Crescimento e trocas gasosas de copo-de-leite em função de graus-dia de desenvolvimento

Abstract

The calla lily (Zantedeschia aethiopica) is an ornamental plant with growing acceptance in the Brazilian market, and present thermal restrictions for its cultivation. The objective was to study its biological cycle in degree-days development (GDD) to characterize the best time for planting and vegetable production. Rhizomes were planted individually in the autumn and winter, in pots and kept in a greenhouse. Monthly, phytotechnical characteristics and gas exchange rates were evaluated. The results were submitted to regression analysis and the curves had sigmoidal fit, polynomial or exponential. Seedlings planted in the autumn showed greater development of the shoot, root and floral stem production, staying longer in the vegetative phase before to start flowering and reaching lower GDD. While the seedlings planted in winter suffered early maturation to accumulate higher GDD and lower floral stem production. Calla lily seedlings planted in autumn showed: higher efficiency of water use, more efficiency light use, the greater rate of net photosynthesis and higher density of active photosynthetic photon flux. The winter planting had higher transpiration rate due a higher temperature values of GDD. Being able to characterize the development stages according to gas exchange. The calla lily needs to be cultivated with irradiance between 250-450 µmol m-2s-1, temperatures between 25-30 °C in the initial growth phase until achieve 1000 GDD, followed reduction of the temperature between 10-15 °C until achieve 3500 GDD enabling higher floral stem production.