Seed invigoration with inorganic nanoparticles in chillies (Capsicum annuum l.)

Abstract

A study entitled ‘Seed invigoration with inorganic nanoparticles in chillies (Capsicum annuum L.)’ was conducted in the Department of Seed Science and Technology, College of Horticulture, Vellanikkara between February 2018 and May 2019 to investigate the effect of nano and bulk particles of zinc oxide (ZnO) and titanium dioxide (TiO2), on longevity of chilli variety Anugraha. The present study was subdivided into four experiments. In experiment I, fresh seeds of chilli were treated with ZnO (nano and bulk particle) and stored under ambient conditions. Experiment I consisted of dry dressing chilli seeds with TiO2(nano and bulk). In both the experiments treated seeds performed better than the control. In experiment I, the seeds treated with T3 - ZnO @ 900 mgkg-1, T4 - ZnO @ 1300 mgkg-1, T6 - nano ZnO @ 250 mgkg-1 and T7 - nano ZnO @ 500 mgkg-1 were able to maintain the minimum germination standard of 60.00 per cent stipulated by the IMSCS (Indian Minimum Seed Certification Standards) in chilli upto 10 MAS. The vigour index-I and II were found to be high in T4 (ZnO @ 1300 mgkg-1), T7 (nZnO @ 500 mgkg-1) and T3 (ZnO @ 900 mgkg-1). The seed leachate obtained from T7 gave the lowest measurement (246 μS cm-1) of electrical conductivity. Control seeds were found to contain higher per cent of infection on comparison with the treated seeds. Chilli seeds treated with T3 - TiO2 @ 900 mgkg-1, T4 - TiO2 @ 1300 mgkg-1, T6 - nanoTiO2 @ 250 mgkg-1 and T7 - nanoTiO2 @ 500 mgkg-1 were able to maintain IMSCS up to ten months of storage, while the control (T1) lost the germination after eight months, i.e., T7 (63.00 per cent), T3 (61.33 per cent), T4 (61.00 per cent) and T6 (60.00 per cent). At the end of ten months of storage, all the treated seeds had lower electrical conductivity compared to control seeds. In both experiments, the seed infection per cent was found to be higher in untreated seeds compared to the treated ones. It was also evident that the treated seeds possessed better seed quality parameters compared to untreated seeds (control). In experiments III and IV fresh seeds which were treated with various doses of zinc oxide and titanium dioxide respectively, were subjected to accelerated ageing at a temperature of 40±1°C and relative humidity of 100 per cent for one day. In experiment III, the zinc oxide treated seeds after accelerated ageing revealed that seeds treated with T7 - nano ZnO @ 500 mgkg-1 retained a high germination of 49.00 per cent, followed by T4 (43.00 per cent). In terms of vigour index I and II, T7 and T4 were found to be on par with each other. The seed infection was found to be lower in nano ZnO treated seeds compared to control and normal grade ZnO treated seeds. The least infection was detected in T7 - nano ZnO @ 500 mgkg-1. Experiment IV consisted of untreated and TiO2 treated seeds which were subjected to accelerated ageing. Even after artificial ageing, T7 - nano TiO2 @ 500 mgkg-1 was able to retain 51.67 per cent germination in the first month. It was on par with T4 - TiO2 @ 1300 mgkg-1 (47.33 per cent) and T3 - TiO2 @ 900 mgkg-1 (44.67 per cent). The highest vigour index was observed in seeds treated with T7 - nano TiO2 @ 500 mgkg-1 (520) and it was on par with T4 - TiO2 @ 1300 mgkg-1 (437). T7 exhibited the highest vigour index-II (953) and was on par with T3 - TiO2 @ 900 mgkg-1 (863) and T4 - TiO2 @ 1300 mgkg-1 (813). The lowest electrical conductivity was obtained from the seed leachate of T7 (246 μS cm-1). The seed infection per cent was found to be the least in T7 - nano TiO2 @ 500 mgkg-1 treated seeds. Scanning electron micrograph of the radicles of seeds treated with nZnO and nTiO2 @ 500 mgkg-1 revealed higher cell proliferation at root tip and larger cells in the zone of elongation. The results obtained indicate that dry dressing of chilli seeds with zinc oxide and titanium dioxide is effective in improving the seed quality parameters during storage. The results of accelerated ageing test are also in agreement with the results obtained from storage under ambient conditions during natural ageing. Among various doses of zinc oxide T7 - nano ZnO @ 500 mgkg-1 and T4 - ZnO @ 1300 mgkg-1 exhibited the best results, whereas, among titanium dioxide treatments, T7 - nano TiO2 @ 500 mgkg-1 and T4 - TiO2 @ 1300 mgkg-1 seed were found to be the best doses.