Abstract
At springtime, the formation of stem somatic traits (stem elongation and leaf growth) and reproductive activity (flowering and fruit set) occur simultaneously. They are all competing carbon sinks, with an extremely high demand for carbohydrates. The shoot growth rate is strongly related to environmental temperature, which, according to climate change scenarios, is expected to increase also in extremes. Our hypothesis was that the increase in temperature during budburst could increase the vegetative carbon sink strength reducing the carbon stock available for the reproductive activity jeopardizing flowering of the next year. In our experiment, we artificially conditioned grapevine budburst by exposing the growing shoots to different temperature regimes. Higher temperatures during the spring vegetative growth favored shoot stem extension at the detriment of shoot leaf area. This caused a reduction in vine CO2 assimilation, which, combined with the competition of the growing vegetative organs, affected the concurrent reproductive activity, with carry-over effects on the following year, resulting in a limited flower initiation in dormant buds. These results suggest that the increase in springtime temperature can alter canopy development and vine physiology, resulting in the reduction in reproductive activity with an economical negative impact on grapevine productivity.
Highlights
Shoot growth is related to endogenous and environmental factors; endogenous factors are mainly related to carbohydrate availability, plant water relations, and hormonal signals.Environmental factors are primarily linked to temperature
In T0 treatment, shoot topping was carried out 70 days after budburst (DABB) but did not correspond with the maximum leaf area since shoot topping stimulated lateral shoot growth, which led to the formation of new leaf area
The simulated increase in temperature during and after budburst resulted in an advantage for the elongation of shoot stem, which competes with the formation of leaf area
Summary
Shoot growth is related to endogenous and environmental factors; endogenous factors are mainly related to carbohydrate availability, plant water relations, and hormonal signals.Environmental factors are primarily linked to temperature. Temperature, often indexed as growing degree days (GDD), is the main driver of shoot growth, plastochron, and phenological stages development, when there are no other limiting factors [1,2,3,4]. Shoot growth occurs after budburst in spring and continues until midsummer. During this period, vegetative growth is the most important carbohydrate sink for the formation and development of plant structures, such as leaves, buds, and shoot apex. In the grapevine, young and rapidly expanding leaves are sinks for photosynthates, and they become active carbon exporting organs only when they reach about 30% to 50% of their final size [7]. Shoots become active exporters of carbohydrates before flowering when they reach about six to eight mature leaves [8]
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