Berry pericarp ontogenesis from fertilization to maturity of <em>Vitis vinifera</em> L. var Merlot

Abstract

Grape-flower ovary transformations is followed from fertilized flower to berry came to maturity. Cell transformations are studied, especially vacuolar tannins, starch and cell wall thinning : - From fruit setting to veraison, cell number of carpellary wall located between outer epidennis and vascular bundles is multiplied by 2. - Cell size increase considerably but by different means according to tissues: hypodennis cells elongate tangentially while inner parenchyma cells round. - Vacuolar tannins content in internal parenchyma cells decrease as soon as ovary is fertilized. During growth and veraison tannic cell number decrease. At maturity, only the most external cells (superficial hypodennis) still have vacuolar tannins. All the other cells of ovary wall have no more tannins. - Wall thickness decrease begins as soon as growth starts and this phenomena is continuous to maturity. The wall thinning down begins near the locules of ovary and is propagated towards the ouside of pericarp. - Amyloplasts disappear progressively. At maturity, there is scarcely no more startch in grape-berry. In short, except cells of berry skin, all the cells of ovary wall enlarge, lost their vacuolar tannins and the cell walls become very thin ; they are pulp cells. ln the pericarp of mature berry, hypodennis is very thin (less than 50 μm in places and 2-5 layers of cells). Pulp or flesh takes up a great place. This work is consecutived to the one on ovary before fertilization (FOUGÈRE-RIFOT et al., 1995) that shown 20 development stages from ovary primordia to the fertilized egg. From fertilized ovary to mature berry the development of pericarp is divided into 5 stages (stages 21 to 25) : - Stage 21 : first appearance of ovary inflation. Ovary takes a round shape. The thickness of carpellary wall is about 300 μm. - Stage 22 : fruit setting. Vacuolar tannins of inner parenchym disappear. - Stage 23 : berry growth. - Stage 23A : transformation of inner parenchym into pulp. - Stage 238 : transformation of deep hypodennis into pulp - Stage 23C : pulp cell enlargement. - Stage 24 : veraison. The definitive size of the berry is about reached. - Stage 24A : beginning of veraison. The hypodermis has still some thick walls. - Stage 248 : end of veraison. The hypodennis cells near the outer pulp cells change into pulp cells - Stage 25: maturity. Pulp is became very developped.

Keywords

• Vitis vinifera
• berry
• development stages
• ovary wall
• pulp
• cell transformations
• vacuolar tannins
• cell wall thickness