The Physiological Basis Of Latex Flow Promoting By Ethrel And Low Temperature In Hevea Brasiliensis

Natural rubber is made from latex of rubber tree. Duration of latex flow, time of sustaining latex flow out of the cut bark, directly determines rubber yield. Ethrel is the most effective stimulant apllied in natural rubber production since it significantly prolongs the duration of latex flow. It is interesting that low temperature has the same effect as ethrel with this respect. However, mechanism for the effect of ethrel and low temperature on prolonging the duration of latex flow remains largely unknown. Elucidation of the mechanism will aid to understand the mechanism of laticifer plug formation and latex flow, and develop new type of stimulant for promoting latex flow. This paper investigated the effect of ethrel and low temperature on several physiological parameters of latex from rubber tree clones, Reyan8-79and PR107, which are different in the property of latex flow. In addition, investigation was also involved in the effect of ethrel on the changes in bursting index of lutoid and the level of mercaptan and hydrogen peroxide in latex of rubber tree clones, Reyan7-33-97, Reyan8-79, and PR107, within24hours. Results as follows:(1) C-serum obtained by centrifugation of latex collected with equal volume of iso-osmia buffer (0.4M mannitol+0.1M Tris-HCl, pH7.2) was suitable for the determination of the activity of free acid phosphatase in latex while the latex diluted with hypotonic buffer containing0.1%TritonX-100together with shaking and freeze thawing was suitable for the determination of total acid phosphatase.(2) The level of mercaptan in the latex from rubber tree clone Reyan8-79was significantly higher than that from rubber tree clone PR107, but for the parameter, the bursting index of lutoid, the reverse was right.(3) Upon treatment with ethrel, duration of latex flow prolonged, the bursting index of lutoid increased while the initial rate of latex flow decreased in both the rubber tree clones, Reyan8-79and PR107. The effect of ethrel attenuated afer the third tapping.(4) After stimulating by ethrel for24h, Several physiological parameters in the latex from Reyan8-79followed the similar fluctuational pattern with that from PR107, but reverse to that from Reyan7-33-97.(5) Low temperature caused to significantly decrease in bursting index of lutoid while increase in the level of mercaptan, which was in contrast to the case of ethrel treatment.On the basis of the results as above, two conclusions were tentatively drawn:(1) The level of mercaptan in latex is rubber tree clone-characteristic and positively correlated to the duration of latex flow.(2) The mechanism for prolonging of duration of latex flow caused by low temperature is different from that caused by ethrel application.