Growth Regulator Induced Movement of Photosynthetic Products Into Fruits of `Black Corinth' Grapes

Abstract

A bstract. The effect of exogenous growth regulators on movement of assimilates into flowers and young fruits of 'Black Corinth' grapes was studied. Clusters were treated with growth regulator and after 0.5 hr to 5 davs the leaves above the clusters were exposed to 14CO. Control shoots received 14CO9 but no growth regulator. At harvest, counting and radioautographic techniques were used to ascertain amount and distribution of activity in clusters. Clusters were dipped in 4-CPA (4-chlorophenoxyacetic acid), GA3 (gibberellic acid), or BA (benzyladenine). All berries were heavier than controls within 3 days. Total counts in the fruits were increased by 4-CPA, and the distribution of radioactivity among the sugar, organic acid, and amino acid fractions was usually altered by all treatments. In a time series experiment, within 6 hr after treatment of fruits with GA3 there was almost an 8-fold increase in total counts relative to the control. After 12 hr there was about a 9-fold and 6-fold increase in counts in tartaric and malic acids, respectively, and in y-aminobutyric acid, pipecolic acid, and valine increases of 56, 150, and 330 ters at the late bloom or early fruit-set stage were used. One cluster per shoot was retained and all clusters were trimmed to about the same size. Clusters or portions of clusters were dipped momentarilv in soluitions of 6 X 10-5 M gibberellic acid (GA3), 1.3 X 10-4 M of the auxin 4-chlorophenoxyacetic acid (4-CPA), or 8.9 X 10-3 M of the cytokinin benzvladenine (BA), using B-1956 at 0.05 % as a wetting agent. These concentrations of growth regulators were utilized because they had been previously shown to cause a large increase in size of 'Black Corinth' flowers and fruits (16,18,19). Two shoots were utilized per vine, and in all instances the same treatment was made to these 2 shoots on a given vine. Previous research revealed there is little or no movement of growth regulator out of a cluster, as they are importing photosynthate and olher compounds (17,18). Treatments were made between 8:00 and 9:00 AM. After a time interval ranging from 0.5 hr to 5 days the leaf immediately ibove and on the same side of the stem as the cluster was treated with 14CO2 for 30 min. A plastic bag was placed around the leaf to be treated.

Net CO2 Assimilation Rate of Grapevine Leaves in Response to Trunk Girdling and Gibberellic Acid Application

“…It has been shown that GA3 may enhance the export of leaf carbohydrates in grape (20). The greatest increase of W in this study was due to girdling, with smaller increases when girdled vines were sprayed with GA3.…”

“…GA3 application has been shown to change assimilate distribution in kikuyu grass (7). Cluster or vine GA3 sprays also increased the amount ofassimilates directed into the fruit of Black Corinth grapevines, from the leaf above the cluster (20).…”

“…The association between A2 and carbohydrate level is not unique to grapevines, and has been shown in numerous plants when girdled (5,15). GA3 sprays have been shown to increase A of several species (7,16,20) GA3 on A of bean plants (1,9). GA3 application has been shown to change assimilate distribution in kikuyu grass (7).…”

“…Presently both practices are used in conjunction with one another as their effects have been shown to be synergistic on increasing berry weight (17). It also has been shown these cultural practices affect net CO2 assimilation rate (3,5,8,16), stomatal conductance (2,3), and carbohydrate distribution (7,20) in various plant species including Vitis vinifera. Girdling and GA3 application alters grapevine leaf (2,8), shoot (15) (2,8,14).…”

Effect of plant growth regulators on flower development in the grapevine (Vilis viniferaL.) cv. Cabernet Sauvignon

“…Gibberellins are known to increase the sink capacity in developing flowers of strawberries by increasing cell division and enIargement (Archbold & Dennis 1985) and spraying grape bunches with GA 3 increased the amount of assimilates directed into the fruit from the leaf above the cluster of Black Corinth grapes (Weaver et al 1969). Similareffects have occurred on inflorescences sprayed 2 weeks before full bloom (Motomura 1986).…”