Fruit‐bearing branchlets are carbon autonomous in mature broad‐leaved temperate forest trees

Abstract

In order to evaluate the degree of carbon autonomy for fruit development, the carbon source-sink relationship in fruit-bearing branchlets of mature deciduous forest trees was manipulated in situ . The tests included half and complete defoliation, girdling or the combination of both treatments, which were applied on fruiting branchlets by using a canopy crane. Concentrations of non-structural carbohydrates (NSC) were analysed in different branchlet tissues and fruits, to identify situations of carbon imbalances induced by the treatments. NSC concentrations of branchlets were generally lower under treatments resulting in decreased fruit growth. All three investigated species ( Carpinus betulus , Fagus sylvatica and Tilia platyphyllos ) exhibited complete carbon autonomy of fruiting at the level of whole, undisturbed branchlets, since neither a decrease of total infructescence biomass, nor of individual fruit mass occurred on girdled, un-defoliated branchlets. On girdled, 100% defoliated branchlets, fruit biomass relative to controls decreased by approximately 50% in Carpinus and Tilia , but by almost 80% in Fagus , which can be explained by different proportions of photosynthetically active infructescence tissues among the species. In contrast to the other two species, Tilia branchlets did not import carbon to compensate for assimilate loss after defoliation.

An increase in canopy cover leads to masting in Quercus ilex

“…However, several studies have not found any evidence of reserves consumption in perennial tissues (Stevenson and Shackel 1998;Miyazaki et al 2002;Yasumura et al 2006). Such findings concur with a large fruit production depending on current-year photosynthates (Hoch 2005), which agrees with the lack of empirical evidence for any carbon limitation of masting (Körner 2003;Ichie et al 2005).…”

Does a heavy fruit crop reduce the tree ring increment? Results from a 12-year study in a subalpine zone

“…In our study, in 2009, the year of the heaviest fruit production observed in 12 years, there were no signs of a decreased ring increment in the group of trees with a high fruit crop. Another reason for the lack of a visible trade-off at the treestem level could be the modular nature of trees; branches and shoots can be quite autonomous in their resource budget and in consequence costs vary at the different canopy levels (tree canopy, branch, and shoot; Obeso 1997;Hoch 2005;Sánches-Humanes et al 2011). In Styrax obassia, Miyazaki et al (2002) showed that reproductive Fig.…”

PbWoxT1 mRNA from pear (Pyrus betulaefolia) undergoes long‐distance transport assisted by a polypyrimidine tract binding protein

“…Girdling has been used for decades to improve fruit quality and yield (Goren et al, 2004), and it is also an important technique in physiological studies of translocation and source/sink relationships (Goren et al, 2004;Hoch, 2005). Here we found that when the phloem of lateral stems was girdled at two points, the PbWoxT1 mRNA signal disappeared between the two girdling points between Day 4 and Day 6 after girdling (Fig.…”