Renewal of vascular connections between grapevine buds and canes during bud break
Xie, Z., Forney, C.F., Bondada, B. (2018). Renewal of vascular connections between grapevine buds and canes during bud break, 233 331-338. http://dx.doi.org/10.1016/j.scienta.2018.02.019
Plain language summary
Grapevines are responsible for the production of grapes that are eaten fresh, made into wine or dried into raisons. For a grapevine to produce year after year, it must survive the cold of winter. Therefore, in the fall of the year the grapevine transitions from a tender to a cold-hardy state. During this time the canes and buds lose their water and vascular connections between them are lost in order to tolerate the cold. In the spring the vine deacclimates and water flows into the buds to begin growth. We studied the process of bud break by observing the formation of vascular connections using light microscopy, and the transport of water into the buds using dye. During dormancy no vascular tissue (xylem) was observed between the bud and the cane isolating the bud. At the stage of bud swelling in the spring, xylem was observed at the junction of the bud and cane. Water uptake through the xylem increased as bud development progressed. Water transport into the bud increased with bud development. Rebuilding of vascular connections between buds and canes plays an important role in vine bud break and shoot development as temperatures increase in early spring.
© 2018 Elsevier B.V. With the seasonal change from winter to spring, grapevine compound buds break dormancy and start a new annual developmental cycle. The rebuilding of vascular connections between buds and canes is vital to ensure normal development of the bud. We monitored the dynamic development of grapevine buds under natural field conditions, observed vascular connections using light microscopy, and investigated the uptake and transport of water in buds and canes from dormancy to bud break. During dormancy, the bud was isolated from the cane and no xylem was observed in the bud or the junction region between the bud and the cane. However, at the stage of bud swelling (stage II), xylem was observed at the cane to bud junction. The rate of water uptake through the xylem at the junction increased as bud development progressed. These results suggest that buds were hydraulically isolated from the cane during dormancy and the formation of xylem between bud and cane started with swelling of the bud. The velocity of water transport into the bud also increased with bud development. We discuss several factors that affect the formation and differentiation of xylem, including temperature, hormones and water. It is likely that the rebuilding of vascular connections between buds and canes is related to multiple factors rather than any one individual factor.