Spring root-zone temperature regulates root growth, nutrient uptake and shoot growth dynamics in grapevines

Background and Aims: Environmental factors such as root-zone temperature can influence plant development. Linkages between spring soil temperature, carbohydrate reserve mobilisation, nutrient uptake and nitrogen partitioning were investigated in Shiraz grapevines to gain better understanding of how this abiotic factor can alter root and canopy development. Methods and Results: Plants were exposed to a cool, an ambient or a warm root-zone temperature over a 9-week period from budburst. Root starch mobilisation was correlated to the sum of cumulative heat units absorbed by the soil (soil growing degree days, GDDsoil) and this contributed to greater fine root density and extent of root branching. Most macronutrients, including N, accumulated to greater concentration in the leaves of vines exposed to the warm root-zones. Patterns of 15N accumulation indicated that despite greater fertiliser-N uptake in the warm root-zone treatment, most of the N that accumulated in the shoots was the result of N reserve mobilisation. Warmed root-zones resulted in plants with accelerated leaf emergence, extended internodes and elongated shoots with larger leaves. Plant leaf area and shoot dry mass were both positively correlated to GDDsoil, but inversely correlated to root starch concentration, indicating a link between root carbohydrate reserve mobilisation and shoot growth. Conclusions: Warm soils stimulated root starch and N mobilisation, root growth and primary nutrient uptake with further consequences on canopy growth and altered N partitioning among the plant components. Significance of the Study: Following winter dormancy, GDDsoil can thus be used to model above- and below-ground plant growth responses in the grapevine.