Morphological and anatomical characteristics of Indonesian rice roots from East Nusa Tenggara contribute to drought tolerance

The ability of rice plants to cope with drought is supported by several parameters, including the structure of the root organ for water absorption. This study aimed to analyze the characteristics of the root tissues that play a role in supporting local rice plants during drought. This study was conducted by comparing 18 East Nusa Tenggara (Nusa Tenggara Timur [NTT]) local rice cultivars with two comparative drought-tolerant and drought-susceptible cultivars under drought stress treatment using the fraction of transpirable soil water method with levels 1 (control) and 0.2 (severe stress). Morphological measurement of plant growth and root phenotype, including root length and root dry weight, as well as plant height, number of leaves, and number of tillers, was conducted in the vegetative phase (46 days after planting). The collected root samples were prepared for anatomical slides using the paraffin embedding method and observed microscopically. Results showed the tendency of drought-tolerant plants to exhibit low reduction of the growth characteristics. In this study, drought tolerant rice cultivars (Pak Mutin, Boawae 100 Malam, and Kisol) tend to have root anatomical structure characterized by smaller root diameter, root area, cortical radius, vascular cylinder diameter, smaller cross-sectional of the vascular cylinder, and smaller metaxylem diameter with the higher number of metaxylem cells. In addition, thicker root epidermal cells and more schlerenchyma cell layers were also observed.