The seasonal dynamics of bud dormancy in grapevine suggest a regulated checkpoint prior to acclimation

ABSTRACTGrapevine (Vitis vinifera L.) displays wide plasticity to climate and seasonality, ranging from strongly deciduous to evergreen. Understanding the physiology of decisions to grow or quiesce is critical for improved crop management, prediction, and the adaptability of production to alternative climate scenarios. The perenniating bud (N+2) is a major economic unit and focus of study. Here we investigated the physiology and transcriptome of cv. Merlot buds grown in a temperate maritime climate from summer to spring in two consecutive years. The changes in bud respiration, hydration and internal tissue oxygen data were consistent with the transcriptome data. ABA-responsive gene processes prevailed upon the transition to a deep metabolic and cellular quiescence in the bud during autumn. Light, together with hypoxia and redox signalling presided over the resumption of nuclear and cellular growth in the transition to spring. Comparisons with transcriptome data from bud burst studies revealed a number of regulatory candidates for the orderly resumption of growth in spring, including components that may integrate light and temperature signalling. Importantly however, the bud burst forcing data, which is widely used as a measure of bud dormancy, were not consistent with the physiological and transcription data. We hypothesise the existence of a physiological checkpoint following bud set in summer, which if not met results in extreme quiescence. Collectively this is the most integrated developmental dataset of the latent bud of cultivated grapevine, and establishes a platform for systems approaches to study seasonal plasticity.One sentence summaryPhysiology and transcriptome data provide strong evidence of a regulatory checkpoint prior to acclimation and dormancy in latent grapevine buds.

POTTED MINIATURE ROSE LONGEVITY AFFECTED BY FLOWER RESPIRATION

Five cultivars of potted miniature roses (`Candy Sunblaze', `Lady Sunblaze', `Orange Sunblaze', `Red Sunblaze' and `Royal Sunblaze') were grown until stage 1 (bud showing color with sepals starting to unfold). At this stage one half of the plants were moved to interior conditions (12 μmol s-1 m-2 from cool white fluorescent lights for 12 hr daily and 21 ± 1C) and the other half were maintained in the greenhouse at recommended production conditions. Stage 1 bud respiration, flower respiration at flowering and at 2, 4, 6 and 8 days after flowering were assessed for plants in the greenhouse and under interior conditions. Also, flower interior longevity was assessed for all the cultivars and the correlations between flower longevity and flower respiration at the different stages were analyzed. At flowering and under interior conditions `Red Sunblaze' lasted the longest (23 days) followed by `Orange Sunblaze' (18 days), `Lady Sunblaze' and `Candy Sunblaze' (16 days), and `Royal Sunblaze' (13 days) and flower respiration was 2.08, 2.74, 3.91, 3.59 and 3.94 mg CO2 g-1 hr-1, respectively. In miniature rose, flower longevity was negatively correlated with flower respiration rate (P = 0.01).

Chemical and Physical Effects of the Accumulation of Glyphosate in Common Milkweed (Asclepias syriaca) Root Buds

Distribution of14C-glyphosate [N-(phosphonomethyl)glycine] in chemically treated and physically manipulated common milkweed [Asclepias syriaca(L.) ♯ ASCSY] was studied in greenhouse and growth chamber experiments. Pretreatment with glyphosate at 0.6 and 1.1 kg ae/ha 3 days prior to14C-glyphosate application to leaves reduced the concentration of14C recovered from shoots and leaves above the14C-glyphosate-treated leaves but had no influence on the concentration of14C in proximal root buds. Partial removal of the shoot and root prior to the application of14C-glyphosate increased bud respiration and the concentration of14C in the proximal root buds. Proximal root buds treated with 1 mM of 6-benzyl-aminopurine (BAP) for 6 days (3 days prior to application of14C-glyphosate) contained seven times more14C/mg than root buds of BAP-untreated plants, suggesting that dormant buds could be chemically stimulated to accumulate higher concentrations of glyphosate. BAP-treated buds were killed by foliar applications of glyphosate at 1.1 kg/ha, indicating that proximal root buds can be stimulated to acquire lethal concentrations of glyphosate.