Students investigated the relationship between two environmental factors and the rate of cavitation in a Scots pine tree, Pinus sylvestris, over a 50-hour period. The two factors they investigated were: • photosynthetically active radiation (PAR), which is the light energy available to plants that they absorb and use in photosynthesis • wind speed. The cavitation rate was estimated by recording the number of clicks detected by the sensor. The results are shown in Fig. 3.1. [Figure 3.1]