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Sanam Chai Khet, Thailand

Chantuma P.,Chachoengsao Rubber Research Center | Lacote R.,CIRAD - Agricultural Research for Development | Leconte A.,Kasetsart University | Gohet E.,CIRAD - Agricultural Research for Development
Field Crops Research | Year: 2011

In Thailand, the continuous decrease in the size of rubber plantations has led to the general adoption of intensive tapping systems which may lead to over harvesting, high rates of tapping panel dryness (TPD), short life-cycles of the plantations, and low labour productivity. In Thailand, farmers use a half-spiral downward tapping system (S/2) or a one third-spiral (S/3) with a tapping frequency of once two days (d2) or more. To increase productivity, it is difficult to reduce tapping frequencies, even with ethylene stimulation, as this would result in days without work for tappers. The purpose of this study was to characterize the behaviour of the Hevea latex yield under the double cut alternative tapping system (DCA). The aim was ensure the long-term sustainability of latex yield by increasing the time required for latex regeneration between two tappings through splitting this high tapping intensity (100% or above) into two different tapping cuts tapped alternately (S/2 d47d7(t,t). Over a period of 10 years, compared to a single cut tapping system (S/2 d2) of equivalent intensity, DCA increased cumulative rubber production by 9%. Ability of the trees to produce more latex under DCA was related to the sucrose and inorganic phosphorus contents of the latex cells in each tapping panel. DCA produced metabolic activity more favourable to yield during the first 10 years of tapping. But DCA also resulted in higher TPD rates, a sign of a metabolic dysfunction of the productive bark. DCA is a new tapping system. Further research is required to optimize the use of the DCA strategy. Such research will lead to new advances in our knowledge of the physiology of the rubber tree, mainly at the trunk scale. © 2011 Elsevier B.V.

Kunjet S.,Burapha University | Thaler P.,CIRAD - Agricultural Research for Development | Thaler P.,Kasetsart University | Gay F.,CIRAD - Agricultural Research for Development | And 5 more authors.
Kasetsart Journal - Natural Science | Year: 2014

This research improved the model for the radial distribution of the sap flux density in rubber trees. The objective of the study was to describe the radial variability of xylem sap flux in rubber trunks. The experiment was conducted in mature rubber trees aged 13 yr from clone RRIM 600, in a non-traditional planting area at the Chachoengsao Rubber Research Center from January to December 2007. The sap flow was measured by the heat dissipation method using home-made radial probes and then calibrated with the cut stems of rubber tree in the laboratory. The radial variability was modeled as a function of the depth into the xylem. Regression analysis was carried out using data on the sap flux density and depth into the xylem. The model used two basic assumptions: (1) young xylem (0-4 cm) has the maximum sap flux density and is stable and (2) sap flux density decreases linearly with the depth into the xylem (and thus older xylem) toward the center of the stem. The results showed that the model for radial distribution can be used to predict the sap flux density and to estimate the tree transpiration of different trunk diameters in rubber trees. The tree transpiration was highly variable with different girths of the rubber trees. © 2014 Kasetsart University.

Kunjet S.,Kasetsart University | Thaler P.,CIRAD - Agricultural Research for Development | Thaler P.,Kasetsart University | Gay F.,CIRAD - Agricultural Research for Development | And 5 more authors.
Kasetsart Journal - Natural Science | Year: 2013

Transpiration at the leaf and stand level is mainly controlled by climatic conditions. The diurnal dynamics of stand transpiration and stomatal conductance were analyzed in rubber trees. The experiment was conducted using 13 yr-old rubber trees from clone RRIM 600 under natural conditions at the Chachoengsao Rubber Research Center during January to December 2007, with sampling in the dry season, the rainy season and early in the dry season. At the stand level, the stand transpiration was monitored using sap flow measurement and estimated evapotranspiration from meteorological data. At the leaf level, the stomatal conductance was measured using a portable photosynthesis system on the leaves exposed to the sun. The leaf water potential was measured using a pressure chamber and the soil water content was measured by the gravimetric method. Climatic measurements were recorded using a weather station above the canopy. The plant water status was correlated with the climatic conditions and soil water content. The diurnal dynamics of stand transpiration and stomatal conductance were mainly controlled by the vapor pressure deficit and net radiation. The stomatal conductance was more sensitive to climatic variations than stand transpiration. There were different time lags between the stomatal conductance and stand transpiration throughout the year. The relationship between the climatic factors and transpiration varied throughout the year.

Kunjet S.,Kasetsart University | Thaler P.,Kasetsart University | Gay F.,Kasetsart University | Chuntuma P.,Chachoengsao Rubber Research Center | And 2 more authors.
Kasetsart Journal - Natural Science | Year: 2013

The impact of drought conditions on the water relations of rubber trees is important because the trees could shed leaves while they are being continuously tapped. The aim of this work was to study the effect of soil drought and the tapping of latex on the water relations of rubber trees. This study distinguished between untapped trees and trees affected by tapping activity. The experiment was conducted on 14-15 year-old rubber trees from the clone, RRIM 600, at the Chachoengsao Rubber Research Center (CRRC). Climatic measurement, soil water content, predawn and midday leaf water potential, stand transpiration and percentage loss of hydraulic conductivity (PLC) were measured from January 2009 to January 2010, especially in the dry season. Under drought conditions, during the rainy season, stand transpiration and predawn leaf water potential decreased in response to soil drought in August. The midday leaf water potential and PLC did not change following soil water stress. In the dry season, the plant water status was related to climatic variables and soil drought. The results indicated that drought induces a reduction in the plant water status of rubber trees. Tapping activity did not have a marked influence on the water balance of the rubber trees. However, tapping reduced the sap flux density and stomatal conductance; thus, attention must be paid to tapping in the dry season, particularly in dry areas.

Ruderman S.,Kasetsart University | Ruderman S.,Chachoengsao Rubber Research Center | Kongsawadworakul P.,Mahidol University | Viboonjun U.,Mahidol University | And 2 more authors.
Kasetsart Journal - Natural Science | Year: 2012

Expressions of the 22 genes involved in rubber biosynthesis, from the acetyl CoA genesis and the mevalonate (MVA) pathway to IPP polymerization, were analyzed by real-time polymerase chain reaction (PCR). The results revealed that the expressions of most genes were not related to the latex yield trait when compared among three high- and three low-yielding rubber clones. Only the genes HMGR3 and SRPP1 were significantly up-regulated in low-yielding clones. The higher expression of the SRPP1 gene in low-yielding clones suggested a possible increase in the number and higher rubber biosynthetic activity of the active small rubber particles, which may produce latex with higher viscosity, impairing the latex flow and limiting the latex yield. The up-regulation of the HMGR3 gene in low-yielding clones may reflect a higher amount or activity or both of Frey-Wyssling particles (plastids) in their latex. These plastids have been shown to be involved in oxidative processes that induced earlier laticifers plugging, which also impaired the latex flow and yield. In conclusion, a possible crossover between the cytosolic M VA and the plastidic 1-deoxy-D-xylulose-5-phosphate/2-C-methyl-D-erythritol-4-phosphate (DXP/ MEP) pathways is suggested, which might especially take place in the laticifers of the high-yielding clones, to fulfill the requirement in isopentenyl pyrophosphate for more active rubber biosynthesis.

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