Biochemical and ecochemical assessment of healthy and declining Dalbergia sissoo plantation to recognize plant mortality reason
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Date
2018-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Dalbergia sissoo is widely distributed tree in tropical and sub tropical regions in general and is a significant component of the alley cropping system of agroforestry in particular. The tree is reported to have positive pharmacological and ethno-medicinal properties. Equivalently, there are a good number of reports indicating high mortality of the tree due to varied factors ranging from edaphic, pathological, silvicultural, entomological as well as certain soil factors. However, conclusive scientific studies are not sufficient in this regard. Keeping in mind the above-stated problem a lab experiment was conducted in 2017-2018 for biochemical and ecochemical assessment of healthy and declining Dalbergia sissoo plantation (four year old) and to recognize plant mortality reasons. From both healthy as well as declining tree, soil samples (at 5, 10 and 15 cm depth; from near as well as one meter away from the tree trunk) and leaf samples were evaluated for different physical (Soil pH, EC and NPK content) and biochemical properties (proline, chlorophyll, ascorbic acid, phenol, flavonoid antioxidant, enzyme activity etc.). Soil pH was significantly higher in case of declining and organic matter content was significantly higher in case of healthy tree at almost all the depths of sampling with minor variations while Soil EC didn’t differ significantly among the two types of trees. N content declined and K content increased in case of declining tree, while P content didn’t differ significantly for the two stages of trees. Total protein content in soil was observed to be significantly higher in healthy tree as compared to the declining one at all the depths. Amongst the soil enzymes tested, specific activity of protease and
beta glucosidase were observed to be marginally higher in case of healthy tree while urease activity was relatively greater in declining tree. Rhizospheric microbial activity at all sampling depths was significantly greater in case of healthy tree indicating good rhizosphere health in case
of healthy tree as compared to the declining tree. It followed from the results that primary stress/ageing indicators; proline content as well as membrane injury index value were expectedly
on a higher side in the declining tree while ascorbic acid, auxin and gibberellic acid i.e. growth promoters were observed to be greater in case of healthy tree. Concentration of micronutrients Fe, Ni and Zn was greater in case of declining trees. The result is in line with the fact that these micronutrients are the major cofactors of stress/ageing induced plant enzymes; the latter are upregulated in case of stress/ageing. In continuation with the above reasoning the amount of phenol, flavonoids and total antioxidants were observed to be significantly greater in case of declining tree. Total chlorophyll and total protein content in leaves were higher in case of green tree as compared to the declining one. The stress/ageing marker enzymes SOD (Superoxide dismutase), catalase and peroxidase were found significantly higher in case of the declining tree as compared to the healthy tree. An SDS-PAGE and GC-MS analysis of the samples from two types of trees indicated different but specific set of protein and metabolite fractions being active respectively, in healthy and declining trees.
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