Analysis of Reduced Photosynthesis in the Apple Leaf under Sink-limited Conditions Due to Girdling

Abstract

On the 6th day after girdling, the photosynthesis rate of leaves on the 3-year-old stem, 2-year-old stem and new shoot of a branch of a field-grown 4-year-old apple tree decreased. The starch content in the leaves, bark and wood significantly increased, especially in shoot leaves. In the girdled branch, concomitant with the photosynthesis reduction, on the 6th day after girdling, the stomatal conductance of leaves on the 3-year-old stem, 2-year-old stem and new shoot declined. Under this condition, a significant correlation between the photosynthesis rate and stomatal conductance could be recognized. On the other hand, with girdling, the activity of ribulose-1,5-bisphosphate carboxylase (RuBPcase) per leaf area decreased on the basis of the decrease in RuBPcase activity per unit enzyme protein. The initial activity of RuBPcase per leaf area in shoot leaves decreased. Moreover, the activity of RuBPcase per leaf area significantly correlated with the photosynthesis rate. Based on these results, it is suggested that the decrease in the photosynthesis rate of the sink-limited branch of a young apple tree 6 days after girdling is mainly caused by closing of the stomatal aperture and reduction of RuBPcase activity per leaf area.

Tree Girdling: A Tool to Improve Our Understanding of Coupled Sugar and Water Transport

“…Hence, it is likely that double girdling expedited the carbon unloading of the stem tissue close to the phloem blockage. Some girdling studies observed a similar increase in soluble carbohydrates in zone U (Li et al, 2003), while other studies did not (Daudet et al, 2005;Cheng et al, 2008). Cheng et al (2008) and Li et al (2003) performed girdling (DOY 262 and 268, respectively) close to the girdling date of our experiment, while Daudet et al (2005) girdled earlier in the growing season (DOY 193).…”

“…2). The decrease in upward sap flow was probably caused by a feedback inhibition of P n (Williams et al, 2000;Cheng et al, 2008;Domec and Pruyn, 2008). The observed trends of a decrease in P n and an increase in R d after girdling ( Fig.…”

“…Several girdling studies (Iglesias et al, 2002;Bondada and Syvertsen, 2005;Johnsen et al, 2007;Cheng et al, 2008;Rivas et al, 2008) have reported this P n inhibition which they attributed to the decreased sink demand in girdled trees. In literature two processes are described which might trigger inhibition of P n : stomatal closure (Williams et al, 2000;Cheng et al, 2008;Domec and Pruyn, 2008) and damage to the photosynthesis system (Myers et al, 1999;Bondada and Syvertsen, 2005;Rivas et al, 2008). Cheng et al (2008) observed that these two processes occur simultaneously.…”

Metabolism and Accumulation of Sugars Translocated to Fruit and Their Regulation

“…Sink strength can regulate photosynthesis. That is, if sink strength was reduced in the sinklimited condition of apple trees by girdling, Rubisco and photosynthesis activities in leaves decreased (Chen et al, 2008). Thus, comparing sink activity with RGR is important.…”

Regulation of Leaf Photosynthesis Through Photosynthetic Source-Sink Balance in Soybean Plants

“…However, there is also evidence from high CO 2 treatment experiments using various C 3 plants that decreased Rubisco activity in leaf rather than changes in leaf Rubisco content is likely to be a main cause (Sage et al, 1989). Data from experiments conducting excisions of sink organs (pods or flower buds and flowers) or petiole girdling suggest that a decrease of stomatal conductance or Rubisco activity or Rubisco content in leaf, or both decreases of Rubisco activity and Rubisco content in leaf can be responsible for the decrease in leaf photosynthetic rate under excessive photosynthetic source capacity (Mondal et al, 1978;Wittenbach, 1982Wittenbach, , 1983Xu et al, 1994;Crafts-Brandner & Egli, 1987;Cheng et al, 2008). As described in the Introduction, excising sink organs or high CO 2 treatment can have side effect(s) other than inducing excessive photosynthetic source capacity.…”