Response of water balance and nitrogen assimilation in cucumber seedlings to CO2 enrichment and salt stress

• DOI: 10.1016/j.plaphy.2019.03.028
• Publication Date: 2019-03-21T20:19:46Z
• Authors: Shuhao Li; Yiman Li; Xinrui He; Qingming Li; Binbin Liu; Xizhen Ai; Dalong Zhang
• Keywords: Cucumis; Nitrogen Assimilation

The effects of CO2 enrichment on water balance and nitrogen (N) assimilation in cucumber (Cucumis sativus L. cv. Jinyou No.35) seedlings under salt stress were investigated. Two-way randomized block design was used: the main treatment consisted of two [CO2] levels, ambient and enriched (400 and 800 ± 40 μmol mol-1, respectively), and the minor treatment consisted on two salinity treatment levels, 0 and 80 mmol L-1 NaCl. The results showed that, under the experimental conditions, enriched [CO2] and salt stress significantly inhibited the N assimilation process in cucumber leaves; however, enriched [CO2] had no effect on the nitrate (NO3-) reduction or ammonium (NH4+) assimilation of leaves under salt stress, inhibiting only the transamination. Moreover, enriched [CO2] increased the plasma membrane H+-ATPase activity, vacuolar membrane H+-ATPase activity and root hydraulic conductivity under salt stress, thereby increasing the ion selective absorption and water absorption capacity. To a certain extent, enriched [CO2] promoted the accumulation of K+ in plants, which significantly reduced the Na+/K+ ratio; moreover, the enrichment ultimately improved the water state conditions and helped to maintain the ion balance in plants under stress, ensuring normal enzymatic activity.