RELATION BETWEEN HORMONAL BALANCE AND POLYGALACTURONASE ACTIVITY IN GRAPE BERRY

Grape berry Vitis vinifera L. is a non climacteric fruit that exhibits a double sigmoïdal pattern of growth.
The first phase corresponds to cellular multiplication and growth.
Ripening occurs concomitantly with the second growth phase and involves significant changes.
Sugar accumulation and colour change are well known.
Many changes in cell wall polymer properties occur during softening and the implicated mechanisms are still unclear.
Abscisic acid (ABA) and indole acetic acid (IAA) levels during grape berry development have been evaluated.
The free ABA content of whole berries and separated pericarp increases during the change of colour.
ABA accumulation is concomitant with a peak in IAA level.
ABA seems to have a specific repartition between the different tissues of the berry during the development.
Our results indicate that the pulp looses its ABA during ripening.
On the contrary, ABA increases in the skin tissue.
Calcium ion concentration develops in the same way while the skin tissue water content decreases.
ABA may be involved in protein synthesis such as cell wall-modifying enzymes.
Polygalacturonase (PG) activity is detected during colour change period and seems to be well correlated with ABA levels in the berry.
We also note two types of development in the PG activity profile: In several cultivars, the berries show an increase of PG activity during change colour period whereas this activity appears earlier, at the beginning of change colour process for other Bordeaux cultivars.
These results are also well correlated with free galacturonic acid levels in berry must.

V International Postharvest Symposium

C. Deytieux, L. Gény, B. Donèche

abscisic acid, change of colour, indole acetic acid, softening, skin, wall

https://doi.org/10.17660/ActaHortic.2005.682.15