the necessity of light for photosynthesis can ^ig. 235. â A leaf showing the relation be demonstrated as shown f^ Photosyiithesis to light, as indicated by 17 u amount of starch formed. After cover- m Figure 23d. h or photo- i^g ^^g ^rea represented by the light band, synthesis sunlight is best, the leaf was left exposed to the sunlight for although some photosyn- a few hours, then removed from the plant thesis will take place in ^"^ *^e ^^^^^ ^^^^ applied. The area pro- ,n â 1 T 1, ,1 , 1 tected has no starch while the areas exposed artmcial light that has a .>. j i j ^ xi, r i . are qmte dark, due to the presence oi much suitable intensity. It has gt^rch. Adapted from Palladin. been demonstrated in greenhouses that some plants, at least, carry on photosynthesis at night if the proper kind of electric light is provided. For many plants the direct rays of the sun are too intense, in which case photosynthesis is most active in strong diffuse light. It is partly for this reason that Pineapples, Tobacco, Potatoes, Cotton,. Please note that these images are extracted from scanned page i
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