EFFECTS OF LOW-TEMPERATURE ON THE GROWTH OF BLACK-CURRANT CULTIVARS

The effects of prolonged exposure to low temperature above freezing at the onset of growth of three blackcurrant (Ribes nigrum L.) cultivars were examined by growing plants at 5-degrees-C and 12-degrees-C for 7 weeks. Those growing at 5-degrees-C had reduced rates of both leaf ap pearance and leaf expansion. In the cultivar 'Ben More', low temperatu re also delayed bud break by 33 days. Base temperature for leaf appear ance and growth differed, and was lower in the chilling-tolerant culti var 'Ben Lomond' than the chilling-sensitive cultivars 'Baldwin' and ' Ben More'. Low temperature reduced stomatal conductance in 'Ben Lomond ' but not in 'Baldwin'. Photo-inhibition was greater in leaves of plan ts grown at 5-degrees-C than at 12-degrees-C, but the effect of low te mperature did not differ between cultivars. Photosynthetic rate, measu red at 15-degrees-C and 5% CO2, was unaffected by the temperature at w hich plants were grown.