| Inhibiting effects of peroxidase activity on dry matter
accumulation in developing kernels of bread wheat N.C. SHIGHAL, K.N. SRIVASTAVA and S.L. MEHTA Division of Genetics and Division of Biochemistry Indian Agricultural Research Institute New Delhi 11012, India In general, semidwarf wheats have low kernel weight in comparison to tall wheats (EPHRAT 1974). The possible reasons for the poor kernal weight in semi-dwarf wheats, include inadequate assimilation for filling of increased number of kernels, relatively higher respiratory losses or imgalanced activity of hormones during seed development. Our previous study (SINGHAL et al. 1979) had shown significant negative correlation between peroxidase activity in coleptile and kernel weight at maturity. The present study was planned to study the peroxidase activity in kernels during development and its relation with dry matter accumulation in kernels of wheat varieties. Materials and Methods Eight wheat genotypes differing in kernel weight and plant height were grown under high fertility condition (N.P.K. 100, 60, 40 kg/ha-1). The ears were harvested at 10, 17, 24, 31 days after anthesis and at maturity. The kernels were removed and stored in liquid nitrogen before enzyme assay or immediately analysed. All varieties except Mex C.B. 116 and Olesen's Dwarf took 37-40 days from anthesis to maturity. Mex C.B. 116 and Olesen's Dwarf matured in shorter time (33-35 days) from anthesis. Matured grain samples were taken at 40 days after anthesis in all the varieties. Dry weight of 100 kernels was determined by oven drying at 100C till constant weight. Fresh seeds were hand-ground in 0.05 M Tris-HCl buffer (pH 6.0, 1 : 5 W/V) with chilled pestle and mortar at 4C. The cell paste suspension was centrifuged at 10,000 x g for 15 min at 4C. The supernatant obtained was used for peroxidase assay. Peroxidase was assayed according to the method of SHANNON et al. (1966). The activity has been expressed as change in absorbance per min per g fresh weight. Results and Discussion Substantial variation was observed in the pattern of dry matter accumulation in developing kernels. Low kernel weight varieties like Kalyansona, Max C.B. 116 and Olesen's Dwarf accumulated upto 39.7 to 48.6 per cent of mature kernel weight till day 17 after anthesis while bold seeded varieties HD 1944, NP 880, Sonalika, K. 65 and Pusa 5-3 could accumulate only 21.9 to 38.1 per cent (Table 1). After day 24 all the bold seeded varieties accumulated greater dry matter than low kernel weight varieties. The triple dwarf variety HD 1944 was similar to double dwarf variety Kalyansona in its dry matter accumulation in kernels upto day 17 but later on HD 1944 accumulated more matter than Kalyansona. The variety Olesen's Dwarf had the highest peroxidase activity at all the stages of kernal development (Table 2). At maturity steep increase in peroxidase activity has been recorded in all the varieties. The correlation between peroxidase activity and kernel weight was highly significant negative at day 24, 31 and maturity (Table 3). At day 10 Sonalika and at day 17 Pusa 5-3 had accumulated the highest kernel weight and had the lowest peroxidase activity, while at the same time variety Olesen's Dwarf had accumulated the least kernel weight and showed the highest peroxidase activity. Pusa 5-3 from day 11 to 17 and NP 880 from day 18 to 31 accumulated higher kernel weight (1.28 and 4.20 g. respectively) and showed relatively lower peroxidase activity then others. The results, in general, indicate inhibiting effects of peroxidase towards the development of kernels. |
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