Modification of Pattern of Photosynthate Movement within and between Shoots of Vitis vinifera L

Abstract

During the prebloom and bloom stages, no movement of labeled photosynthates occurred from a shoot of Vitis vinifera L. fed with 14CO2, to an adjacent shoot on the same spur.Movement of labeled assimilates into the unfed shoot was induced when this shoot was sprayed with 2.89 X 1O-3 The distribution of photosynthetic products from single leaves on shoots of Vitis vinifera L. has been described previously (2). During the period of shoot growth, the direction of photosynthate movement from a given source leaf changes. From a newly exporting leaf, movement is acropetal to the young leaves and shoot apex, but, with continuing growth ofthe shoot and the production of new leaves, photosynthate movement from the same leaf becomes basipetal. The pattern of photosynthate movement in the grapevine may also be altered as a result of exogenous application of herbicides (3) and growth regulators (6), indicating that changes in the relative activity, or sink capacity, of the different growth centers may influence the pattern of distribution of assimilates in the phloem system.In the experiments described here, 14CO2 and autoradiography were used to investigate the plasticity of phloem movement within and between adjacent shoots of the grapevine during the early part of the season through observation of the effects of growth substance application, leaf darkening, partial defoliation, shoot tip removal, and deblossoming on the pattern of photosynthate movement. MATERIALS AND METHODSThe grapevines used were mature vines of the variety "Muscat of Alexandria" growing in a vineyard at the University of California, Davis. A second experiment was carried out at the beginning of the bloom stage; as in the previous experiment uniform pairs of adjacent shoots were selected. A single leaf near the base of one of the shoots was fed with 50 ,uc of '4CO2, and movement of labeled assimilates into the second shoot was examined when this shoot was (a) darkened, (b) defoliated, (c) untreated but with the fed shoot decapitated (upper 7.5 cm removed) and deblossomed, (d) untreated. Darkening was achieved by enclosing the shoot in a shade constructed from aluminum foil. The defoliation, darkening, decapitation, and deblossoming treatments were applied 24 hr before the "4CO2 treatment, and the shoots were prepared for autoradiography 24 hr after the "CO2 was supplied.In the third experiment, carried out during the berry set stage, an examination was made of the effect of darkening, defoliation, and decapitation on the distribution of photosynthates within a single shoot. Uniform shoots, each having a single fruit cluster, were selected from several widely spaced vines. One leaf per shoot, either an upper leaf (newly, fully expanded) or a lower leaf (directly above the fruit cluster), was fed with 50 ,llc of 4CO2. Twenty-four hours before the '4CO2 was supplied the shoots were treated as follows. An upper leaf was fed "CO2 with (a) shoot darkened below fed leaf; (b) shoot defoliated below fed leaf; (c) shoot decapitated above fed leaf; or (...

Effect of shade stress on growth, morphology, and carbon dynamics of loblolly pine branches

“…Quinlan and Weaver (1970) found that downward movement of photosynthate in Vitis vinifera L. could be reversed by darkening the upper portion of the shoot. Thrower and Thrower (1980) Schneider and Eschrich 1985).…”

Retranslocation of carbon reserves from the woody storage tissues into the fruit as a response to defoliation stress during the ripening period in Vitis vinifera L.

“…While the relationships between photoassimilated carbon and carbon supply to the fruit have been extensively studied in grapevines (Hale and Weaver 1962;Koblet 1969Koblet , 1975Quinlan and Weaver 1970;Koblet and Perret 1972, 1979, 1982Stoev and Ivantchev 1977;Hunter and Visser 1988a, b;Motomura 1981Motomura , 1990), information on the retranslocation of carbohydrates stored in the permanent structure of the vine is limited to the fate of the carbon reserves accumulated in the previous growing season. Scholefield et al (1978), Hori (1979, 1980) and studied the contribution of assimilates accumulated in the previous (long-term reserves) and current season (daily reserves) to early shoot growth of grapevine.…”

Alocação de fotoassimilados marcados e relação fonte-dreno em figueiras cv. Roxo de Valinhos. 2. Tempo de alocação

“…2. Allocation time partições apicais no menor tempo estudado (Quinlan & Weaver, 1970;Quinlan & Preston, 1971;Simkhada et al, 2007).…”