PJB-2018-1716
Effects of different nitrogen forms on the nitrogen distribution and utilization of Tamarix ramosissima seedlings under water stress
Haohao Lv, Xiaodong Ma, Ruiqun Zhang, Xiaoli Zhong, Chengang Zhu and Yuhui Yang
Abstract
In order to explore the influence of drought stress and nitrogen supplementation on changes in growth, photosynthetic physiological traits, and nitrogen distribution and utilization in Tamarix ramosissima seedlings, four soil watering regimes (D1-20%, D2-35%, D3-50%, and D4-75% of relative field capacity) and supplementation with two nitrogen forms (15N-KNO3 and 15N-NH4Cl) were evaluated. The results indicated that 1) water was the main factor influencing seedling growth. 15N-NH4Cl was more easily absorbed by the roots for total biomass accumulation, while 15N-KNO3 absorption for total biomass accumulationwas promoted under D4. Under water deficient conditions, 15N-KNO3 increased the root/shoot ratio significantly, and this ratio was significantly increased by 15N-NH4Cl under D3. 2) The two different nitrogen forms significantly influenced the chlorophyll a content when the seedlings were subjected to severe water stress, while 15N-NH4Cl had a significant effect on the chlorophyll b content under D2 and D3. Nitrogen improved the photosystem (PS) II actual photochemical efficiency (φPS(II)) of the seedlings, with 15N-NH4Cl significantly effecting φPS(II) under D1 and D3, and 15N-KNO3 being more influential under D2. 3) The nitrogen absorption capacity was diminished under D1 and D4, and followed a trend of an initial increase followed by a decrease along with the increase in soil moisture. The distribution of 15N-KNO3 to the seedlings was higher in comparison to 15N-NH4Cl, whereas the utilization of 15N-NH4Cl was higher. The interactive effects of water and nitrogen thus influence the ability of seedlings to adapt to undesirable surroundings.
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