North Eastern Hill University

About: North Eastern Hill University is a education organization based out in Shillong, Meghalaya, India. It is known for research contribution in the topics: Population & Catalysis. The organization has 2318 authors who have published 4476 publications receiving 48894 citations.

Effect of surface modes on the six-dimensional molecule-surface scattering dynamics of H2-Cu(100) and D2-Cu(111) systems.

Abstract: We include the phonon modes originating from the three layers of Cu(100)/Cu(111) surface atoms on the dynamics of molecular [H2(v,j)/D2(v,j)] degrees of freedom (DOFs) through a mean field approach, where the surface temperature is incorporated into the effective Hamiltonian (potential) either by considering Boltzmann probability (BP) or by including the Bose–Einstein probability (BEP) factor for the initial state distribution of the surface modes. The formulation of effective potential has been carried out by invoking the expression of transition probabilities for phonon modes known from the “stochastic” treatment of linearly forced harmonic oscillator (LFHO). We perform four-dimensional (4D⊗2D) as well as six-dimensional (6D) quantum dynamics on a parametrically time and temperature-dependent effective Hamiltonian to calculate elastic/inelastic scattering cross-section of the scattered molecule for the H2(v,j)–Cu(100) system, and dissociative chemisorption–physisorption for both H2(v,j)–Cu(100) and D2(v...

Seed dormancy, germination and seedling characteristics of Elaeocarpus prunifolius Wall. ex Müll. Berol.: a threatened tree species of north-eastern India

Abstract: Elaeocarpus prunifolius Wall. ex Mull. Berol. is a threatened tree species of north-eastern India. The present study was undertaken to investigate the type of dormancy prevailing in seeds of E. prunifolius, explore seed dormancy breaking techniques and assess seedling fitness. Ripe fruits of E. prunifolius were harvested from Jaintia hills, and seeds were subjected to various physical, manual and chemical treatments. The effect of plant growth regulators, viz gibberellic acid (GA3) and potassium nitrate (KNO3), were tested. Seedling vigour and survival based on seed weight were examined. Germination took 6 months to initiate after seed dispersal and natural germination percentage of fresh seeds was 24%. Physical pre-germination treatments such as surface and acid scarification failed to overcome dormancy. Cracked seeds promoted germination (46%) with a mean germination time of 146 days (time to 50% germination, T50 = 144 days). Among the GA3 treatments, split seeds treated with GA3 (3000 mg/L−1) yielded the highest germination (24%) with a T50 of 55 days whereas KNO3 did not promote germination. A combination of GA3 and KNO3, however, increased the germination to 31%. Between the seed weight classes, the highest percentage of germination was observed in heavy seeds (25%) and the lowest in light seeds (20%). There was no significant variation between seed weight and germination time (p > 0.05). Seed weight had a significant effect on the shoot height, number of leaves and dry weight of seedlings (p < 0.05). Based on the seed tests, E. prunifolius seeds exhibits ‘combined’ dormancy (physical and physiological) as splitting seed coat and application of GA3 effectively broke dormancy. Splitting the seed coat is a cost-effective method for accelerating germination of seeds. Heavy-weight seeds produced better performing seedlings compared to their counterparts which may be viewed as an important reproductive strategy of the species.

Insights into nuclear DNA content, hydrogen peroxide and antioxidative enzyme activities during transverse thin cell layer organogenesis and ex vitro acclimatization of Malaxis wallichii, a threatened medicinal orchid.

Abstract: Malaxis wallichii (Lindl.) Deb, a small, perennial, monopodial, terrestrial orchid, is endemic to tropical Himalayas at an altitude of 1200–2000 m asl. The pseudobulbs are important ingredients of century old drug ‘Ashtavarga’ and a polyherbal energetic tonic ‘Chyavanprash’. An efficient genetically stable in vitro propagation protocol using transverse thin cell layer culture system was established for M. wallichii. In the present report, meta-topolin alone proved to be three times more beneficial compared to other routinely used cytokinins in inducing highest number of shoot buds, plant height and growth of regenerated shoots. The highest regeneration frequency (89%) along with maximum number of adventitious shoots per explant (22.5 ± 0.6) was observed in MS medium supplemented with 1.0 mg/l meta-topolin and 0.5 mg/l α-naphthalene acetic acid. Highest rooting frequency with highest number of roots (8.66 ± 0.3) was achieved in half-strength MS medium fortified with 1.0 mg/l indole acetic acid. Clonal stability of in vitro-derived plantlets was evaluated and compared to donor plant using intron splice junction (ISJ) markers and flow cytometry. ISJ markers revealed 4.76% clonal variability indicating high degree of genetic stability amongst the in vitro-derived regenerants. The nuclear DNA content of M. wallichii (2n) was found to be 2C = 2.760 ± 0.02 pg and therefore, 1349.64 Mbp (1C). Flow cytometry analysis of actively growing young and mature leaves from donor as well as in vitro-derived plantlets revealed presence of three peaks corresponding to 2C, 4C and 8C, while 2C was the most abundant. In the present investigation, there was no significant difference in the 2C DNA content between the mother and in vitro-derived plants; however, the frequency of endopolyploid cells varied in young and adult plants. An increased H2O2 content as well as lipid peroxidation activities were observed during early stages of acclimatization which declined afterwards. The enhanced activities of antioxidant enzymes like superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase in acclimatized plantlets as compared to in vitro-grown ones revealed their active involvement in growth and development against oxidative stress under external adverse environment.