In the experiments reported here, single-stem plants of five cultivars were produced from top cuttings, which were collected in the field in May. The cuttings included a portion of the previous years' growth and they were rooted and grown in a peat compost.
On 11 August, the plants were transferred to naturally-lit, controlled environments in Norway, where constant temperatures of 9, 12, 18 and 24 degsC were given. All shoots stopped growing in length within three weeks of the transfer.
Those grown at 12 degsC were longest but the higher temperatures encouraged flowering at more nodes and delayed leaf abscission. The plants then spent some weeks outdoors to "harden off" before being stored at -2 degsC. On 7 April, they were moved to a greenhouse at 15 degsC.
The lowest fruit yields came from plants that had received an autumn temperature of 9 degsC while the highest yields followed autumn temperatures of 12 or 18 degsC. It seems unlikely, therefore, that blackcurrant yields will be adversely affected should autumn temperatures become warmer.
Dr Ken Cockshull, Associate Fellow, Warwick Crop Centre, University of Warwick
Elevated Autumn Temperature Promotes Growth Cessation and Flower Formation in Blackcurrant Cultivars (Ribes nigrum L.) by Sonsteby and Heide (2010). Journal of Horticultural Science & Biotechnology 86 (2): 120-127. The authors' abstract of their manuscript can be seen in full at www.jhortscib.com.