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Abstract Detail


Water Relations

Wada, Hiroshi [1], Matthews, M.A. [2], Shackel, Ken [3].

Apoplastic solute accumulation accounts for turgor loss and fruit softening in grape (Vitis vinifera L.) berries.

Cell wall modification plays an important role in fruit softening, but fruit cell turgor (P) may also be involved. The development of the grape (Vitis vinifera L.) berry is often described as a three stage process in which growth occurs in Stages I and III, separated by a lag (Stage II), and where ripening begins with the transition between Stages II and III. Loss of mesocarp P occurs at the beginning of ripening, and is strongly correlated to softening. We used both a low speed centrifuge technique and a novel pressure membrane (PM) apparatus for the extraction of apoplastic fluid from berries and tested the hypothesis that P loss was associated an accumulation of solutes in mesocarp apoplastic space. The fruit apoplastic osmotic potential (ΨsA) obtained with the PM technique agreed with that obtained by centrifugation. A clear decline in ΨsA began during Stage II, prior to the decline in P, fruit firmness, and the ΔΨs between symplast (tissue) and apoplast. Thereafter, both apoplast and fruit tissue osmotic potential decreased dramatically, both reaching almost -4 MPa by late in fruit development. When the composition of the recovered apoplastic sap was analyzed, potassium, malate, tartrate, proline, glucose, fructose, and sucrose were detected. The summed concentration of all solutes during Stage I was very low. Fructose and glucose increased significantly during Stage II, and became the predominant solutes in Stage III where the composition of the measured solutes accounted for most (86%) of the measured ΨsA. Therefore, our results support the hypothesis that a decrease in ΨsA is responsible for the observed loss in mesocarp P, and suggest that a loss in P is the primary mechanistic cause of fruit softening in grape.


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1 - University of California, Davis, Department of Viticulture and Enology, One Shields Avenue, Davis, CA, 95616, USA
2 - University of California, Davis, Department of Viticulture and Enology
3 - University of California, Davis, Department of Plant Sciences

Keywords:
Fruit ripening
Fruit development
Matric potential.

Presentation Type: Plant Biology Abstract
Session: P
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM
Number: P09007
Abstract ID:353


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