Screening of rice varieties with low accumulation of heavy metals based on leaf morphology

This study aimed to investigate the influence of the morphological traits of rice leaves (stomata, leaf area, and trichome density) on the accumulation of heavy metals in rice grains. It also screens for varieties with low heavy metal accumulation and high adaptability (less foliar uptake). Field trials on 37 rice varieties and pot trials regulated by abscisic acid (ABA) were conducted to explore the effects of various leaf surface morphologies and stomata on cadmium (Cd) accumulation in brown rice. Analyzing leaf morphology in different rice varieties revealed that five with high Cd content had an 8.92 %-38.49 % increase in stomatal pore area compared to the average. Meanwhile, these five rice varieties with high Cd content exhibited xylem Cd transit rates above average, ranging from 9.22 % to 182.58 %. Transporter factors throughout the rice plant indicated that the processes from stem-leaf to rachis and husk to brown rice are crucial for Cd accumulation in rice. The results of the correlation and structural equation modelling indicated a significant correlation between rice leaf stomata and the transit rate of Cd in rice xylem. ABA spraying experiments showed that stomata regulate rice transpiration and affect Cd transport and accumulation in rice. Results showed that ABA spraying significantly reduced Cd content in brown rice by 2.4 %-24 % and transpiration rate (33.17 %-54.45 %). Ultimately, the variety ZhuLiangYou 35, characterized by its smaller stomatal pore area and reduced heavy metal concentration in brown rice, is recommended as an appropriate choice.