Volume 32, Issue 6
December 1950, pages 231-288
pp 231-251 December 1950
In continuation of observations on the changes in ascorbic acid, dehydroascorbic acid and total ascorbic acid during germination of seeds, the day to day changes in the activities of ascorbic acid oxidase, glutathione, reducing sugars, free phosphates, nicotinic acid, amylase and phosphatase have been followed.
Germination in the dark has generally tended to enhance the various activities, except that of ascorbic acid oxidase. The probable bearing of these observations on the mechanism of ascorbic acid formation, has been discussed.
That enzymic and ionic copper oxidation of vitamin C are distinct is shown from studies with heated extracts of germinatedmung.
pp 252-268 December 1950
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.
pp 269-288 December 1950