Abstract:

Cunninghamia lanceolata is one of the most important coniferous species in southern China, but its high sensitivity to drought restricts its expansion. Understanding the intraspecific variation of physiological responses to drought can help us manage this plantation better.

We selected 3-year-old seedlings of C. lanceolata, which originated from the low precipitation (LP), middle precipitation (MP) and high precipitation (HP) habitats, respectively. Seedlings were grown under drought stress (20% of soil volumetric water content) for 40 days. The ecophysiological responses and adaptive strategies with different drought tolerance were investigated.

LP provenance possessed the best tolerance to drought stress, suggesting that considerably increased carbohydrates and nitrogen-containing compounds as osmotic protective materials, which were driven by fast carbon and nitrogen metabolisms. In addition, the highest peroxidase activity could effectively eliminate hydrogen peroxide in drought-stressed LP provenance. The MP provenance reserved a large amount of non-structural carbohydrates, which may act as a certain buffer for encountering drought stress. Importantly, timely closure of stomata to reduce needle transpiration when encountering a water deficiency would help them adapt to long-term drought. MP provenance adopted a conservative water-saving strategy. However, HP provenance regulated root growth (increased root/shoot ratio) and reduced penetration potential to help them absorb water. The different strategies among provenances may be related to the long-term domestication of the geographical environments. Therefore, our results underline the importance of provenance-specific responses to drought stress. It is highly significant to accelerate the selection of drought-resistant germplasms and to cultivate high-yield plantations in the future.

Key words: Chinese fir, drought, physiology, provenance-specific, antioxidants, carbon and nitrogen metabolisms