Carbohydrate storage in wood and bark of rubber trees submitted to different level of C demand induced by latex tapping

Abstract

When the current level of carbohydrates produced by photosynthesis is not enough to meet the C demand for maintenance, growth or metabolism, trees use stored carbohydrates. In rubber trees (Hevea brasiliensis Muell. Arg.), however, a previous study (Silpi U., A. Lacointe, P. Kasemsap, S. Thanisawanyangkura, P. Chantuma, E. Gohet, N. Musigamart, A. Clement, T. Améglio and P. Thaler. 2007. Carbohydrate reserves as a competing sink: evidence from tapping the rubber tree. Tree Physiol. 27:881-889) showed that the additional sink created by latex tapping results not in a decrease, but in an increase in the non-structural carbohydrate (NSC) storage in trunk wood. In this study, the response of NSC storage to latex tapping was further investigated to better understand the trade-off between latex regeneration, biomass and storage. Three tapping systems were compared to the untapped Control for 2 years. Soluble sugars and starch were analyzed in bark and wood on both sides of the trunk, from 50 to 200 cm from the ground. The results confirmed over the 2 years that tapped trees stored more NSC, mainly starch, than untapped Control. Moreover, a double cut alternative tapping system, which produced a higher latex yield than conventional systems, led to even higher NSC concentrations. In all tapped trees, the increase in storage occurred together with a reduction in trunk radial growth. This was interpreted as a shift in carbon allocation toward the creation of reserves, at the expense of growth, to cover the increased risk induced by tapping (repeated wounding and loss of C in latex). Starch was lower in bark than in wood, whereas it was the contrary for soluble sugars. The resulting NSC was twice as low and less variable in bark than in wood. Although latex regeneration occurs in the bark, changes related to latex tapping were more marked in wood than in bark. From seasonal dynamics and differences between the two sides of the trunk in response to tapping, we concluded that starch in wood behaved as the long-term reserve compartment at the whole trunk level, whereas starch in bark was a local buffer. Soluble sugars behaved like an intermediate, ready-to-use compartment in both wood and bark. Finally, the dynamics of carbohydrate reserves appears a relevant parameter to assess the long-term performance of latex tapping systems.

Phenological and Temperature Controls on the Temporal Non-Structural Carbohydrate Dynamics of Populus grandidentata and Quercus rubra

“…Temporal shifts in tissue NSC have been broadly shown to correspond with tree phenological changes and with climatic events [8][9][10][11][12][13][14][15][16][17]. We are among the first to demonstrate the potential coupling of temperature regulated C cycling processes with temporal changes in tissue NSC concentrations [1][2][3], a result that suggests future warming may disrupt current cycles of NSC accumulation and depletion in our forest.…”

“…Stored NSC is fundamental to sustaining plant growth and metabolism during periods of high physiological stress and through dormancy, when photosynthetic C supply is low [2][3][4][5][6][7]. Because of a shifting balance between plant metabolic C demands and photosynthetic C supply, NSC concentrations in plant tissues can change on hourly to seasonal timescales [8][9][10][11][12][13][14][15][16][17].…”

How resilient is Quercus suber L. to cork harvesting? A review and identification of knowledge gaps

“…A comparable case of periodically extracted high-carbon cost product is latex from Hevea brasiliensis, continuously regenerated in tapped barks. A shift in carbon allocation toward the creation of reserves at the expense of radial growth has been regarded as a strategy to overcome repeated wounding and loss of latex (Chantuma et al, 2009;Silpi et al, 2007). In contrast with defoliation, where the lost biomass is also the photoassimilation tissue and where, for that reason, storage mobilization is not always evident (Chapin et al, 1990), the loss of cork may be compared to the investment in flowers and fruits, which do not contribute to carbon assimilation and are considerable sinks of photoassimilates.…”

Frankincense yield is related to tree size and resin-canal characteristics

“…Seeds from tapped B. papyrifera trees also showed lower germination success as compared to seeds from untapped trees Eshete et al, 2012b). Similar effects of tapping were reported for other tree species (Silpi et al, 2006(Silpi et al, , 2007Varghese and Ticktin, 2008;Chantuma et al, 2009). Developing more sustainable tapping strategies that reduce the risk of over-tapping is important for planning sustainable management of the remaining frankincense resources of species such as B. papyrifera.…”