Abstract A double cropping system for the grapevine (Vitis vinifera L) has been commercially adopted for use in regions where the tropical climate is characterized by high temperatures and small variations in daylength throughout the year. Under these climatic conditions, the use of hydrogen cyanamide (HC), a compound that breaks bud dormancy, is mandatory to produce homogeneous budbreak. However, it is unknown whether grapevine buds are capable of developing endodormancy (ED) under these climatic conditions. In this study, typical signals of ED, such as the number of nodes per cane, the development of periderm and the thickening of the cell wall of the bud meristematic cells, were analysed in vines of “Italia melhorada” grown in Mossoro, Brazil (5°12′16″S), under a natural (ND) photoperiod (12/12 h), a short-day (SD) photoperiod (10/14 h) and a long-day (LD) photoperiod (14/10 h). The abundance of phytochrome A (VvPHYA) and B (VvPHYB) and FLOWERING LOCUS T (VvFT) transcripts in the leaves and buds was also determined. The results showed a reduced number of nodes per cane and development of the periderm in the shoots of grapevines grown under ND and SD photoperiods. In addition, compared with that under the LD photoperiod, the expression of VvPHYA and VvFT under the ND and SD-photoperiod decreased, and the expression of VvPHYB increased. However, the thickness of the cell wall of the bud meristematic cells increased only in the grapevines exposed to the SD photoperiod. Therefore, we hypothesize that cell wall thickening is a characteristic of ED, while decreased expression of VvPHYA and VvFT and increased expression of VvPHYB are characteristic of quiescence. Consequently, under a tropical conditions, the grapevine buds would be in a quiescent state and not in a dormant state.

中文翻译：

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在热带条件下生长的“Italia melhorada”葡萄藤的芽处于静止状态

摘要 葡萄 (Vitis vinifera L) 的双熟系统已在商业上用于热带气候的特点是全年气温高且日长变化较小的地区。在这些气候条件下，必须使用氰氨化氢 (HC)，一种打破芽休眠的化合物，以产生均匀的芽芽。然而，尚不清楚葡萄芽是否能够在这些气候条件下发展内休眠 (ED)。在这项研究中，在巴西 Mossoro 生长的“Italia melhorada”葡萄藤中分析了 ED 的典型信号，例如每根茎的节数、周皮的发育和芽分生细胞的细胞壁增厚。 5°12′16″S)，在自然 (ND) 光周期 (12/12 h) 下，短日（SD）光周期（10/14 h）和长日（LD）光周期（14/10 h）。还测定了叶和芽中光敏色素 A (VvPHYA) 和 B (VvPHYB) 以及开花位点 T (VvFT) 转录物的丰度。结果表明，在 ND 和 SD 光周期下生长的葡萄藤枝条中，每根茎的节数减少，周皮发育。此外，与LD光周期相比，ND和SD光周期下VvPHYA和VvFT的表达降低，VvPHYB的表达增加。然而，芽分生细胞的细胞壁厚度仅在暴露于 SD 光周期的葡萄中增加。因此，我们假设细胞壁增厚是 ED 的一个特征，而 VvPHYA 和 VvFT 的表达降低和 VvPHYB 的表达增加是静止的特征。因此，在热带条件下，葡萄芽将处于静止状态而不是处于休眠状态。