Vascular Function in Grape Berries across Development and Its Relevance to Apparent Hydraulic Isolation

Abstract

During the latter stages of development in fleshy fruit, water flow through the xylem declines markedly and the requirements of transpiration and further expansion are fulfilled primarily by the phloem. We evaluated the hypothesis that cessation of water transport through the xylem results from disruption or occlusion of pedicel and berry xylem conduits (hydraulic isolation). Xylem hydraulic resistance (R h ) was measured in developing fruit of grape (Vitis vinifera 'Chardonnay') 20 to 100 d after anthesis (DAA) and compared with observations of xylem anatomy by light and cryo-scanning electron microscopy and expression of six plasma membrane intrinsic protein (PIP) aquaporin genes (VvPIP1;1, VvPIP1;2, VvPIP1;3, VvPIP2;1, VvPIP2;2, VvPIP2;3). There was a significant increase in whole berry R h and receptacle R h in the latter stages of ripening (80-100 DAA), which was associated with deposition of gels or solutes in many receptacle xylem conduits. Peaks in the expression of some aquaporin isoforms corresponded to lower whole berry R h 60 to 80 DAA, and the increase in R h beginning at 80 DAA correlated with decreases in the expression of the two most predominantly expressed PIP genes. Although significant, the increase in berry R h was not great enough, and occurred too late in development, to explain the decline in xylem flow that occurs at 60 to 75 DAA. The evidence suggests that the fruit is not hydraulically isolated from the parent plant by xylem occlusion but, rather, is "hydraulically buffered" by water delivered via the phloem.

Formação e maturação da uva e os efeitos sobre os vinhos: Revisão

“…Após o início da maturação, observa-se uma restrição do fluxo de água para as bagas nos feixes vasculares axiais (ou centrais) do xilema. Porém, tem sido demonstrado que muitos feixes vasculares periféricos continuam a se diferenciar mesmo após o pintor (Keller et al, 2006;Chatelet et al, 2008), que a capacidade de transporte continua sendo mantida durante a maturação, possibilitando o reaproveitamento do excesso de água do floema (Choat et al, 2009) e que a interconexão entre os vasos possibilita a manutenção do fluxo via xilema (Keller et al, 2006). Além disso, a diminuição no fluxo do xilema relatada neste período deve-se a perda da pressão hidrostática do apoplasto, como resultado da modificação do padrão de partição dos solutos (simplasto/apoplasto) ao longo do dia (Chatelet et al, 2008).…”

The Grapevine Root-Specific Aquaporin VvPIP2;4N Controls Root Hydraulic Conductance and Leaf Gas Exchange under Well-Watered Conditions But Not under Water Stress

“…Primers for the endogenous and transgenic VvPIP2;4N sequences were designed using Primer Express 3.0 software (Applied Biosystems; http// www.appliedbiosystems.com/), while primers previously reported by Choat et al (2009) were used to amplify VvPIP2;1, VvPIP2;2, VvPIP2;3, and VvPIP1;1 (Supplemental Table S2). First-strand cDNA synthesis was performed using the High Capacity cDNA Reverse Transcription kit (Applied Biosystems), and PCR was performed using PowerSYBR Green master mix (Applied Biosystems).…”

“…Expression of some of these genes, belonging to the PIP and Tonoplast Intrinsic Protein subfamilies, has been studied in grape berry (Picaud et al, 2003;Fouquet et al, 2008;Choat et al, 2009) and vegetative tissues (Baiges et al, 2001;Vandeleur et al, 2009). The results of these studies suggest that aquaporins have important roles in facilitating water redistribution within the growing berry (Picaud et al, 2003;Fouquet et al, 2008;Choat et al, 2009) and in regulating adaptation to water stress (Vandeleur et al, 2009). However, these results, being based on correlations between the expression of aquaporin genes and morphological and physiological observations, lack reliable in vivo functional evidence.…”

Alterações anatômicas do sistema vascular em porta-enxertos de videira

“…Modificações do sistema vascular ocorrem em diferentes espécies frutíferas (Olmstead et al, 2006;Rodríguez-Gamir et al, 2010;Tombesi et al, 2010), com influências sobre a formação dos frutos (Choat et al, 2009) e a incidência de doenças (Thorne et al, 2006;Chatelet et al, 2011). Estas alterações afetam processos fisiológicos como a resistência hidráulica e a suscetibilidade ao embolismo (Brodersen et al, 2010;Lucas et al, 2013).…”