ABA and GA₃ increase carbon allocation in different organs of grapevine plants by inducing accumulation of non‐structural carbohydrates in leaves, enhancement of phloem area and expression of sugar transporters

Abstract

Grape quality for winemaking depends on sugar accumulation and metabolism in berries. Abscisic acid (ABA) and gibberellins (GAs) have been reported to control sugar allocation in economically important crops, although the mechanisms involved are still unknown. The present study tested if ABA and gibberellin A3 (GA3) enhance carbon allocation in fruits of grapevines by modifying phloem loading, phloem area and expression of sugar transporters in leaves and berries. Pot-grown Vitis vinifera cv. Malbec plants were sprayed with ABA and GA3 solutions. The amount of soluble sugars in leaves and berries related to photosynthesis were examined at three points of berry growth: pre-veraison, full veraison and post-veraison. Starch levels and amylase activity in leaves, gene expression of sugar transporters in leaves and berries and phloem anatomy were examined at full veraison. Accumulation of glucose and fructose in berries was hastened in ABA-treated plants at the stage of full veraison, which was correlated with enhancement of Vitis vinifera HEXOSE TRANSPORTER 2 (VvHT2) and Vitis vinifera HEXOSE TRANSPORTER 6 (VvHT6) gene expression, increases of phloem area and sucrose content in leaves. On the other hand, GA3 increased the quantity of photoassimilates delivered to the stem thus increasing xylem growth. In conclusion, stimulation of sugar transport by ABA and GA3 to berries and stems, respectively, was due to build-up of non-structural carbohydrates in leaves, modifications in phloem tissue and modulation in gene expression of sugar transporters.

Transcriptomic study of pedicels from GA3-treated table grape genotypes with different susceptibility to berry drop reveals responses elicited in cell wall yield, primary growth and phenylpropanoids synthesis

“…Researchers have reported the effects of this growth regulator on several tissues and conditions. In pedicel tissue, positive regulation by GA 3 on lignin monomers biosynthesis, cell expansion and xylem development has been detected [8,11,28]. The present study supports these findings in pedicel with the identification of upregulated genes with significant annotations for these processes.…”

“…Reports have indicated several morphological changes that take place in the rachis and pedicel following GA 3 treatment [8,9]. It has been found that GA 3 induces changes in the pedicel by increasing the area of xylem and pith structures [8]. One study proposed that the loss of pedicel flexibility could be one of the main factors underlying berry drop in cv.…”

Sunlight transmitted by colored shade nets on photosynthesis and yield of cucumber

“…Due to the effects in these variables, pearl and aluminized nets were placed second, which transmitted the second largest flows of red light and blue light, respectively. These light levels favored the photosynthesis that led to increase the biomass production, which generally implies a greater area of phloem (BARZEGARGOLCHINI et al, 2017;NAZ et al, 2018) and; consequently, a more efficient transport, and greater reserve capacity of assimilates for later use in the fruit filling (MURCIA et al, 2016). Aspects that were enhanced by enrichment of the environment with diffuse light, spectrally modified by the pearl, aluminized, red and blue nets, and photosynthetically more efficient than direct light due to its greater capacity to penetrate the vegetal canopy (OREN-SHAMIR et al, 2001;ILIĆ & FALLIK, 2017).…”

Relationships between population traits, nonstructural carbohydrates, and elevation in alpine stands of Vaccinium myrtillus

“…The starch pattern was consistent with the decreasing amount of sucrose measured in older individuals, in agreement with a decreased translocating area (i.e., phloem percentage), a morphological trait strictly related to sucrose accumulation in parenchymatic tissues of underground ramets. These findings could also be explained considering that high phloem percentage can be found in plants with high reserve mobilization and high metabolic activity, i.e., due to stress responses, plant age (i.e., young individuals) or plant–plant interactions (Lintunen et al., ; Murcia et al., ; Savage et al., ).…”