Anatomical characteristics of the upland local Indonesian rice cultivars as structural protection against drought

Drought-tolerant rice has various forms of adaptation responses, including root and leaf anatomical adaptations. In this study, we evaluated these anatomical adaptations by determining the anatomical characteristics of the roots and leaves of local Indonesian rice under drought conditions. This study aims to elucidate the basic anatomical features of leaves and roots that ensure drought tolerance in rice. Drought stress treatment was performed by using the fraction of transpirable soil water method with FTSW level 1 (control) and FTTSW 0.2 (severe drought). ‘Boawae 100 Malam’- BSM and ‘Situ Bagendit’- SB were used as the drought-tolerant cultivars, ‘Gogo Jak’- GJ was used as the moderate cultivar, and ‘Kisol’- KM and ‘Ciherang’-CH were used as the drought-susceptible cultivars. We utilized the freehand sectioning method for leaf anatomical tissue preparation and embedded tissues in paraffin for root anatomical preparation. We found that drought-tolerant cultivars underwent several anatomical changes, including reduced root diameter, stele diameter, xylem diameter, and cortex radius and thickened cells that supported improved water absorption under severe drought conditions. As a consequence of the structural adaptation of roots, several leaf characteristics for adaptation to drought were also found. These adaptations included the increased thickness of the mesophyll layer and lamina, enlarged and bulliform cells with increased stability, and broad vascular bundles composed of extremely thick tracheid and pit elements with small diameters.