SEED TREATMENT WITH PACLOBUTRAZOL AFFECTS EARLY GROWTH, PHOTOSYNTHESIS, CHLOROPHYLL FLUORESCENCE AND PHYSIOLOGY OF RICE

Abstract

A pot experiment was conducted to investigate the effects of paclobutrazol seed treatment on early growth, photosynthesis and physio-biochemical attributes on rice. The seeds of two rice cultivars i.e., Basmati-385 and Xiangyaxiangzhan were treated with paclobutrazol at 40 mg per 5 kg of seeds (T) whilst non-treated seeds were taken as control (CK). Result showed that the seedling length of Basmati-385 and Xiangyaxiangzhan was reduced by 32.16 and 26.85% when seeds were treated with paclobutrazol, however, net photosynthetic rate, maximal efficiency of PSII photochemistry (Fv/Fm) and electron transport rate (ETR) were increased by 25.34 and 7.98%, 4.22 and 7.76% and 30.07 and 11.84% in Basmati-385 and Xiangyaxiangzhan, respectively. The malondialdehyde (MDA) contents were reduced up to 14% in both rice cultivars under paclobutrazol treatment. Furthermore, the activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) were increased by 4.92 and 3.58%, 10.64 and 14.42%, 31.19 and 25.80% in paclobutrazol treated seeds than CK in both Basmati-385 and Xiangyaxiangzhan, respectively. In addition, dry weight per unit seedling length was significantly correlated with SPAD values, root length, surface area, diameter, and root volume, net photosynthetic rate, chlorophyll a, chlorophyll b, carotenoids, Fv/Fm, ETR, antioxidant enzymes, soluble sugar, and soluble protein of both rice cultivars. However, negative correlations were also recorded between dry weight per unit seedling length and intercellular CO2, transpirational rates, non-photochemical quenching (NPQ) and malondialdehyde (MDA) contents in both Basmati-385 and Xiangyaxiangzhan. Hence, paclobuztrazol seed treatment enhanced photosynthetic and gas exchange attributes, physio-biochemical attributes and root morphological characters in rice.