PHOTOSYNTHETIC-LIGHT RESPONSE CURVE OF FOUR HEMP (Cannabis sativa L.) VARIETIES AT VEGETATIVE STAGE
Light energy is an important driving force of photosynthesis in plants. The objective of the current experiment was to determine the light requirement for maximal photosynthesis in hemp (Cannabis sativa L.). Researchers examined the response of photosynthesis under thirteen different levels of light intensity (PPF) from 0–2000 mmolPPF m-2 s-1 of four hemp varieties including Auto Blues (Sandy), Sour RNA Seedless, Early Remedy, and Sour Suver Haze Seedless] at vegetative stage. The result showed that net photosynthetic rate (A) rapidly increased in response to increasing PPF range of 0–1000 mmolPPF m-2 s-1, then slightly increased based on increasing PPF. The maximum gross photosynthetic rates (Amax) among four hemp varieties were in the range of 36.8–44.2 mmolCO2 m-2 s-1. The light saturation points (Is) where the A reached their maximum ranged between 916.9–1030.2 mmolPPF m-2 s-1 and the light compensation points (Ic) ranged between 77.0–99.0 mmolPPF m-2 s-1. The maximum photorespiration rates (Rl max) were in the range of 7.9–11.6 mmolCO2 m-2 s-1. The light requirement data from this study could be used for light management in hemp cultivation.
