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Felling and girdling - two common mechanical control methods - were tested as measures to combat the vegetative sprout response of the invasive tree species black cherry (Prunus serotina EHRH.). The study was carried out in pure Scots pine (Pinus sylvestris L.) stands in East Germany with the understory colonized by P. serotina (Fig. 1). The aim of the study was two-fold: (1) to assess how much biomass is generated after carrying out the felling and girdling and (2) to determine if there is a significant distinction between the different treatments in terms of sprout regrowth (biomass and number of sprouts). Regrown sprouts from 96 treated P. serotina trees were harvested (felled: N=58; girdled: N=38). The number of regrown one-year-old sprouts and the total sprout biomass were compared between the treatments. The effectiveness of repeated sprout cutback on reducing the vegetative growth response of the second regrowth was tested. The sprout development (biomass, number of sprouts, total leaf area, and branch number) was evaluated for one-year-old and two-year-old sprouts after the felling. The specific leaf area was evaluated for the treatments. The diameter of P. serotina sprouts was estimated from a regression model using sprout length as the estimate (Fig. 3). The total sprout biomass after felling was five times higher than after girdling (Fig. 4). A single sprout cutback did not affect stump vitality (Fig. 5, Tab. 3). In the second growing season, the number of branches decreased with the increasing number of sprouts after felling. The high sprout density and large total leaf area of P. serotina gave species an advantage in colonizing the understorey (Fig. 6). The total sprout biomass increased with increasing stump height after felling, whereas a similar relationship was not observed for the girdling height (Fig. 7). The specific leaf area of P. serotina decreased with increasing light availability only after girdling. A similar trend could not be detected for leaves of sprouts from the felling treatment due to the lack of reference plots in the shade (Fig. 8). Although highly labor-intense, girdling proved to be the more effective mechanical control method of P. serotina, in terms of lowering both the number and the biomass of regrown sprouts. The height of the girdle did not have a significant effect on the total sprout biomass. If felling is applied, the trees should be cut near the ground, and the treatment repeated in the consecutive year to reduce resprouting and stump vitality. [ABSTRACT FROM AUTHOR]

Sorbitol is the primary photosynthate and translocated carbohydrate in apple (Malus xdomestica), and most of it is converted to fructose by sorbitol dehydrogenase (SDH) in sink tissues. We studied the expression of nine SDH genes, SDH activity, and sorbitol content of apple 1) in buds and floral tissues from dormancy to bloom, 2) in leaves and shoot tips of trees on two rootstocks, the moderately vigorous 'Malling Merton 111' (MM.111) and the dwarfing 'Malling 9' (M.9), and 3) in shoot tips in response to application of prohexadione-Ca to suppress shoot growth and defoliation and girdling (D/G) to deprive the shoot tip of sorbitol. In mature, orchard-grown trees, sorbitol was the main soluble carbohydrate in expressed xylem sap from dormancy to bloom at levels over 3- to 6-fold those of glucose and fructose, the other major sugars present. Sorbitol levels there increased from dormancy to its highest concentration at the half inch green stage and declined by bloom, while those of the other sugars increased. SDH activity per milligram of protein increased over 4-fold from dormancy to flowering. Three of the nine known SDH genes (SDH1, SDH2, and SDH3) were expressed in immature and mature leaves and all buds from dormancy to bloom, as well as in all floral organs, except that only SDH3 transcript was found in stamen tissue. Two genes, SDH6 and SDH9, were floral-tissue specific; SDH6 transcript was detected in all floral organs except stamens at full bloom, and SDH9 was only expressed in anthers with pollen. In buds and leaves of young, container-grown trees, SDH1 and SDH2 generally accounted for the majority of total SDH expression. There were generally no effects of rootstock on SDH expression, SDH activity, or sorbitol concentration in leaves, while apical shoot tips on M.9 rootstock exhibited greater SDH activity than those on MM.111 or lateral shoot tips on either rootstock, though SDH expression of apical and lateral shoot tips on M.9 was lower than on MM.111. Prohexadione-Ca reduced apical but not lateral shoot growth, increased apical but not lateral shoot tip sorbitol content, had no effect on SDH activity, and increased SDH1 expression of all shoot tips. D/G treatment reduced shoot growth, sorbitol content, and SDH activity, but increased SDH1 expression of apical shoot tips only and SDH2 expression of lateral shoot tips only. This work indicates that sorbitol and other sugars are abundantly available from dormancy to bloom, that SDH activity increased during this period, and that SDH expression is at least in part developmentally regulated within the individual floral and leaf tissues. In shoot tips and leaves of young trees, SDH transcript level was not correlated with sorbitol availability or SDH activity, suggesting that other factors have significant regulatory effects after SDH expression on SDH activity. [ABSTRACT FROM AUTHOR]

The goal of this study was to document the relationship between fruit growth patterns and flushing number in litchi (Litchi chinensis Sonn. cv. 73-S-20). The impact of flush number on fruit retention, fruit quality, and leaf efficiency (g fruit FW produced per unit of leaf area at harvest) was assessed in field-grown 6-year-old trees by adjusting the number of flushes per bearing shoot through girdling at two fruit developmental stages. The cumulative fruit growth was sigmoidal. The greatest fruit relative growth rate (RGR) occurred during 3 to 5 weeks after full bloom (AFB), peaking on week 3 at 0.39 g· g-1 dry weight (DW) per day. The greatest fruit absolute growth rate (AGR) occurred during weeks 8 to 11, peaking on week 11 at 0.16 g· d-1 DW. Fruit retention was sensitive to girdling applied during week 3. Most fruit dropped on branches with ≤ two flushes, whereas fruit continued to develop on branches with three flushes and on the controls. There was a gradual loss of fruit when the girdling was applied during week 8. The number of fruit retained on branches with two and three flushes was similar to the controls. At harvest, regardless of the time of branch girdling, fruit yield and quality increased with increasing number of flushes; shoots with three flushes were similar to ungirdled controls. Leaf efficiency on branches girdled during week 3 was inferior to that girdled during week 8. All treatments had similar leaf efficiency when branches were girdled during week 8. On the other hand, girdling treatment applied during week 3 resulted in variable leaf efficiency among treatment, indicating that fruit were utilizing reserves in bearing shoots. We concluded that bearing shoots of '73-S-20' litchi trees require a minimum number of three flushes for adequate fruit production. [ABSTRACT FROM AUTHOR]