Cuttings of cucumber (Cucumis sativus L.) grafted onto squash (Cucurbita moschata Duch.) rootstock using a hole-insertion graft were warmed at the hypocotyl of the rootstock in a cold chamber for acclimatization: they were soaked in water held at 31°C from the basal cut-end to the graft union at an air temperature of 12°C for 2 days. Warmed cuttings were planted and grown in an acclimatization chamber for 5 days. Control cuttings were planted immediately after grafting and grown in the chamber for 7 days. The fresh weight of the control scions decreased 2 days after grafting as a result of reduced water content, but that of warmed scions did not decrease. The fresh and dry weight of the warmed scions was 2.2 and 1.6 times that of the control, respectively, at 7 days after grafting. The graft development of warmed and control cuttings, evaluated based on the tensile strength, improved to a similar degree. The leaf conductance and chlorophyll fluorescence ratio (Fv/Fm) of the warmed scions, both of which indicate the degree of water stress, improved compared to those of the control at 7 days. These results demonstrate that the warming treatment does not adversely affect graft development but does reduce water stress at low air temperature during early acclimatization, and therefore improves early growth.
2010 by Japanese Society for Horticultural Science