Effect of zinc on nitrogen metabolism and nutritive value of clusterbean (Cyamopsis tetragonoloba (L.) Taub.)
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Date
2008
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Publisher
CCSHAU
Abstract
The present investigation was designed to evaluate the effect of zinc
through soil and foliar spray of 0.5 per cent ZnSO4 on clusterbean. Clusterbean
(Cyamopsis tetragonoloba (L.) Taub. Cv. HG563) plants were raised in earthenware
pots filled with zinc deficient sandy loam soil and treated with 0.0, 2.5, 5.0 and 10.0
ppm zinc in soil in first experiment where as in second experiment plants were
sprayed with 0.5 per cent ZnSO4 at 25, 45 and 25 as well as 45 DAS.
Zinc deficiency symptoms appear in control plants after 15 days of
sowing as smaller terminal leaves, discoloration between veins, stunted plant growth
with reduced leaf number and plant height which was corrected after application of
zinc. All morphophysiological parameters increased with zinc application through soil
and foliar spray. In general, all the morphophysiological parameters increased with
advancement of growth attaining maximum value either at 50 DAS (flowering stage)
and declined at 70 DAS (grain filling stage) or increased up to maturity. Pod yield and
seed yield on per plant basis was increased in zinc treated plants (by 1.4 fold in
ppm zinc treated plants) as compared to control. The magnitude of increase in the
morphophysiological parameters are correlated well with the amount of zinc in various
plant parts, which was increased with zinc application in both the experiments. This
in turn resulted in significant increment in total chlorophyll and chlorophyll ‘a’
content in leaves and thus might increase the rate of photosynthesis. Both soil as well
as foliar application of Zn+2 enhanced the activity of key enzymes of nitrogen
metabolism viz. nitrogenase, nitrate reductase, nitrite reductase, glutamine
synthetase and glutamate dehydrogenase on per plant as well as per mg protein basis.
The above increase in the efficiency of nitrogen metabolism results into increased
protein content in leaves, shoots, pods and seeds. Gum content was also enhanced in
seed at maturity upon the soil application of 2.5, 5.0 and 10.0 ppm Zn+2 and foliar
spray of 0.5 per cent ZnSO4. Zinc application also significantly improved the nutritive
value of leaves, shoots and pods, by decreasing NDF, ADF, cellulose and lignin
content, which resulted into increase in in vitro dry matter digestibility. Hemicellulose
and silica content did not follow regular trend with zinc application.
Zinc either through soil or foliar application of Zn+2 have both
synergistic and antagonistic effects on the Fe, Cu and Mn content. Iron and copper
content synergistically increased at lower Zinc dose and decreased at higher doses.
Whereas, Mn content was antagonistically related to increased zinc. Application of
zinc through soil was more beneficial then through foliar spray. Zinc application
through soil and foliar spray ultimately resulted into increase in fodder and seed yield.
Description
Keywords
Planting, Zinc, Enzymes, Biological development, Drying, Inorganic acid salts, Root nodulation, Wells, Sowing, Vegetative propagation