ACCUMULATED LEAF NUMBER IN STRAWBERRY CULTIVARS GROWN IN A GREENHOUSE

Previous studies have shown that cultivars of the same species respond differently to air temperature through what is referred to as the thermal interval for leaf tip appearance (phyllochron) by showing differences in the rate of appearance of leaves and in the time to the beginning of flowering. This information is important for characterising plant development and for evaluating the growth and adaptation of plants to the environment. Two experiments were conducted to estimate the phyllochron of five strawberry cultivars, ‘Aromas’, ‘Camino Real’, ‘Albion’, ‘Camarosa’ and ‘Ventana’, grown under greenhouse conditions. The study was performed in the agricultural greenhouse at the University of Passo Fundo (28°15’41”S; 52°24’45”W, 709 m a.s.l.) from 8 June to 15 September 2009. This period included the time from planting to the 2^nd flowering. In the first experiment, plants were grown in soil. In the second experiment, they were grown in soilless substrate in white polyethylene bags. The two trials were conducted at the same time. The treat¬ments were arranged in a randomised block design with four replicates. Phyllochron (°C day leaf^-1) was estimated by calculating the inverse of the slope of the linear regression between the number of leaves in the main crown and the accumulated daily thermal units (base temperature = 7°C). There were significant differences among cultivars grown in a soilless system, with higher phyllochron values for ‘Albion’ (199.96±29.7), which required more accumulated degree-days to produce a leaf, whereas ‘Ventana’ (85.76±11.51) had a lower mean value of phyllochron. In the cultivars produced in the soil, significant differences in temperature requirements were found between the cultivars ‘Aromas’ (103.98±13.65) and ‘Ventana’ (60.38±12.49).