The Effect Of Sees Priming On Germination, Growth Performance And Yield Of Dry Direct-seeded Rice

The dry direct-seeded rice technology has been proposed to increase resource use efficiency, save labor demand, and be easy to mechanization, which is one of the the preferred options for stabilizing rice planting area and improving rice production during the transition period of rice cultivation technology. However, poor stand establishment under drought stress is the major constraint to the wide adoption of dry direct-seeded rice. Many previous studies reported that seed priming is one of the most effective, pragmatic and short-term approaches for increasing seed vigor, synchronization of germination, as well as the seedlings growth of many crops under different abiotic stress including drought. Despite the availability of volumetric information on rice seed invigoration techniques, priming agents like spermidine(Spd), polyethelene glycol-6000(PEG), potassium nitrate(KNO3) have rarely been tried in dry direct-seeded rice under drought stress.The aims of this study are:(1) to determine the appropriate priming agent and their concentrations under drought stress in dry direct-seeded rice;(2) to examine the changes in biochemical attributes of rice seedlings induced by seed priming under drought stress;(3) to observe the effects of seed priming treatment under different soil moisture conditions and identify the minimum threshold of soil water content under which primed seeds can germination;(4) to examine the effect of seed priming treatment on seed germination, the performance of seedling, yield and yield component in an open-field experiment under dry direct-seeded rice system. The results obtained are as followed:(1)Seed priming treatments were effective in improving seed germination and early seedling growth of eight cultivars. The responses of seeds germination potential and seedling growth performance to priming agents were different, the effects of KNO3, PEG, Spd priming was better than that of water priming. The study also indicated that the preferred priming treatments were 0.5% KNO3, 10% PEG, 0.5 mmol L-1 Spd based on germination and early seedling growth.(2)The seed priming can alleviate the negative effects of drought stress on emergence as well as seedling estabilishment and growth of dry direct-seeded rice. Furthermore, better germination and vigorous seedling growth due to seed priming was associated with increased α-amylase activity, promoted the degradation of starch, speeded up the process of glucose metabolism, increased soluble content, but also reduced the MDA content and increased the activity of antioxidant enzymes in seedlings, which promoted seed germination and seedling growth.(3)The differences in responses of seeds germination and seedlings growth performance to seed priming treatments were observed between Huanghuazhan(HHZ) and Yangliangyou6(YLY6). For HHZ, the best growth performance was found in 0.5 mmol L-1 Spd, while in 10% PEG for YLY6.(4) Within certain range, the promoting effects of seed priming on germination and seedlings growth performance showed an increasing trend with reducing soil water content, the growth advantage of primed seedlings mainly performed in maximum root length or root fresh weight per seedling. The minimum threshold of soil water content under which primed seeds can germinate is about 8%.(5) Results of open-field experiment showed that priming treatments significantly improved the ability of early vigorin dry direct-seeded rice system. Furthermore, priming treatment significantly increased yield, which was attributed to increases in panicles m-2 or spikelets m-2. Therefor, seed priming technology is expected to become an effective way to resolve poor stand estabilishment of dry direct-seeded rice.