Relationship between Fruit Soluble Solid Content and the Sucrose Concentration of the Phloem Sap at Different Leaf to Fruit Ratios in Tomato

Abstract

Tomato fruits accumulate most of their solid contents during rapid fruit development. The balance of water transport to assimilate transport into fruits during that stage is an important factor that determines the final solid content of fruits at harvest. In this study, the relationship of sucrose concentration of the phloem sap to the solid content of rapidly growing fruits was investigated. At the anthesis of the second truss, the stem just above the first truss was heat-girdled, while newly emerging leaves above the second truss were pinched regularly to diminish cross translocation of carbohydrates between the source-sink unit, consisting of the second truss and three leaves below, and other parts of the plant. The leaf to fruit ratio (LFR) as the number of leaves per fruit of this isolated source-sink unit was manipulated at the fruit set of the truss. When LFR was increased from 0.2 to 1, fruit dry weight increased linearly from 3.5 to 7 g, but it saturated beyond the LFR of 1. By contrast, the contents of dry matter and soluble sugars on a fresh weight basis increased linearly within the whole range of LFR from 0.2 to 3. The sucrose concentration of the phloem sap, collected from the pedicel by the modified EDTA method, also increased as LFR increased, and a positive correlation was observed between sucrose concentration of the phloem sap and the contents of dry matter and total soluble sugars. These data suggested that solid content can be increased in a wide range of LFR in proportion to the sucrose concentration of the phloem sap.

Heat girdling does not affect xylem integrity: an in vivo magnetic resonance imaging study in the tomato peduncle

“…While in woody tissue, girdling can be achieved by mechanical removal of the bark, the same is not always feasible for herbaceous pedicels and peduncles. The girdling of the pedicel or peduncle can then be achieved by the application of heat, through steam (Lang & Thorpe, 1989), hot water poured over the tissue (Jan & Kawabata, 2011), or an electrical current applied to a resistance attached to the tissue (Creasy & Lombard, 1993;Greenspan et al, 1994;Else et al, 1996;Guichard et al, 2005;Clearwater et al, 2012;de Freitas et al, 2014;Hanssens et al, 2015). As the latter method is easily reproducible and controllable, it has most often been used when mechanical girdling is impossible or impractical.…”

“…This method has been used on a wide range of fruits and berries, such as apple (Lang, 1990;Lang & Volz, 1998;Morandi et al, 2011), cherry (Athoo et al, 2015;Br€ uggenwirth et al, 2016), citrus (Garcia-Luis et al, 2002), grape (Lang & Thorpe, 1989;Creasy & Lombard, 1993;Greenspan et al, 1994Greenspan et al, , 1996Rogiers et al, 2001), kiwifruit (Clearwater et al, 2009(Clearwater et al, , 2012Morandi et al, 2012;Torres-Ruiz et al, 2016), mango (Nordey et al, 2015), peach (Morandi et al, 2007(Morandi et al, , 2010, pear (Morandi et al, 2014a,b) and tomato (Else et al, 1996;Plaut et al, 2004;Guichard et al, 2005;Jan & Kawabata, 2011;de Freitas et al, 2014;Hanssens et al, 2015). While in woody tissue, girdling can be achieved by mechanical removal of the bark, the same is not always feasible for herbaceous pedicels and peduncles.…”

Differences in Water and Assimilate Fluxes in Tomato Fruits among Cultivars, and Relationships with Fruit Yield and Soluble Solids Content

“…Although fruit respiration also affects fruit SSC, it can be neglected because it is much smaller than the dry matter increase (Grange and Andrews, 1995). Although there is no information about differences in the sugar contents of phloem sap among cultivars, the contents of soluble sugars, starch, and organic acids in phloem sap change with source to sink ratios (Jan and Kawabata, 2011), so they could differ among cultivars. Therefore, SSC was not completely explained by the phloem influx per fruit weight increase at 14-16 and 28-30 DAF, but the above can be important parameters to predict fruit SSC.…”

Effects of source-sink alteration by pruning on physiological parameters and fruit production of Rosa roxburghii Tratt. on the Yunnan-Guizhou Plateau in China

“…in summer, regardless of pruning time or intensity, it increased the nutritional growth vitality of blueberries and reduced the incidence of leaf diseases (Kovaleski et al 2015). The source-sink relationship played an important role in fruit yield and fruit size distribution, which was one of the hot issues in the physiological research of the high-product fruit trees (Jorquera-Fontena et al 2016). Pruning, thinning flowers and fruits, protecting flowers and fruits, fruit bagging techniques used in fruit tree cultivation and management were essentially based on the principle of the source-sink relationship (Poni et al 2018).…”