模拟大气CO_(2)浓度升高与氮添加对宁夏枸杞生长及光合特性的影响

Effects of elevated CO_(2)concentration and nitrogen addition in simulated atmosphere on growth and photosynthetic characteristics of Lycium barbarum

【目的】探究大气CO_(2)浓度升高与氮添加对宁夏枸杞生长发育特性、光合特性及产量的影响,为更好发掘宁夏枸杞的生产潜力及适应性栽培提供理论参考。【方法】以1年生‘宁杞1号’扦插苗为试验材料,采用开顶气室控制系统设置自然环境CO_(2)浓度[T1,(380±20)μmol/mol)]和升高CO_(2)浓度[T2,(760±20)μmol/mol],设置3个氮添加水平(以每kg土壤施加高氮水溶肥量计)N0(0 g/kg)、N1(0.8 g/kg)和N2(1.6 g/kg),共计6个处理。分别于处理45、60、75、90 d测定‘宁杞1号’株型、光合指标、日均净光合速率及单株产量。【结果】随着CO_(2)与氮素复合处理时间的延长,‘宁杞1号’苗地径、新梢长度和粗度、叶片气孔导度呈增加趋势,气孔限制值呈降低趋势,叶绿素含量呈先升后降再升模式。T2N1处理各时期新梢长度、粗度及叶片胞间CO_(2)浓度较高。T2处理60、75、90 d‘宁杞1号’的净光合速率均显著高于T1处理,其中T2N1处理下‘宁杞1号’净光合速率同比增长87.72%、68.33%、67.56%(P<0.01);CO_(2)浓度升高条件下,N1处理45、60、75、90 d时‘宁杞1号’的蒸腾速率均显著上升(P<0.05),但N2处理45、60 d时‘宁杞1号’的蒸腾速率均显著降低(P<0.05),分别为2.84、2.41 mmol/(m2·s)(P<0.05),N0处理75、90 d时‘宁杞1号’气孔导度显著升高(P<0.05),N1处理75、90 d时‘宁杞1号’的水分利用率显著增加(P<0.05),分别为10.68、9.34 g/kg,但气孔限制值处于较低水平。CO_(2)浓度升高条件下氮素添加降低了气孔限制值与新梢长度、粗度、叶绿素含量及枸杞单株产量的相关性,提高了蒸腾速率、净光合速率、水分利用效率与新梢长度、粗度等株型指标及枸杞单株产量的相关性;根据日均净光合速率模型,CO_(2)浓度升高条件下,‘宁杞1号’理论最佳施氮量为0.875 g/kg(土壤),此时‘宁杞1号’单株产量略高于T1N1处理。【结论】CO_(2)浓度升高条件下,N1处理增加了‘宁杞1号’的地径、新梢粗度,提高了‘宁杞1号’叶绿素含量、净光合速率、气孔导度和水分利用率,降低了其气孔限制值,且N1处理可以保持‘宁杞1号’较高的产量,降低CO_(2)浓度升高带来的负面影响,更适合CO_(2)浓度升高条件下枸杞的种植。

【Objective】This study aims to investigate the effects of various nitrogen treatments on the growth,photosynthesis,and yield of Lycium barbarum under elevated atmospheric CO_(2)concentrations.The objective is to optimize the production and adaptive cultivation of L.barbarum.【Method】One-year-old cuttings of L.barbarum‘Ningqi-1’were used as experimental material.Two CO_(2)concentrations were tested:ambient(T1,(380±20)μmol/mol)and elevated(T2,(760±20)μmol/mol),using an open-top chamber control system.Additionally,three nitrogen levels were applied per kilogram of soil:0 g/kg(N0),0.8 g/kg(N1)and 1.6 g/kg(N2).Measurements of plant morphology,photosynthetic indices,daily net photosynthetic rates,and yield were taken at 45,60,75 and 90 days.【Result】Over time,the combination of elevated CO_(2)and nitrogen treatments enhanced the stem diameter,shoot length,thickness,and stomatal conductance of‘Ningqi-1’,while inhibited the stomatal limit.The chlorophyll content initially increased,then decreased,and later increased again.The T2N1 treatment performs the best during each assessment period.The net photosynthetic rate of“Ningqi-1”treated with T2 for 60,75 and 90 days was significantly higher than that of T1,with increases of 87.72%,68.33%and 67.56%,respectively,reaching rates of 25.24,28.33,and 28.25μmol/(m2·s),respectively(P<0.01).With elevated CO_(2)levels,the transpiration rate of“Ningqi-1”significantly increased during the N1 treatment across 45,60,75,90 days but significantly decreased during the N2 treatment at 45 and 60 days,recording 2.84 and 2.41 mmol/(m2·s),respectively.Additionally,stomatal conductance of“Ningqi-1”significantly increased from 75 to 90 days(P<0.05).Water use efficiency significantly increased from 75 to 90 days post-N1 treatment,reaching 10.68 and 9.34 g/kg,while the stomatal limit remained low.Increasing CO_(2)concentrations reduced the correlation among stomatal limitation and variables such as shoot length,thickness,chlorophyll content,and yield per plant.Conversely,it enhanced the correlation between transpiration rate,net photosynthetic rate,water use efficiency,and the aforementioned plant traits in“Ningqi-1.”Based on the CO_(2)concentration model for daily net photosynthetic rate,the optimal theoretical nitrogen application rate for“Ningqi-1”was estimated at 0.875 g/kg(soil).The yield per plant under this regime was slightly higher than that of the T1N1 treatment.【Conclusion】The N1 nitrogen treatment under elevated CO_(2)conditions effectively increased the stem diameter,shoot thickness,chlorophyll content,net photosynthetic rate,stomatal conductance,and water use efficiency of“Ningqi-1,”while reduced the stomatal limit.This treatment also sustained higher yields and mitigated the adverse effects of increased CO_(2)levels,making it a more suitable option for cultivation in environments with higher CO_(2)concentrations.