Structural and hydraulic changes in grape shoot xylem under different root zone volumes

Root zone restriction, an efficient cultivation technique in grape production, alters the morphology and function of both the root system and the above-ground parts. The xylem serves as a crucial conduit connecting the root system to the above-ground structures, facilitating the transport of water and nutrients. However, there is currently limited research on how root zone restriction affects the structure and function of the xylem. In this study, two-year-old 'Shine Muscat' grapevines were planted in six containers of varying volumes to investigate the growth and anatomical structure of their shoots, particularly focusing on vessel structure and hydraulic conductivity in the shoots’ xylem. The results indicate that a decrease in container volume leads to a decrease in shoot growth and xylem vessel size. Changes in root zone volume significantly affected the water conduction in the upper shoots. The isolation of xylem vessel elements revealed that a reduction in root volume decreased the proportion of wider vessel elements (d > 150 μm) and those with single perforation plates, but increased the inclination angle of the end walls of the vessel elements. Consequently, the restriction of root zone volume resulted in longer and narrower vessels in the shoots, a decrease in ratio of the single perforation plates, and an increase in the end wall tilt angle. These structural changes heightened transport resistance and consequently inhibited shoot growth. This study elucidated how root zone volume influences the growth of grape shoots in terms of changes to the structure of xylem vessels, thereby opening up new avenues for the management of grape cultivation.