Response of photosynthesis and carbon/nitrogen metabolism to drought stress in Chinese chestnut 'Yanshanzaofeng' seedlings

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Drought is a main factor affecting the growth and yield of Chinese chestnut trees in Yan-shan Mountains. To investigate the responses of chestnut seedlings to drought stress, the growth and physiological indices, including photosynthetic characteristics, biomass, proline, malondialdehyde, carbon and nitrogen contents were measured in roots, stems, and leaves after the Chinese chestnut 'Yanshanzaofeng' seedlings in the pots were treated by simulating drought for 22 days. The results showed that, compared with the normal irrigation, water contents in the roots, stems and leaves were decreased by 18.3%, 29.0% and 62.8%, respectively, accompanied by the considerable increases in the contents of proline (355.0%-1586.7%) and malondialdehyde except in the stems (41.1%-81.3%). The non-photochemical quenching coefficiency and net photosynthetic rate in the leaves were significantly decreased by 49.4% and 77.4%, respectively. The contents of non-structural carbohydrates were increased by 21.4% in stems and 69.5% in leaves, but that in roots did not change. The contents of nitrate were increased by 28.9% in stems and 26.8% in leaves, but that in roots did not change. Ammonium nitrogen was increased by 16.2%, 12.9% and 217.6% in roots, stems, and leaves, but being statistically significant in the leaves. These results indicated that drought stress led to serious damage to 'Yanshanzaofeng' chestnut seedlings, which inhibited photosynthetic performance, but they could improve their adaptation to drought stress by enhancing carbon and nitrogen metabolism. Our results provide a reference for the breeding and cultivation of drought resistance of the local Chinese chestnut resources.