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

During the prebloom and bloom stages, no movement of labeled photosynthates occurred from a shoot of Vitis vinifera L. fed with (14)CO(2), 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 10(-3)m gibberellic acid during the prebloom stage. During the bloom stage darkening or defoliation of the unfed shoot resulted in the import of labeled photosynthates from the adjacent fed shoot. Similarly, movement of (14)C into an untreated shoot was induced by removing the terminal 7.5 centimeters and deblossoming the fed shoot. During the berry set stage, translocation of labeled photosynthates from a newly exporting leaf was upwards to the shoot tip, but the direction of movement was reversed by removal of the shoot tip or by darkening or removal of the leaves below the fed leaf. Translocation of photosynthates was predominantly basipetal from a fed leaf near the base of the shoot during the berry set stage, but upward movement was induced by darkening or defoliation of the upper part of the shoot.