K N Lal
Articles written in Proceedings – Section B
Volume 8 Issue 4 October 1938 pp 301-308
An attempt has been made in this paper to study the photosynthetic activity of a number of plant species under optimum yet identical conditions of factor-intensity and to trace the relationship, if any, between the organic materials subsequently formed and the assimilatory influx of carbon dioxide.
Different plant species have different photosynthetic rates, the range of variation from species to species becoming more and more pronounced with advance in age of plants. Such variations under otherwise constant external conditions are discussed with special reference to internal factors.
The water-content of the experimental material no doubt differs from plant to plant but does not follow the same gradation as that maintained by assimilation rate. The chlorophyll content too shows no correlation with the assimilatory efficiency.
There seems to be a fair degree of correlation between the products economised in leaves during their photosynthetic activity and the products stored by the same species towards the close of the life-cycle. Plants economising sugars, proteins, starches and fats in assimilating leaves also store such substances respectively in their storage organs towards the close of their life-cycle.
The photosynthetic rate seems to be related to the nature of the end products accumulating in assimilating leaves. Leaves accumulating simpler sugars have fairly high rates of assimilation while those economising the more complex starches, proteins and fats respectively have to their credit decreasing assimilatory efficiency.
The biochemic constitution of the experimental material as judged by the products economised during assimilation appears to be an important internal factor governing photosynthesis and suggestively explains the phenomenon of photosynthetic specificity in certain groups of crop plants.
Volume 9 Issue 4 April 1939 pp 151-168
The influence of fertilizers upon photosynthesis, chlorophyll content and respiration rate of
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.
Volume 24 Issue 5 November 1946 pp 225-242
Volume 29 Issue 3 March 1949 pp 109-128
Volume 32 Issue 5 November 1950 pp 179-204
Volume 32 Issue 6 December 1950 pp 252-268
This paper elucidates the interrelation between leaf area and other leaf characteristics in six varieties of sugarcane grown under field conditions. Relation between these features and drought resistance in sugarcane is also analysed.
Drought-resistant behaviour of Rheora is associated with poor leaf surface and small size of leaves. Co 205 approaches this variety most in the characteristics of its leafy growth.
Leaf surface expansion is found to be determined by three conditions, namely, increase in (i) leaf length, (ii) leaf width and (iii) dry weight of leaves. High positive correlation between these factors and leaf area indicates that these characteristics are highly correlated. The possibilities of water content showing negative correlation with leaf area is also pointed out.
Relation between leaf area and linear measurements of length and breadth is expressed by the following two equations: For a single leaf:— Log A = Log L + Log B + Log K (1) For a population of leaves:— Log Σ A = Log Σ L + Log ΣB + Log K - Log N, (2) where A is leaf area, L = leaf length, B is leaf breadth, K is leaf factor and N is number of leaves.
The leaf factor K appears to be an important physiological constant representing the relation between linear growth (L x B) and leaf area. Its relatively low value in drought-resistant Rheora and also in Co 205, as against its relatively high value in other varieties with high leaf indices— Co 290, Co 453, Co 385 and Co 312—is characteristic.
Volume 33 Issue 1 January 1951 pp 1-13
The paper narrates the results of an experimental enquiry on respiration rate of sugarcane leaves of different stages of development under four conditions of nutrition,
Co 205 and Rheora show high leaf respiration as compared with Co 453 and POJ 2878, having significantly lower respiration rates. No differences in leaf respiration upto the third or fourth leaf stage are noted; beyond this the greater the stage of leaf development, the lower is the respiration of leaves.
Nutritional conditions bring about considerable changes in respiration of leaves. Thus nitrogen deficiency shows normal leaf respiration at maturity as compared with either phosphorus or potassium deficiency, each of which exhibit supernormality in respiration.
Variations in respiration rate under these conditions appear to be determined by changes in chemical composition of leaves, particularly nitrogen and carbohydrate fractions. Observed differences in respiration are discussed in the light of such changes.
Volume 33 Issue 2 February 1951 pp 69-91
Volume 42 Issue 6 December 1955 pp 258-282