The phenological patterns of two populations of Cnidoscolus quercifolius were evaluated in the western Seridó region of Paraiba state, Brazil, from March 2009 to February 2011, with data collected monthly. The evaluations have addressed the quantitative method of analysis that represents the activity indices for both populations growing seasons (fall and sprout) and reproductive (flowering and fruiting), and also studied the intensity index Borchert, who evaluated the flow leaves. The stages were evaluated with respect to variations in rainfall, water potential of plant and quantum efficiency of photosystem II. The bud in the two populations occurred in the late dry season and transition into the rainy season, with peak leafing in January and November 2010 and was negatively correlated with rainfall (rs = -0.54 p <0.05). Leaf fall showed the peak phase in October 2009 and 2010, showing a direct relationship with water potential and photosynthetic quantum efficiency. The flowering and fruiting had greater synchrony in the seasonal rainy period, fruit set was positively correlated with precipitation values during the study period (rs = 0.56 p <0.05). The phenological events of C. quercifolius show marked seasonality in relation to precipitation, water potential and the quantum efficiency of photosystem II.
Euphorbiaceae; phenology; semiarid