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

Abstract

Net CO2 assimilation rate (A), stomatal conductance (g,), and weight per unit leaf area (W) were determined on Thompson Seedless grapevines grown in the field. Treatments included fruit set applications of gibberellic acid (40 milligrams gibberellic acid (GA3) per liter) to vines, shoots and clusters, alone and in combination with trunk girdling. Leaf A and g, were measured prior to and 3, 6, and 13 days after fruit set. Weight per unit leaf area was determined on leaves collected subsequent to gas exchange measurements. Leaf A of girdled vines was reduced approximately 30% when compared to the control 13 days after treatment. The reduction in A due to girdling was not as great when vines were sprayed with GA3. GA3 sprays alone had no significant effect on A. Stomatal conductance was reduced by girdling 13 days after treatment. Weight per unit leaf area was 17% greater for trunk girdled vines when compared to the controls. Results indicate GA3 affected net CO2 assimilation rate only on girdled vines, a treatment which increased weight per unit leaf area.Trunk girdling and GA3 applications long have been used commercially to increase the weight of seedless grapes (4,17). 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) (2,8,14). The accumulation of carbohydrates above the girdle (5, 18) also has been implicated in reducing leaf net CO2 assimilation rate of grapevines (5). 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), however, conflicting reports have been published on the effect of GA3 on A of bean plants (1, 9). 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).There is no information as to the effect of a combination of GA3 and girdling on grapevine leaf net CO2 assimilation despite their combined use to increase berry weight. The objectives of this study were to determine the effects of girdling, GA3 application, and a combination of both practices on leaf A, stomatal conductance (g), and weight per unit leaf area of Thompson Seedless grapevines in a field situation. This grape cultivar was chosen since its berry weight consistently has been increased by GA3 applications and girdling (4, 17). MATERIALS AND METHODSVitis vinifera L. (cv Thompson Seedless) grapevines used in this study were 16-year-old vines grown at the University of California, Kearney Agricultural Center near Fresno, CA. Pretreatment cultural practices consisted of an application of GA3 (Pro-Gibb 2%, containing 16 g GA3/L, Abbott L...

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

“…The magnitude of differences in leaf TNC concentration among treatments were similar to differences in weight per unit leaf area measured in a previous study (8). One (2) with broadbean and may indicate the involvement of GA3 in sugar translocation.…”

“…Other information as given in Figure 1 and Table 1. previous experiment conducted on field-grown vines (8). The effects of the four treatments on leafA were opposite to their effects on leafTNC during that time period.…”

“…GA3 also has been shown to reverse the effect of applied ABA (13) and water stressed (1) induced stomatal closure of grapevine and lettuce leaves, respectively. This study was undertaken to extend preliminary results obtained earlier examining the combined effect of girdling and GA3 sprays on leaf A2 of field-grown grapevines (8) Transient measurements of A, taken on individual, fully expanded leaves from the top of the canopy, were conducted as previously described (26). The relationship between A and ci was determined in an open system similar to that described by Williams (25).…”

“…These types of results indicate that the grapevine would be an excellent system in which to study the effects of source/sink ' alterations on the physiological processes responsible for subsequent changes that occur to the harvestable crop. Girdling has been shown to decrease net CO2 assimilation rate and stomatal conductance of grapevine leaves (6, 8, 10, 1 1). In addition, girdling grapevines results in both an increase in carbohydrate concentration above the girdle (23) and an increase in weight per unit leaf area (8) and ABA concentration in the leaves (6). The depressing effect of ABA on stomatal aperature is well known (18), however, ABA also may affect other processes within the leafassociated with C02 assimilation (4,22).…”

Effects of cane girdling on yield, fruit quality and maturation of (Vitis vinifera L.) cv. Flame Seedless

“…According to the TSS values, it was observed that girdling treatments accelerates ripening. Our results are in agreement with the findings of [17,[24][25][26][27][28].…”