CSIRO Waite Campus Seminar: Dr Gerhard Rossouw
Aug 27, 4:00 pm
The following seminar will take place at 4:00 pm on Tuesday 27th August in the CSIRO Wine Innovation West, Upstairs Seminar Room.
Corner Hartley Grove & Paratoo Rd, Waite Campus Urrbrae
Grapevine Carbohydrate and N allocation during berry ripening: Impacts of water status and leaf area
Dr Gerhard Rossouw | Research Technician, CSIRO Agriculture and Food
Carbohydrates assimilated through leaf photosynthesis are promptly translocated to ripening fruit to support berry sugar accumulation. Starch reserve storage in perennial tissues, however, also commences late in the season likely prior to fruit maturity. The roots, a permanent sink, may therefore compete with berries, a temporary sink, for the assimilated carbohydrates. Some berry N accumulation is additionally expected to occur during ripening, while the perennial tissues usually start replenishing N reserves before fruit maturity. Therefore, the roots and berries may also compete for N during fruit ripening. When canopy photosynthesis and soil N absorption are restricted, however, carbohydrate and N reserves may be remobilised from storage pools to contribute towards fruit sugar and N.
The aim of this work was to evaluate the allocation of non-structural carbohydrates and N among the different grapevine organs, as influenced by water supply and source-sink biomass ratios during berry ripening. Pot experiments were conducted to evaluate whole vine and organ specific changes in biomass, carbohydrate and N content, and primary metabolite abundance until fruit maturity. Root carbohydrate reserves supported fruit sugar accumulation when water constraints and/or reduced leaf area restricted canopy photosynthesis. However, root starch reserves were replenished as soon as fruit sugar accumulation slowed. During sustained water constraints, root starch hydrolysis during peak fruit sugar accumulation yielded sucrose, which is transportable to berries to support the sugar content. Myo-inositol metabolism seemingly played a distinct role during root starch remobilisation. In contrast to the roots being an important carbohydrate source when photosynthesis was restricted, leaf N seemed to contribute to fruit N during sustained water constraints. Furthermore, root N reserve storage is inhibited when water constraints are sustained during fruit ripening. While the root total N content was little affected by defoliation, the amino N composition was altered, prompting accumulation of amino acids. Amino acids similarly accumulated in the fruit of defoliated vines, effectively increasing the yeast assimilable N. Water constraints or reduced leaf area during berry ripening inhibits starch reserve storage, impacts carbohydrate metabolism in source and sink organs, and alters amino N composition in roots, leaves and berries. These alterations in grapevine physiology may not only affect fruit composition during the current season, but also vegetative and reproductive development during the following season
About the Speaker
Gerhard Rossouw completed his BSc and MSc studies at the University of Stellenbosch, South Africa before working in the wine industry as a viticulturist and in wine production for several years. Gerhard subsequently completed his PhD at Charles Sturt University in early 2017, focussing on carbohydrate and nitrogen distribution and utilisation in grapevines. Upon completion of his PhD, Gerhard spent 18 months teaching viticultural sciences and vineyard management at Charles Sturt University, whilst also studying the implications of herbicide drift on grapevine vegetative and reproductive development. Gerhard is currently involved in the regional evaluation of CSIRO’s first generation powdery and downy mildew resistant grapevines
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