Physiological and Productivity Impact of Mechanical Wounding and Mortex Stimulation on Rubber Clones RRIM 2025 and PB 350

Abstract

The effects of mechanical wounding involving mechanical boring and tapping followed by the application of Mortex, an ethylene-based stimulant, on Hevea clones RRIM 2025 and PB 350 were investigated. Mortex at three different concentrations of 0.75%, 2.5% and 5% were applied at the tapping panel and the response of both clones in influencing wound-induced ethylene, latex yield, sugar, thiol and proline contents were determined. Data were analysed against control 1 (untapped and unstimulated), control 2 (tapped and unstimulated) and the application of nanosilver solution (Silversol), an ethylene inhibitor containing Ag+. Latex yield of both clones appeared to be induced and dependent on ethylene stimulation. Mortex at 2.5% was suggested to be optimum for high yield stimulation in both clones. Application of 5% Mortex gave the highest yield for both clones and induced highest wound-induced ethylene release in the shaved bark of RRIM 2025. Meanwhile, 2.5% Mortex gave the highest wound ethylene evolution in shaved bark of PB 350. Wounding by tapping alone produced wound ethylene at low levels in both clones. The very low levels of accumulated wound ethylene found in bored holes at 2 cm above tapping cut was likely due to tapping activity and not influenced by Mortex application. Silversol was found to successfully inhibit ethylene action by reducing wound ethylene release in shaved bark of both clones. Reduced sucrose content in the latex with 5% Mortex was observed. In contrast, unstimulated trees and an application of Silversol appeared to reduce latex yield in both clones with a concomitant increase in sucrose content. Suppression of ethylene action by Ag+ also reduced thiol and inorganic phosphorus content, suggesting that Silversol was effective in overcoming the stress effects related to ethylene regulation.