EFFECTS OF BLUE LIGHT AND PACLOBUTRAZOL ON SEED GERMINATION, VEGETATIVE GROWTH AND YIELD OF BLACK RICE (Oryza sativa L. ‘Cempo Ireng’)

Abstrak

Black rice (Oryza sativa L. “Cempo Ireng”) is one of the local rice varieties in Sleman Regency, Yogyakarta. Its black color is caused by a high anthocyanin content, which is an important source of antioxidants. The cultivation of black rice is still limited due to its tall phenotype, long vegetative stage, and lower productivity compared to white rice. Paclobutrazol is a growth retardant that causes dwarfing in several crop plants and reduces lodging. Blue light can improve plant quality. This research aimed to evaluate the effects of blue light and paclobutrazol on seed germination, vegetative growth, and yield of black rice. The results showed that the average seed germination and the α-amylase activity of seeds exposed to blue light were lower compared to those exposed to sunlight; however, paclobutrazol concentrations did not affect the seed germination percentage. The height of rice plants treated with paclobutrazol decreased in accordance with increasing paclobutrazol concentration. Chlorophyll content and tiller numbers increased with 12.5 ppm paclobutrazol treatment. Nitrate reductase activity was higher in rice seedlings subjected to blue light compared to sunlight. Iron (Fe) content in rice plants treated with 25 or 50 ppm paclobutrazol increased compared to the control. In conclusion, paclobutrazol application at 12.5 ppm effectively reduced plant height, and higher concentrations caused greater height reduction. Blue light treatment during black rice seed germination slightly reduced germination percentage and α-amylase activity. However, when combined with paclobutrazol application, blue light treatment increased chlorophyll content, tiller numbers, and Fe content in black rice grains.