不同盐胁迫对柳枝稷生物量、品质和光合生理的影响

为明确不同盐胁迫对柳枝稷生物量、品质及光合生理的影响,以无盐胁迫作为对照(CK),选取0.40%Na Cl、0.80%Na2SO4和0.80%Na HCO3进行了土柱试验。结果表明:(1)与CK相比,Na Cl、Na2SO4、Na HCO3胁迫下柳枝稷地上生物量、地下生物量、总生物量、籽粒产量及根冠比均显著降低(P0.05),总生物量分别降低49.39%、60.52%、76.45%,Na HCO3对柳枝稷的生长抑制作用最强,Na Cl最弱;(2)Na Cl胁迫下柳枝稷地上生物质灰分含量显著增高14.89%,Na2SO4胁迫下硫(S)含量显著增高262.32%,纤维素含量显著降低13.71%,Na HCO3胁迫下钾(K)含量显著增高54.95%,半纤维素含量显著增高10.87%,灰分和S含量的增高不利于柳枝稷地上生物质的燃烧利用,纤维素含量的降低和半纤维素含量的增高不利于其转化利用;(3)Na Cl、Na2SO4、Na HCO3胁迫下柳枝稷叶片净光合速率(Pn)分别显著降低21.89%、29.54%和24.59%,气孔限制因素可能是其光合作用受到抑制、生物量下降的关键因素。

Effects of salt stress on biomass, quality, and photosynthetic physiology in switchgrass

In order to study the effects of salt stress on biomass, quality, and photosynthetic characteristics in switchgrass, a soil column test was performed with different salt stresses: 0.40% NaCl, 0.80% Na₂SO₄, and 0.80% NaHCO₃ (critical lethal concentration). Switchgrass with no salt stress served as control (CK). The results obtained are as follows: (1) The aboveground biomass, underground biomass, total biomass, seed yield, and root cap ratio of switchgrass decreased significantly (P < 0.05) under salt stresses of 0.40% NaCl, 0.80% Na₂SO₄, and 0.80% NaHCO₃ compared to the CK. Aboveground biomass of switchgrass was 56.14%, 61.73%, and 76.90% lower than the CK, respectively;underground biomass was 36.12%, 58.67%, and 77.57% lower than the CK;total biomass was 49.39%, 60.52%, and 76.45% lower than the CK;seed yields were 70.95%, 52.88%, and 33.81% lower than the CK;and the root cap ratios were 25.00%, 31.25%, and 32.50% lower than the CK. The relative seed mass of switchgrass was 0.92%, 1.91%, and 4.50% of the control under 0.40% NaCl, 0.80% Na₂SO₄, and 0.80% NaHCO₃, respectively. Large differences were observed among salt stresses in the degree to which growth was inhibited, although all were under critical lethal concentrations. Salt stress with 0.80% NaHCO₃ caused the most serious negative impact on switchgrass biomass, and the weakest was with 0.40% NaCl. Biomass distribution between vegetative parts and sexual organs varied greatly with salt stress. (2) Grown with 0.40% NaCl, the ash content of aboveground biomass increased 14.89% compared to the CK. Grown with 0.80% Na₂SO₄, the sulfur (S) content of aboveground biomass increased 262.32% and cellulose content decreased 13.71%. With 0.80% NaHCO₃, potassium (K) content increased 54.95% and hemicellulose content increased 10.87%. All five of these differences were statistically significant. Other quality indexes showed no significant differences, either among salt stresses or in comparison to CK values. The increased ash content and S content observed under 0.40% NaCl and 0.80% Na₂SO₄ negatively affected the biomass combustion quality. The reduction in cellulose content and increase in hemicellulose content rendered the transformation and utilization of switchgrass biomass more difficult. (3) Grown with 0.40% NaCl, 0.80% Na₂SO₄, and 0.80% NaHCO₃, the net photosynthetic rate (Pn) and the maximum photosynthetic rate (Pmax) of switchgrass leaves was inhibited significantly compared to the CK. Pn decreased 21.89%, 29.54%, and 24.59%, respectively, and P_max decreased 14.52%, 10.00%, and 4.1%, respectively. Stomatal conductance (Gs), intercellular CO₂ concentration (Ci), transpiration rate (Tr), light saturation point (LSP), and instantaneous light energy utilization efficiency (SUE) all decreased significantly compared to the CK. The limiting value of stomata (Ls) increased 20.27%, 16.22%, and 16.22%, respectively. The apparent quanta efficiency (AQY), respiration rate (Rd), instantaneous carboxylation efficiency (CUE), light compensation point (LCP), and water use efficiency (WUE) showed different magnitudes of change under different salt stresses. Stoma limitation may be the key factor inhibiting the photosynthesis and growth of switchgrass. This study lays a solid foundation for the large-scale planting of switchgrass in saline marginal land in northern and northwestern China.