Characterization of xylem anatomy and gas exchange traits in selected Croatian grapevine cultivars and wild grapes

Abstract

Grapevine (Vitis vinifera subsp. vinifera L.) is one of the crops most affected by drought, and climate projections indicate that both the frequency and intensity of drought events will increase further in the future. Although grapevine is a Mediterranean plant species with well-developed mechanisms of adaptation to water deficit, including reprogramming of physiological and metabolic processes, osmotic adjustment, and enhanced tolerance to reactive oxygen species, these processes remain insufficiently understood. Although the influence of xylem anatomy on grapevine drought resistance has been documented in some Vitis cultivars, studies are primarily focused on hydraulic vulnerability and embolism resistance; the relationship between xylem structure, transpiration, and stomatal conductance in grapevine remains poorly understood. This study aimed to assess the effects of xylem anatomy on stomatal conductance and transpiration in Croatian grapevine and wild grape genotypes, thereby elucidating the relationship between anatomical traits and physiological responses under drought.

In this research, transpiration rate and stomatal conductance were measured in 13 Croatian grapevine (Vitis vinifera subsp. vinifera L.) and 3 wild grapevine (Vitis vinifera subsp. sylvestris Gmel Heg ) genotypes, comparing control plants with those subjected to a drought treatment. At the same time, xylem structure was analyzed on cross-sections of canes, and pit density and aperture area were measured. Significant differences in xylem anatomy were observed among genotypes. Belina starohrvatska genotype showed the highest pit density (mean = 41.13 pits/mm2), whereas the genotype Plavina exhibited the largest pit aperture area (mean = 0,009 mm2). Treatment effects were significant also for transpiration and stomatal conductance, with a notable genotype × treatment interaction. Post-hoc analyses revealed significant genotype effects on transpiration and stomatal conductance. In Vitis sylvestris genotype Paklenica 120, transpiration averaged 0.871 mmol m⁻² s⁻¹ and stomatal conductance 0.056 mol m⁻² s⁻¹. In genotype Paklenica 122, these values were 0.746 mmol m⁻² s⁻¹ and 0.035 mol m⁻² s⁻¹, respectively.

This study represents the first research on the influence of xylem anatomy on drought-adaptive physiological processes in Croatian grapevine genotypes, particularly wild grapevine. The results may contribute to a better understanding of the mechanisms driving grapevine drought tolerance.