Effect of Light Intensity on Leaf Morphology, Photosynthetic Capacity, and Chlorophyll Content in Sage (Salvia officinalis L.)

Sage (Salvia officinalis) has been an important medicinal plant since antiquity. Here, we aimed to determine the optimum light intensity for S. officinalis growth by quantifying the effects of different shade treatments on plant morphology, chlorophyll and carotenoid content, and photosynthetic capacity in a semi-arid region of Iran. Plants were grown for 5 months under full sunlight (0% shade) as well as 30%, 50%, or 70% shade levels by applying different shade treatments. While leaf size was greatest under 50% shade level, leaves of seedlings grown under full sunlight were smallest. Leaf color under both 50% and 70% shade levels was yellowish-green. The highest photosynthesis activity was achieved under full sunlight. Decreasing light intensity led to an increase in chlorophyll and carotenoid content. Shade levels above 30% limited carbon assimilation and led to decreased essential oil content and plant growth. In conclusion, 30% shade is suggested to be an optimum light irradiance for the cultivation of S. officinalis.