Resumen de Do temperature conditions at budburst affect flower number in Vitis vinifera L. cv. Cabernet Sauvignon?
Gregory M. Dunn, Stephen R. Martin
Timing of winter pruning (early July versus mid-August) and the application of hydrogen cyanamide were used to manipulate the time of budburst in a population of spur-pruned, 13-year-old Vitis vinifera L. Cabernet Sauvignon vines grown in central Victoria. Delaying pruning by six weeks delayed budburst by an average of four days. This extended the duration of budburst for the entire population, thus, exposing bursting shoots to a greater range of temperature conditions.
Flowers per inflorescence and bunches per shoot were estimated by destructively sampling 300 inflorescences prior to anthesis from shoots of known bursting date. Pruning time did not significantly affect flowers per inflorescence. However, across the entire population of inflorescences sampled, flowers per inflorescence was weakly correlated with daily maximum air temperature on the day of budburst, daily mean soil temperature on the day of budburst and date of budburst (P < 0.001, Adjusted R2 = 3.6%, 3.7%, 4.5% respectively). Inflorescences had fewer flowers on later-bursting shoots and also as temperatures on the day of budburst increased.
More of the variance in flowers per inflorescence was accounted for by the number of inflorescences on the shoot (P < 0.001, Adj. R2 = 17.4%) and the position of the inflorescence relative to other inflorescences on the same shoot, i.e. lower of two, upper of two or sole (P < 0.001, Adj. R2 = 26.1%). Average flowers per inflorescence declined in the order lower of two > upper of two > sole. The best regression model included the position of the inflorescence relative to other inflorescences on the shoot and the date of budburst (P < 0.001), but this still accounted for only 29.2% of the total variance in flowers per inflorescence.
Mean flowers per inflorescence was significantly (P < 0.05) and substantially (97% for back-transformed means) higher for inflorescences on two-inflorescence shoots than for inflorescences on single inflorescence shoots. This suggests that conditions during the previous spring that favour the initiation of uncommitted inflorescence primordia (i.e. high temperature and adequate light) also pre-condition inflorescences to higher flower numbers.
