Flower abscission in Vitis vinifera L. triggered by gibberellic acid and shade discloses differences in the underlying metabolic pathways

Abstract

Understanding abscission is both a biological and an agronomic challenge. Flower abscission induced independently by shade and gibberellic acid (GAc) sprays was monitored in grapevine (Vitis vinifera L.) growing under a soilless greenhouse system during two seasonal growing conditions, in an early and late production cycle. Physiological and metabolic changes triggered by each of the two distinct stimuli were determined. Environmental conditions exerted a significant effect on fruit set as showed by the higher natural drop rate recorded in the late production cycle with respect to the early cycle. Shade and GAc treatments increased the percentage of flower drop compared to the control, and at a similar degree, during the late production cycle. The reduction of leaf gas exchanges under shade conditions was not observed in GAc treated vines. The metabolic profile assessed in samples collected during the late cycle differently affected primary and secondary metabolisms and showed that most of the treatment-resulting variations occurred in opposite trends in inflorescences unbalanced in either hormonal or energy deficit abscission-inducing signals. Particularly concerning carbohydrates metabolism, sucrose, glucose, tricarboxylic acid metabolites and intermediates of the raffinose family oligosaccharides pathway were lower in shaded and higher in GAc samples. Altered oxidative stress remediation mechanisms and indolacetic acid (IAA) concentration were identified as abscission signatures common to both stimuli. According to the global analysis performed, we report that grape flower abscission mechanisms triggered by GAc application and C-starvation are not based on the same metabolic pathways.

Molecular candidates for early-stage flower-to-fruit transition in stenospermocarpic table grape (Vitis vinifera L.) inflorescences ascribed by differential transcriptome and metabolome profiles

“…The gene VvSUC2/SUT2, which participates in phloem or post-phloem unloading, first described as weakly expressed in berries [71], was shown to be involved in onset of berry development. In addition to the known impaired flower formation and berry set resulting from carbon limitation due to inadequate rates of source leaf photosynthesis [9,72], these results indicate the sink strength limitation is an important step during the flower-to-fruit transition stage.…”

Shared and divergent pathways for flower abscission are triggered by gibberellic acid and carbon starvation in seedless Vitis vinifera L

“…Flower abscission can also be boosted by shading conditions (70-90 % light interception) during bloom [ 12 , 31 , 32 ], paving the way to explore light management as an alternative thinning method. The pronounced reduction of net photosynthetic rates under shading promotes the competition for photoassimilates between vegetative and reproductive organs, leading to shedding of the later with less sink strength at this early stage of development [ 33 ].…”

Shade screen increases the vegetative growth but not the production in ‘Fino 49’ lemon trees grafted on Citrus macrophylla and Citrus aurantium L.

“…Thus, the highest CO 2 acquisition in shaded leaves was investment in new vegetative biomass, but not in fruit growth and number. Although further investigation are necessary, this data suggest that shading could also have reduced the fruit number by reducing the flower production and fruit set and/or by enhancing the fruitlet abscission, as reported for 'primosole' mandarin by Germana et al (2001Germana et al ( , 2003 and for Vitis vinivera L. (Domingos et al, 2015); although in other crops as olive (CherbiyHoffmann et al, 2015) and blueberry (Lobos et al, 2013) the return bloom is not affected by shading treatments.…”