Mesocarp cell turgor in Vitis vinifera L. berries throughout development and its relation to firmness, growth, and the onset of ripening

Abstract

Vitis vinifera L. berries are non-climacteric fruit that exhibit a double sigmoid growth pattern and dynamic changes in gene expression, cell metabolism, and water relations at the onset of ripening. The cell-pressure probe was utilized to examine the relationships of turgor pressure (P) in mesocarp cells to growth, sugar accumulation, and fruit softening during development. In replications utilizing three different varieties, mesocarp cell P demonstrated a consistent pattern of a relative mid-range P early in development, followed by an increase to a maximum of about 0.35 MPa, and a subsequent rapid decline before ripening to less than 0.1 MPa. Fruit "apparent elastic modulus" (E, units of MPa), was introduced as a standard measure to describe ripening-related softening. E changed dynamically and synchronously with P during development and in response to water deficits for fruit grown in greenhouse and field conditions. Thus, E and P were positively and linearly related. Sugar accumulation did not increase significantly until P had declined to less than 0.1 MPa. The results suggest that P is an important determinant of fruit softening and that P decreases in conjunction with many of the physiological and gene expression changes that are known to occur at the onset of ripening.

Water Transport Properties of the Grape Pedicel during Fruit Development: Insights into Xylem Anatomy and Function Using Microtomography

“…For grape, several physiological parameters of the fruit (e.g. growth, sugar accumulation, turgor, and firmness) change before veraison (Thomas et al, 2008;Wada et al, 2008Wada et al, , 2009Matthews et al, 2009), which is in line with the early developmental changes in pedicel k h . The decrease in berry growth from stage I to stage II, which is a normal part of their development, may be directly related to the reduction in hydrostatic and osmotic pedicel k h , which can reduce water transport capacity along the extracellular and intracellular pathways, respectively, between the parent plant and fruit.…”

Vascular functioning and the water balance of ripening kiwifruit (Actinidia chinensis) berries

“…If growth occurs when water moves towards expanding cells down a water potential gradient (Boyer and Silk, 2004), why do xylem fluxes not substitute for phloem water after girdling and allow growth to continue, at least temporarily? A potential explanation is that turgor in the maturing fruit is already close to zero (Thomas et al , 2008); following girdling, a decrease in turgor and growth-sustaining water potential large enough to compete for already limited xylem water may not be possible (Boyer and Silk, 2004). Girdling may also prevent continued solute accumulation by expanding cells.…”

Not All Shrivels Are Created Equal—Morpho-Anatomical and Compositional Characteristics Differ among Different Shrivel Types That Develop during Ripening of Grape (<i>Vitis vinifera</i> L.) Berries

“…Since phloem influx serves as the predominant source of water and solutes for the ripening berries to gain weight and volume after veraison [111], and the fact that BS berries accumulated meager amount of solutes (sugars), their shriveling phenomenon reflected more of a loss of phloem functionality after verasion [17,88] rather than sole involvement of water efflux either by cuticular transpiration or backflow into the vine as suggested for PD berries. Accordingly, the flaccidity of the pericarp originnated from a lack of continual turgor pressure required for expansive growth [112] and sugar accumulation [83], which failed to occur due to a decrease in mesocarp cell viability [106].…”