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Central Agricultural University, Pasighat

The Central Agricultural University has been established by an act of Parliament, the Central Agricultural University Act, 1992 (No.40 of 1992). The Act came into effect on 26th January, 1993 with the issue of notification by the Department of Agricultural Research and Education (DARE), Govt. of India. The University became functional with the joining of first Vice-Chancellor on 13th September, 1993. The jurisdiction of the University extends to six North-Eastern Hill States viz., Arunachal Pradesh, Manipur, Meghalaya, Mizoram, Sikkim and Tripura, with headquarters at Imphal in Manipur. College of Horticulture & Forestry, a constituent College of the Central Agricultural University, Imphal, Manipur, was established on 7th March 2001 at Pasighat, Arunachal Pradesh on the bank of beautiful river Siang.

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Author: Khongla, Lakidon × End date: 2019 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Response of different Citrus species of Arunachal Pradesh against Aluminum and Manganese Toxicity
    (College of Horticulture and Forestry, Central Agricultural University, Pasighat, 2019-07-01) Khongla, Lakidon; Wangchu, L.; Hazarika, B.N.
    The effects of Aluminium and Manganese toxicity, applied singly or in combination, on the growth, photosynthetic attributes, oxidative stress and anti-oxidative capacities of 5 citrus species were evaluated in this study. This experiment was taken up to understand the tolerance mechanism of citrus to the toxicities which occur in acid soils and to identify species better suited for such soils. In this experiment, Rough lemon (Citrus jambhiri), Rangpur lime (Citrus limon), Indian wild orange (Citrus indica) and two local citrus species viz., Tasi and Samphola were evaluated for a period of 20, 40 and 60 days in a sand culture experiment wherein 3 doses of Mn (0, 300 µM, 600 µM) and 4 doses of Al (0, 600 µM, 1200 µM, 1800 µM) were incorporated, either singly or in combination, to their nutrient solutions. Here, morpho-physiological parameters indicate a significant negative impact of the treatments on all the citrus species with growth inhibition by Mn treatments more pronounced in shoots while Al affected root growth more than shoot. Chlorophyll content and total soluble protein also declined with the increase in treatment concentration and exposure time although the least decline was observed in Samphola followed by Rough lemon. The peroxidation of lipids and the accumulation of reactive oxygen species (ROS) viz., superoxide anion (O2•-), hydroxyl free radical (-OH) and hydrogen peroxide (H2O2) revealed that Tasi followed by Rangpur lime was the most sensitive as both species recorded high amounts of ROS when compared with other species indicating that they may show lower resistance to the stresses induced. Al content in citrus shoots and roots also elevated with the increase in their concentrations and exposure time. Mn content also increased in both shoots and roots, however, addition of Al (600 µM) resulted in lower Mn accumulation (300 µM) than compared to the same treatment applied singly and this reduction was also reflected in lowered negative impact of physical parameters, particularly, shoot length, shoot weight (fresh and dry), relative water content and other parameters including lipid peroxidation and ROS accumulation. Antioxidants, both enzymatic and non-enzymatic, showed heightened activities in all the citrus species with the increase in time exposure although non-ezymatic antioxidants (ascorbic acid and tocopherol) progressively declined with time. The comparatively low antioxidant capacity of Tasi and Rangpur lime reflects their low resistance as evident from their high ROS production as well as more severe decline in their physical growth. Therefore, on considering the tolerance levels of the citrus species by their antioxidative defense, this experiment revealed that Samphola, followed by Rough lemon and Indian wild orange exhibited better tolerances to both Mn and Al toxicity while Tasi and Rangpur lime exhibited comparatively lower resistance to these stresses. It can also be concluded that antagonistic relationship is observed between Al and Mn although the effect is dose responsive as it is seen only in the lowest doses of both Al and Mn.