Volume 9, Issue 4
April 1939, pages 1-228
pp 1- April 1939 Erratum
pp 151-168 April 1939
The influence of fertilizers upon photosynthesis, chlorophyll content and respiration rate ofAndropogon sorghum (Var. Cawnpore 46) has been studied under ifferent combinations and levels of manuring.
When supplied singly potassic and phosphoric fertilizers are much more useful than the nitrogenous in increasing the photosynthetic efficiency of leaves. In all these cases photosynthesis rises with increasing supply of fertilizers upto a certain optimal level, later showing a decline.
In the three fertilizer series the rate of photosynthesis never reaches the same level as that recorded for optimal doses of potash and phosphates applied singly. The association of the three ingredients N2, P2O5 and K2O appears to slacken the rate of CO2 intake by leaves. When one or the other nutritive ingredient is either reduced or completely removed, this deleterious influence is partly overcome and photosynthesis increases.
The influence of fertilizers upon respiration, photosynthesis (both apparent and real) and chlorophyll is practically of the same nature, inasmuch as, augmentation in assimilatory activity in majority of cases is also followed by an increase in chlorophyll content and respiration rate.
Photosynthesis in different series of cultures does not rise with the increase in the chlorophyll content upto a critical limit of 2.0 mgm./fresh weight. Beyond this level, however, increase in chlorophyll is always associated with acceleration in photosynthetic activity.
The variation in assimilation number in different series of experiments indicates that chlorophyll is not the only factor controlling photosynthesis.
Photosynthetic augmentation under the influence of fertilizers may be due to (i) increased chlorophyll formation which in its turn influences carbohydrate metabolism, (ii) direct supply of mineral ingredients, nitrogen, phosphorus and potassium for proper functioning of leaf material and (iii) the increase in respiratory activity of leaves which considerably influences the rate of real assimilation.
pp 169-174 April 1939
The paper deals with the effects of injection of buffer solutions, varying in pH from 4.0 to 8.5, upon the photosynthesis and respiration of leaves ofSaccharum officinarum (Var. CO. 312).
A close relationship is found to exist between the photosynthetic and respiratory rates and the ‘final’ pH of buffers, although the reaction of the cell-sap is practically constant.
The high concentrations of the buffer solutions are, probably, responsible for depressing the rates below the values of the control, and for causing discoloured areas in the leaves in certain cases.
pp 175-223 April 1939
pp 224-228 April 1939