Ecotypic Variation in Photosynthesis, Stomatal Conductance, and Water Use Efficiency of Illicium lanceolatum in Response to Light Intensity Under Drought and Recovery

Increasingly frequent extreme droughts threaten forest vegetation and highlight the need to identify drought-tolerant germplasm. To support conservation and cultivation of <i>Illicium lanceolatum</i>, we investigated ecotypic differences in photosynthetic responses to short-term drought and rewatering under varying light intensity. One-year-old seedlings from four <i>I. lanceolatum</i> ecotypes originating from the Zhejiang (Lin'an, LA; Kaihua, KH), Jiangxi (Wu'ning, WN), and Fujian (Nan'ping, NP) provinces in China were subjected to drought stress by withholding irrigation and subsequent rewatering. Photosynthesis-light response curves were measured before drought; 2, 4, and 7 days after the last watering; and following rewatering. Short-term drought significantly affected photosynthetic traits in an ecotype-dependent manner. Maximum net photosynthetic rate, light saturation point, light compensation point, and apparent quantum yield increased during drought, indicating enhanced utilization of both high and low light. After rewatering, stomatal conductance increased significantly in the WN and KH ecotypes but declined in the NP ecotype when compared with those under the initial water supply. Instantaneous water use efficiency (A/E) recovered rapidly in all ecotypes and exceeded pre-drought levels. Under light intensity above 1500 µmol·m^-2·s^-1, stomatal conductance exhibited a significant nonlinear relationship with water use efficiency. Overall, these physiological responses indicate that <i>I. lanceolatum</i> is moderately drought-tolerant and exhibits mild sensitivity to soil water variation. The WN and KH ecotypes showed superior improvement in water use efficiency under drought and high light, suggesting their potential for breeding drought-resistant cultivars and for afforestation in drought-prone environments.