Drought stress significantly reduces grain yield (GY) due to poor spikelet fertility and anthesis quality. Aim of this study was to understand the changes of flowering capacity, anthesis quality traits and seed set in the re-watered drought stressed modern high yielding drought susceptible rice cultivar, IR64 at heading (DSH) and booting (DSB) stages. The well-watered plants served as control of the experiment. Results obtained suggest that spikelet moisture content at above 80% was required to maintain optimum anthesis process in rice. Anthesis process in DSH plant was suspended when leaf relative water content (LRWC) dropped to below than 70%. Effects of drought stress on the spikelet moisture were irreversible as compared to the leaf rolling and LRWC. Hence, seed set was failed to occur at the upper rachis branches of the DSH plant. Anthesis process in the re-watered drought stress plants was resumed on the third day after re-watering with about 50% and 80% of anthers managed to dehisce in the DSH and DSB plants. Consequently, percentage of spikelet fertility and seed set in the DSH and DSB plants were increased towards the lower parts of the panicle. The GY, number of seeds, spikelet fertility, and harvest index however were significantly lower in the DSH plant (0.30 g, 13, 16.40% and 14.81) as compared to DSB plant (1.34 g, 57, 59.14% and 48.30), respectively. In addition, all interrelated traits involved in the flowering process of rice could be collectively termed as the anthesis quality traits due to their significant correlation with the grain yield and other yield components.
Tekanan kemarau mengurangkan hasil bijian (GY) secara signifikan kerana tahap kesuburan spikelet dan kualiti pendebungaan yang rendah. Kajian ini bertujuan untuk memahami dinamika kapasiti pendebungaan, kualiti antesis dan pembentukan biji pada pokok padi yang diberi pengairan semula semasa tekanan kemarau pada dua fasa reproduktif iaitu semasa ‘heading’ (DSH) dan bunting (DSB). Pokok yang tidak diberi tekanan kemarau berfungsi sebagai eksperimen kawalan. Hasil kajian ini menunjukkan bahawa kadar kelembapan spikelet di atas 80% adalah diperlukan untuk proses pendebungaan yang optimum berlaku. Proses pendebungaan oleh pokok DSH terhenti apabila kadar kandungan air relatif daun (LRWC) lebih rendah daripada 70%. Kesan tekanan kemarau terhadap kadar kelembapan spikelet adalah tidak dapat dipulihkan berbanding dengan kadar penggulungan daun dan LRWC. Akibatnya, pembentukan biji padi tidak berlaku di bahagian atas panikel pokok DSH. Proses pendebungaan didapati berlaku pada hari ketiga selepas siraman dilakukan terhadap pokok DSH and DSB dengan kadar 50% dan 80% cepu debunga berjaya mengeluarkan debunga. Kesannya, peratusan kesuburan spikelet dan pembentukan biji oleh pokok DSH dan DSB meningkat pada bahagian bawah panikel. Walaubagaimanapun, GY, jumlah biji, tahap kesuburan spikelet, dan kadar indeks tuaian oleh pokok DSH jauh lebih rendah dan signifikan (0.30 g, 13, 16.40% dan 14.81) berbanding dengan pokok DSB (1.34 g, 57, 59.14% dan 48.30). Sebagai tambahan, semua ciri yang terlibat di dalam proses pendebungaan padi boleh disarankan untuk dinamakan secara kolektif sebagai ciri kualiti antesis kerana hubungan yang signifikan dengan GY dan komponen hasil lain.
Keywords: Reproductive Stage Drought; Spikelet Moisture Content; Yield and Its Components.
© Penerbit Universiti Sains Malaysia, 2022.