Evaluation of growth and physiological characters of local rice under drought conditions

Global warming has increased the frequency of drought events, posing a significant threat to rice production and potentially reducing yields by up to 60%. Drought stress disrupts key physiological processes in rice, particularly carbon fixation, due to stomatal closure. Local rice varieties represent valuable germplasm resources for developing drought-resistant cultivars. This study aimed to evaluate the growth and physiological responses of several local Central Java rice varieties under varying levels of drought stress. This research used a split-plot design with four levels of field capacity (FC) (100%, 75%, 50%, and 25%) as the main plots and seven rice varieties (Ciherang, IR64, Hitam Cempo, Hitam Mutiara, Merah Sengreng, Putih Mentikwangi Karanganyar, and Putih Mutiara) as the sub-plots. Drought stress was applied during the vegetative phase. The observed parameters included agro-morphological traits (plant height, number of tillers, and number of leaves) and physiological traits (relative water content/RWC, photosynthetic rate, stomatal conductance, water use efficiency/WUE, and chlorophyll content). The results indicated that drought stress generally reduced plant height, tiller number, and leaf number in most varieties. Hitam Mutiara exhibited the largest decline in tiller and leaf number, whereas IR64 experienced the smallest reduction. However, the physiological responses varied greatly. Under severe stress conditions (25% FC), local varieties such as Putih Mutiara, Putih Mentik Wangi Karanganyar, and Hitam Cempo demonstrated superior adaptation mechanisms, characterized by increased RWC, photosynthetic rates, and WUE. Conversely, the IR64 variety showed high sensitivity to drought, exhibiting the lowest WUE under stress. Several varieties also increased their total chlorophyll content as a defense mechanism. In conclusion, the local rice varieties Putih Mutiara, Putih Mentik Wangi Karanganyar, and Hitam Cempo demonstrated stronger physiological adaptation mechanisms to drought stress compared to the control varieties. These varieties hold strong potential as genetic resources for the development of drought-tolerant rice cultivars.