Selected Physiological Traits of Hevea brasiliensis Clonal Seedlings Influenced by Water Stress

Abstract

Water stress has been identified as one of the most critical environmental factors that will affect crop productivity in the coming years. Since the propagation of Hevea brasiliensis uses the bud-grafting method, selecting a good rootstock is crucial to withstand water stress conditions. This is due to the rootstock scion interaction accounting for about 20% contribution to the scion growth. In this study, four Hevea clonal seedlings namely RRIM 2002, RRIM 2020, RRIM 2023 and RRIM 2024, were observed for their intrinsic tolerance to water stress conditions. Two to three whorls of plants in polybags were grown in the glasshouse and subjected to two water treatments which were well-watered and water stress by withholding irrigation for 14 days. Physiological traits (chlorophyll pigments, membrane stability and epicuticular wax content), relative water content, and proline and sucrose contents were observed. After commencing the water stress condition for 14 days, all four clonal seedlings showed significantly decreased leaf relative water content. In addition, variation was discerned in leaf cell membrane stability that coincided with significantly lower membrane injury. An increasing trend in proline content from day seven to 14 and a comparable sucrose content in leaf tissue throughout the experiment were also observed. RRIM 2023 exhibited the highest membrane stability, whilst RRIM 2020 was severely affected, which reflected on their low ability to withstand water stress. A similar trend was observed for epicuticular wax content, chlorophyll b and total chlorophyll of RRIM 2023 compared to RRIM 2020. Hence, membrane stability supported by epicuticular wax content and chlorophyll levels revealed RRIM 2023 as the most resilient to water stress.