根际盐分差异性分布对高粱幼苗生长发育的影响

【目的】盐碱地盐分含量在土壤表层的分布通常是不均匀的,研究不均匀盐胁迫条件下高粱幼苗生长发育和生理生化指标的变化,可为盐碱地高粱栽培和盐碱地高效开发利用提供理论依据。【方法】 利用分根法将高粱根系均匀分成2部分,并分别置于不同浓度（mmol·L ^-1）NaCl中,设置对照为无盐胁迫（记作0/0,下同）、不均匀盐处理（0/200、50/150）和均匀盐处理（100/100）,在人工气候室培养14 d后取样,测量生物量、叶面积、SPAD值、根系形态、渗透调节物质、抗氧化酶活性和光合参数等性状,研究分根盐胁迫条件下高粱生长发育的变化规律。 【结果】 不均匀盐胁迫和均匀盐胁迫均严重影响了高粱幼苗的生长发育,显著降低了高粱幼苗鲜重、干重和叶面积,对叶片的光合能力、抗氧化酶活性和渗透调节物质均有一定程度的影响。然而,不均匀盐处理50/150和0/200的单株干重比均匀盐处理提高了21.19%和62.71%,单株鲜重提高了35.39%和86.44%,叶面积提高了13.22%和88.66%;50/150处理低盐一侧根系鲜重和干重分别是高盐一侧的1.90倍和2.10倍,0/200处理无盐一侧根系鲜重和干重分别是盐胁迫一侧的3.02倍和3.75倍。同样,不均匀盐处理对局部根系形态影响显著,低盐或无盐一侧根系生长明显增加,50/150和0/200处理低盐一侧的根系长度、根系体积、根尖数和分支数显著高于高盐或有盐胁迫一侧根系,进而不均匀盐胁迫条件下整个根系的根系长度、根系体积、根尖数和分支数都高于均匀盐胁迫处理,其中0/200处理的各项指标与均匀盐处理差异均达到显著性水平（P<0.05）。叶片超氧化物歧化酶（SOD）、过氧化氢酶（CAT）和过氧化物酶（POD）活性在不均匀盐胁迫条件下显著升高（P<0.05）;不均匀盐处理的叶片渗透调节性物质脯氨酸（PRO）和可溶性糖（SS）含量显著高于均匀盐处理,丙二醛（MDA）含量显著下降（P<0.05）。不均匀盐处理条件下植株光合能力相对于均匀盐处理也得到显著改善,主要体现在显著升高的光合速率（Pn）、气孔导度（Gs）和蒸腾速率（Tr）;相较于均匀盐处理,在不均匀盐处理条件下50/150、0/200的荧光参数实际光化学效率（ΦPSⅡ）、最大光化学效率（Fv/Fm）和电子传递效率（ETR）分别提高了5.64%和19.00%、9.25%和18.89%、1.93%和6.89%,其中0/200处理的ΦPSⅡ和Fv/Fm与100/100处理的差异达到显著性水平（P<0.05）。【结论】 不均匀盐处理和均匀盐处理对高粱幼苗生长均产生抑制,但在不均匀盐胁迫条件下,由于低盐或无盐一侧根系补偿性增长,整个根系形态得到改善,叶片抗氧化酶活性、渗透调节能力和光合能力均有一定程度提高,因而缓解盐胁迫对高粱幼苗的危害。

Effects of Heterogeneous Salinity Across Rhizosphere on the Growth of Sorghum Seedlings

【Objective】Salt content is usually unevenly distributed in saline-alkali lands. Studies on growth and development, and the changes of physiological and biochemical indexes of sorghum seedlings under non-uniform salt stress could provide a theoretical basis for the cultivation of sorghum in saline-alkali land and the efficient exploitation and utilization of saline-alkali lands.【Method】Roots of sorghum were divided into two equal portions by a root-split method and put in uniform and non-uniform NaCl concentration solution, respectively. There were four treatments. No sodium chloride (denoted as 0/0) was the control, 0 and 200 mmol·L ^-1(denoted as 0/200), 50 mmol·L ^-1 and 150 mmol·L ^-1(denoted as 50/150) were non-uniform salinity treatments, and 100 mmol·L ^-1/100 mmol·L ^-1 (denoted as 100/100) were uniform salinity treatment. Healthy sorghum seedlings after growing for 14 days in a growth chamber were sampled for the determination of biomass, leaf area, SPAD, root morphology, osmotic regulators content, anti-oxidative enzyme activity, and photosynthetic parameters. 【Result】 Growth of sorghum both in uniform and non-uniform salt stress conditions was severely inhibited, and significant decrease of fresh weight, biomass, leaf area, root morphology, photosynthetic capacity, anti-oxidative enzyme activity and osmotic substance content accumulation was found. Dry weight per plant was increased by 21.19% and 62.71%, fresh weights of seedlings was increased by 35.39% and 86.44%, and leaf area was increased by 13.22% and 88.66%, respectively under 50/150 and 0/200 compared with those under 100/100. Under 50/150 treatment, fresh and dry weights of roots in the 50 mmol·L ^-1 side were 1.90 and 2.10 times of the 150 mmol·L ^-1 side. Under 0/200 treatment, fresh and dry weights of roots in 0 mmol·L ^-1 side were increased by 3.02 and 3.75 times compared with the 200 mmol·L ^-1 side. Likewise, local root morphology was affected significantly in non-uniform salt treatment. Root length, root volume, root tip number, and root branch number of sorghum seedlings in 50 mmol·L ^-1 side or 0 mmol·L ^-1 were significantly increased compared with 150 mmol·L ^-1 (50/150) or 200 mmol·L ^-1 (0/200) salt stress side, respectively. Root length, root volume, root tip number, and root branch number of the whole root were significantly increased under 0/200 (P<0.05) compared with the 100/100 treatment. Activities of SOD, CAT, and POD in leaves were significantly higher under non-uniform salt stress (P<0.05). Contents of proline and soluble sugars were significantly increased in leaves with a dramatic reduce in MDA content (P<0.05) under the non-uniform salinity treatments. Compared with seedlings under the 100/100 condition. Photosynthesis of sorghum was significantly enhanced under 0/200 and 50/150 salt stresses, which chiefly was reflected by notably increased photosynthetic rate, stomatal conductance, transpiration rate, and decreased intercellular CO₂ concentration (P<0.05). With respect to indexes of fluorescence of photosynthesis, such as ΦPSⅡ, Fv/Fm, and ETR, their values under 50/150 and 0/200 were increased by 5.64% and 19.00%, 9.25% and 18.89%, and 1.93% and 6.89%, respectively. ΦPSⅡ and Fv/Fm under 0/200 were significantly different from those under 100/100 (P<0.05).【Conclusion】Both non-uniform and uniform salt stress treatments caused growth inhibition to sorghum seedlings. However, due to the root compensatory growth of low salt or salt-free side under the non-uniform salt stress condition, whole root morphology, leaf antioxidant enzymes activity, osmotic regulation ability, and photosynthetic capacity were improved in a certain degree. Thus, non-uniform salinity could relieve damages to sorghum seedling initiated by salt stress.