关键词: 桑树, NaCl和Na2CO3胁迫, 光合特性

Abstract: Taking 1-year old Morus alba variety ‘Qinglong’ seedlings as test materials, this paper studied their
 growth and photosynthetic characteristics under the stresses of different concentration neutral salt NaCl and alkali salt Na2CO3. Salt stresses decreased the plant height and the leaf number, biomass, and photosynthetic capacity of the seedlings markedly. With increasing concentration Na+, the leaf stomatal conductance, transpiration rate, net photosynthetic rate, actual photochemical efficiency, electron transport rate, and photochemical quenching (qP) decreased obviously, the energy dissipation rate increased, and the light use efficiency and photosynthetic capacity dropped down. At low concentrations Na+〖KG*5〗(＜150 mmol·L-1), the seedlings growth and leaf photosynthetic capacity were slightly inhibited, and the adaptability of the seedlings to the salt stresses increased via the increase of root/shoot ratio. However, this protection mechanism was impaired by increasing salt concentration. Na2CO3 stress (Na+ concentration＞50 mmol·L-1) had stronger inhibitory effects on the seedlings growth and leaf photosynthetic capacity, and the effect increased with increasing Na+ concentration. It was concluded that at Na+ concentration ＜150 mmol·L-1, the photosynthetic adaptability of M. alba to neutral salt stress was mainly dependent on the plant morphology and photosynthetic metabolism, but at Na+ concentration ＞150 mmol·L-1, the photosynthetic adaptability of M. alba to alkali salt stress was mainly dependent on the photosynthetic metabolism.

Key words: Morus alba, NaCl and Na2CO3 stresses, photosynthetic characteristics