植物营养与肥料学报   2018, Vol. 24  Issue (4): 992-1000 
0
PDF 
复合氨基酸肥料增效剂对NaCl胁迫下小白菜种子萌发和苗期生长的影响
许猛, 袁亮, 李伟, 李燕婷 , 李娟, 赵秉强    
中国农业科学院农业资源与农业区划研究所/农业部植物营养与肥料重点实验室,北京 100081
摘要: 【目的】 作物种子萌发期和苗期是对盐胁迫最为敏感的时期,盐分过高会严重影响作物种子萌发和幼苗生长。本研究以谷氨酸尾液为主要材料开发了复合氨基酸肥料增效剂 (简称增效剂),并研究其在盐 (NaCl) 胁迫条件下对种子萌发、苗期生长和生理指标的影响,旨在为谷氨酸尾液在盐碱土地区的推广应用提供科学依据和理论指导。【方法】 以小白菜种子和幼苗为供试材料,分别进行种子萌发试验和水培试验。1) 种子萌发试验:采用标准发芽试验法,种子分别经0、0.05、0.1、0.2、0.4、0.8 g/L增效剂浸种后,分别移至含0、25、50、75 mmol/L NaCl溶液中萌发,测定发芽势、发芽率、胚根长和胚芽长。2) 苗期水培试验:选取整齐一致的幼苗,缓苗后同时加入与萌发试验浓度一致的增效剂和NaCl溶液,在盐害明显后取样测定鲜重、SPAD值、根长、株高以及叶片过氧化物歧化酶 (SOD) 活性、过氧化氢酶 (CAT) 活性、过氧化物酶 (POD) 活性、丙二醛 (MDA) 含量、超氧阴离子自由基 ( $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ ) 产生速率、脯氨酸 (Pro) 含量等盐胁迫评价指标。【结果】 在0~75 mmol/L NaCl 范围内,NaCl浓度越高对小白菜种子萌发和幼苗生长的抑制作用越强,一定浓度的增效剂可不同程度地缓解NaCl对种子萌发和幼苗的胁迫。1) 在无盐胁迫下,低浓度增效剂对种子萌发具有轻微的抑制作用,而高浓度增效剂则会显著抑制种子萌发;在同一浓度NaCl胁迫下,随增效剂浓度的增加,小白菜种子发芽势、发芽率、胚根长和胚芽长均表现出先上升后下降的变化规律,增效剂浓度为0.2 g/L时效果最佳,而在0.4 g/L和0.8 g/L时则会抑制小白菜种子萌发。2) 在无盐胁迫下,随增效剂浓度增加对小白菜生长表现出先促进后抑制的效果,以0.1 g/L用量效果最好;在同一浓度NaCl胁迫下,增效剂浓度为0.05 g/L时,提高了苗期小白菜鲜重、SPAD值,并促进了根伸长和茎伸展,同时提高叶片SOD、POD、CAT活性和Pro含量,并降低MDA含量和 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率;之后随增效剂浓度的增加小白菜幼苗鲜重、SPAD值、根长和株高均表现出持续下降的趋势,而SOD、POD、CAT活性,Pro含量表现出先持平后下降的变化规律, $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率和MDA含量则表现出先上升后平稳的趋势,增效剂浓度达到0.4 g/L和0.8 g/L时小白菜幼苗生长受到明显抑制。【结论】 在无盐胁迫条件下,低浓度 (≤ 0.2 g/L) 复合氨基酸肥料增效剂可轻微抑制小白菜种子萌发,但在25~75 mmol/L NaCl胁迫条件下,则可明显促进种子萌发、提高种子发芽质量;而在相同盐胁迫条件下,低浓度复合氨基酸肥料增效剂可明显促进小白菜幼苗生长,提高叶片抗氧化酶活性、维持渗透调节物质Pro含量、增强光合作用等,以0.05 g/L效果最佳。
关键词: 肥料增效剂     NaCl胁迫     小白菜     种子萌发     苗期生长     抗氧化酶    
Effects of a fertilizer synergist containing compound amino acids on seed germination and seedling growth of pakchoi under NaCl stress
XU Meng, YUAN Liang, LI Wei, LI Yan-ting , LI Juan, ZHAO Bing-qiang    
Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences/Key Laboratory of Plant Nutrition and Fertilizer, Ministry of Agriculture, Beijing 100081, China
Abstract: 【Objectives】 Germination and seedling stages of crops are most sensitive to salt stress by restricting seed germination and seedlings growth. In this study, a fertilizer synergist containing compound amino acids (hereinafter referred to as synergist) was produced from the waste liquids of glutamate production, and the effects of the synergist on pakchoi (Brassica chinensis L.) seed germination, seedling growth and physiological indexes of leaves under salt (NaCl) stress were investigated. The results may provide guidance for uses of glutamic acid tail liquids in saline soils. 【Methods】 A pakchoi (Brassica chinensis L.) seed germination experiment and a hydroponic experiment were conducted, respectively. The first one was for the seed germination using standard method of germination test. Seeds of pakchoi were presoaked in 0, 0.05, 0.1, 0.2, 0.4, 0.8 g/L synergist solution, respectively. The presoaked seeds were moved one by one to 0, 25, 50, 75 mmol/L NaCl solution in germination dish. The germination potential, germination percentage, length of radicle and plumule were evaluated in this experiment. The second experiment was the hydroponics experiment. After recovering the seedlings, the uniform seedlings were cultivated in nutrient solution containing the same concentration of both synergist and NaCl solution with the first experiment. When salt stress showed up, plant samples were taken, and the fresh biomass weight, SPAD value, root length, plant height, contents of SOD, POD, CAT, $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ producing rate, Pro and MDA in leaves were measured. 【Results】 Seed germination and seedling growth of pakchoi were both significantly inhibited with the increasing concentrations of NaCl. Without salt stress, lower concentrations (≤0.2 g/L) of synergist had a slight inhibitory effect on the seed germination, while 0.4 g/L and 0.8 g/L synergist concentrations significantly inhibited seed germination. Under the same NaCl concentration, increase of synergist concentrations led to early increasing but later decreasing trend in germination potential, percentage germination, length of radicle and plumule of pakchoi seeds during the incubation. Furthermore, it was found that pakchoi grew best under 0.2 g/L synergist concentration while was inhibited under 0.4 g/L and 0.8 g/L synergist concentrations. Without salt stress, increase of synergist concentrations led to increasing first and then decreasing trend in pakchoi growth, and the best concentration of synergist was 0.1 g/L while pakchoi growth was inhibited under 0.4 g/L and 0.8 g/L synergist concentrations. At different NaCl concentrations, addition of 0.05 g/L of synergist improved the fresh biomass weight and SPAD value of pakchoi seedlings, promoted root elongation and stem extension, improved SOD, POD and CAT activity and Pro content, and reduced $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ producing rate and MDA content in leaves. Further increasing concentrations of synergist to higher than 0.05 g/L led to decrease in the fresh biomass weight, SPAD value, plant height and root length of pakchoi seedling, while activity of SOD, POD, CAT and proline content in leaf maintained for some time before falling down, and $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ producing rate and MDA content showed the trend of rising for a while and then stablizined. When the synergist concentration reached 0.4 g/L and 0.8 g/L, seedling growth of pakchoi was seriously suppressed. 【Conclusions】 At 25–75 mmol/L NaCl stress, lower concentrations (≤ 0.2 g/L) of the synergist can promote seed germination of pakchoi, although it has a slight inhibitory effect on the seed germination without NaCl stress. Lower concentration of synergist can also improve antioxidant enzyme activity in leaves, maintain Pro content, enhance leaf photosynthesis, promote the seedling growth of pakchoi, and show higher resistance to salt stress (0.05 g/L synergist is optimal).
Key words: fertilizer synergist     NaCl stress     pakchoi     seed germination     seedling growth     antioxidant enzyme    

种子萌发质量和幼苗生长状况的优劣决定了作物后续发育时期的生长质量乃至产量的高低,然而作物种子萌发期和幼苗期也是抵抗外界逆境胁迫最弱的时期[14]。在盐碱土和高盐分灌溉水环境中,盐害尤其是NaCl对种子萌发和幼苗的影响非常大,并且随着NaCl浓度的升高,其对作物种子萌发和幼苗生长的抑制作用越来越强[56]。在评价作物耐盐能力和筛选耐盐品种时,种子萌发期和苗期也是必要或决定性的阶段[710]。除种植耐盐品种外,使用有效的外源物质也是减轻盐害的重要手段[1112]。氨基酸作为一类肥料增效物质,具有调节作物生长发育、提高作物产量、改善作物品质、提高肥料利用率和减少环境风险等多重增效作用[1317]。最近研究[1822]表明,氨基酸类物质作为一种植物生物刺激素还能改善植物的生理特性,显著提高植物耐盐性,缓解盐胁迫对植物生长发育的抑制程度。Ertani等[18]发现由紫花苜蓿制得的蛋白水解物能够诱导抗盐胁迫响应基因的表达,降低玉米幼苗叶片Na+含量,减轻盐胁迫对幼苗生长发育的抑制症状,从而改善玉米的生理特性,促进玉米幼苗生长。Lucini等[19]利用代谢组学技术发现,在盐胁迫下植物蛋白水解物 (商品名Trainer) 能够通过诱导植物体内多种激素的表达、改善氮代谢、提高光化学PSII系统作用、缓解膜过氧化程度和刺激细胞渗透调节物质表达等多种生理生化过程,促进生长发育,增强叶片光合作用,从而提高生菜产量、改善生菜品质,缓解盐胁迫伤害。Mostafa[20]的试验同样证明,在盐胁迫下混合氨基酸能够促进茴香生长和干物质积累,显著提高茴香品质和单果重,减轻受盐害胁迫的程度。

谷氨酸尾液含有丰富的游离氨基酸。但由于谷氨酸尾液中Na+含量较高,不同工艺、高浓度的谷氨酸尾液直接使用有时还会加重盐害[16, 23],所以利用谷氨酸尾液进行的抗盐胁迫研究较少。复合氨基酸肥料增效剂 (专利号:ZL201410026086.5) 是将谷氨酸尾液经浓缩脱盐等工艺技术制得,为谷氨酸尾液的资源化利用提供了新途径。本试验研究了在NaCl胁迫下,复合氨基酸肥料增效剂对小白菜种子萌发和幼苗生长的影响,以明确该氨基酸类物质缓解盐胁迫的性能,为其在盐碱土地区的推广应用提供科学依据。

1 材料与方法 1.1 供试材料

供试作物:不结球白菜 (Brassica chinensis L.),品名‘上海青’。

复合氨基酸肥料增效剂 (以下简称增效剂):游离氨基酸含量15.4%,以谷氨酸、甘氨酸、脯氨酸、丝氨酸、天冬氨酸为主;Na+含量1.2%。

1.2 试验设计与测定 1.2.1 萌发试验

挑选整齐饱满的小白菜种子用10% NaClO消毒15分钟后,用灭菌蒸馏水冲洗3次,吸去多余水分后分别用不同浓度复合氨基酸肥料增效剂浸种12 h。增效剂浓度分别设置为0、0.05、0.1、0.2、0.4、0.8 g/L,代码分别为Z0、Z0.05、Z0.1、Z0.2、Z0.4、Z0.8。浸种完后,再用蒸馏水冲洗3次,吸去多余水分。将浸种后的种子均匀摆入铺有2层无菌滤纸的9 cm培养皿内,分别加入5 mL含0、25、50、75 mmol/L NaCl的盐液后,置于25℃人工气候箱内培养,试验期间以称重法补充蒸馏水,每皿50粒,重复4次,对照为不含NaCl的蒸馏水。从发芽初始,每天记录种子发芽数 (以胚芽达到种子长度的一半以上或胚根达到种子长度为发芽),第2天计算发芽势;第4天结束试验并计算发芽率,测定胚根长、胚芽长。发芽势 (%) = 前2天总发芽数/供测种子总数 × 100;发芽率 (%) = 前4天总发芽数/供测种子总数 × 100。

1.2.2 苗期试验

采用穴盘育苗,待长到2叶1心时选择整齐良好的小白菜幼苗,移至含有1/2 改良Hoagland’s营养液中缓苗。两天后,同时加入NaCl和增效剂到全Hoagland’s 营养液中,调节pH到6.30,各处理营养液电导率见表1。增效剂浓度设置为0、0.05、0.1、0.2、0.4、0.8 g/L,代码分别为Z0、Z0.05、Z0.1、Z0.2、Z0.4、Z0.8;盐 (NaCl) 浓度设置为0、25、50、75 mmol/L,对照为不含NaCl的营养液。每处理重复3次,每重复培养3棵幼苗。每天更换一次营养液。培养10天后,进行指标测定。

测定根长 (最长根)、株高 (地上部全长)、鲜重 (地上部和地下部之和);最大叶片SPAD值采用日本产SPAD-502叶绿素仪测定;叶片超氧化物歧化酶 (SOD) 活性采用氮蓝四唑光化学还原法[24]测定,过氧化物酶 (POD) 活性采用愈创木酚法[24]测定,过氧化氢酶 (CAT) 活性采用紫外线吸收法[25]测定,所有酶活性单位以样品鲜重为基准;丙二醛 (MDA) 含量采用硫代巴比妥酸法[25] ,叶片超氧阴离子自由基 ( $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ ) 产生速率采用羟胺氧化法[25]测定,脯氨酸 (Pro) 含量采用磺基水杨酸法[26]测定。

表1 各处理营养液电导率 (μS/cm) Table 1 The electrical conductivity values of nutrient solution in different treatments
1.3 数据处理

试验数据用Excel 2013、DPS 9.0软件进行统计分析,采用LSD法进行差异显著性检验。

2 结果与分析 2.1 复合氨基酸肥料增效剂对NaCl胁迫下小白菜种子萌发的影响

表2可以看出,NaCl浓度越高对Z0 (蒸馏水浸种) 处理的小白菜种子发芽势和发芽率抑制作用越强。在对照条件 (0 mmol/L NaCl) 下,增效剂本身对小白菜种子发芽势和发芽率表现出了抑制作用,且增效剂浓度增加到0.4 g/L时抑制作用均达到显著水平。而在25、50、75 mmol/L NaCl盐胁迫下,小白菜种子发芽势和发芽率随增效剂浓度增加呈现先上升后下降的趋势,且均以Z0.2效果最佳。

表2 不同NaCl胁迫水平下复合氨基酸肥料增效剂对小白菜种子发芽势和发芽率的影响 Table 2 Potential and percentage of germination of pakchoi seeds under different NaCl stress and fertilizer synergist addition levels

表3可以看出,NaCl浓度越高,对Z0处理小白菜种子胚根和胚芽的抑制作用越强。增效剂本身同样具有抑制作用,其对胚根长和胚芽长的抑制分别在0.4 g/L和0.2 g/L时达到显著水平。在25、50、75 mmol/L NaCl胁迫下,小白菜种子胚根长和胚芽长均随增效剂浓度增加呈现先上升后下降的趋势,增效剂浓度达到0.1~0.2 g/L时效果最好。

表3 不同NaCl胁迫水平下复合氨基酸肥料增效剂对小白菜胚根长和胚芽长的影响 Table 3 Radical and plumular lengths of pakchoi under different NaCl stress and fertilizer synergist addition levels
2.2 复合氨基酸肥料增效剂对NaCl胁迫下小白菜生长的影响

图1可以看出,随NaCl浓度上升,Z0处理小白菜鲜重呈现直线降低的趋势。在对照条件下Z0.1处理小白菜鲜重最高,在25、50、75 mmol/L NaCl盐胁迫条件下均以Z0.05处理小白菜鲜重最高,增幅分别达34.2%、36.2%和19.3%;之后随增效剂浓度继续增加,各盐浓度条件下鲜重均持续下降,在Z0.4或Z0.8处理时达到显著水平。

图1 不同NaCl胁迫水平下复合氨基酸肥料增效剂对小白菜鲜重的影响 Fig. 1 Fresh biomass weight of pakchoi under different NaCl stress and fertilizer synergist addition levels [注(Note):柱上不同字母表示相同NaCl浓度下不同处理间差异达0.05显著水平Different letters above the bars are significantly different at 5% level among the treatments at the same NaCl concentration.]

图2可以看出,NaCl浓度越高,Z0处理叶片SPAD值越低。在对照条件下,Z0.05处理对提高叶片SPAD值效果最好,随增效剂浓度继续增加,SPAD值呈下降趋势,在0.4 g/L时差异显著。在25、50、75 mmol/L NaCl胁迫下,叶片SPAD值最高处理也是Z0.05,随增效剂浓度增加SPAD值下降更快,在0.2 g/L时均已达差异显著水平。

图2 不同NaCl胁迫水平下复合氨基酸肥料增效剂对小白菜SPAD值的影响 Fig. 2 SPAD value of pakchoi under different NaCl stress and fertilizer synergist addition levels [注(Note):柱上不同字母表示相同NaCl浓度下不同处理间差异达0.05显著水平Different letters above the bars are significantly different at 5% level among the treatments at the same NaCl concentration.]

表4可以看出,在0~75 mmol/L NaCl胁迫条件下,除Z0.05处理小白菜根长与Z0处理基本持平外,其余增效剂处理均抑制了根的伸长,而株高呈先上升后下降的趋势。在对照条件下,Z0.1处理效果最好,株高增加19.9%;在25、50 mmol/L NaCl胁迫下,均以Z0.05处理小白菜株高最高,分别增加23.1%和19.5%,之后随增效剂浓度增加株高迅速降低;在75 mmol/L NaCl浓度下,Z0.1处理效果最好,但各处理之间差异均不显著。

表4 不同NaCl胁迫水平下复合氨基酸肥料增效剂对小白菜根长和株高的影响 Table 4 Root and shoot lengths of pakchoi under different NaCl stress and fertilizer synergist addition levels
2.3 复合氨基酸肥料增效剂对NaCl胁迫下小白菜叶片抗氧化酶活性的影响

表5可以看出,NaCl浓度越高对Z0处理叶片SOD活性抑制越强烈。在对照条件下,与Z0处理相比,SOD活性差异均不显著,以Z0.8处理活性最低。在25~75 mmol/L NaCl胁迫条件下,随增效剂浓度提高小白菜SOD活性均呈现先上升后下降的规律,且均以Z0.1处理最高,而高浓度增效剂尤其是Z0.8处理会抑制SOD活性。在0~75 mmol/L NaCl范围内,各浓度增效剂均能保持或提高小白菜叶片POD活性,Z0.05处理对提高叶片POD活性效果最好。对于叶片CAT活性,在0~75 mmol/L NaCl胁迫下,同样均以Z0.05处理酶活性最高,之后随增效剂浓度提高,CAT活性均有所下降,但均高于Z0处理或与Z0处理持平。在各盐浓度条件下,Z0.05处理对于提高三种酶活性方面表现突出,Z0.8处理效果最差。

表5 不同NaCl胁迫水平和复合氨基酸肥料增效剂对小白菜叶片SOD、POD和CAT活性的影响 Table 5 SOD, POD and CAT activity of pakchoi leaves under different NaCl stress and fertilizer synergist addition levels
2.4 复合氨基酸肥料增效剂对NaCl胁迫下小白菜苗期叶片活性氧和丙二醛含量的影响

表6可以看出,NaCl浓度越高,Z0处理叶片 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率越快,表明叶片膜脂过氧化程度越高,但增效剂自身对 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率影响不大。在25~75 mmol/L NaCl浓度下,低浓度增效剂小白菜叶片 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率持平或降低,而高浓度增效剂 (0.2~0.8 g/L) 会加快小白菜叶片 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率。对于叶片MDA含量,高浓度 NaCl 或高浓度增效剂均会使其显著上升。在 25~75 mmol/L NaCl胁迫条件下,低浓度增效剂可以降低小白菜叶片 MDA 含量 Z0.05 处理含量较低,表现最为突出,而高浓度尤其是 Z0.8 处理含量最高。

表6 不同NaCl胁迫水平和复合氨基酸肥料增效剂对小白菜叶片 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} 产生速率和MDA含量的影响 Table 6 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} producing rate and MDA concentration in pakchoi leaves under different NaCl stress and fertilizer synergist addition levels
2.5 复合氨基酸肥料增效剂对NaCl胁迫下小白菜苗期叶片脯氨酸含量的影响
图3 不同NaCl胁迫水平和复合氨基酸肥料增效剂对小白菜叶片脯氨酸含量的影响 Fig. 3 Pro concentration of pakchoi leaves under different NaCl stress and fertilizer synergist addition levels [注(Note):柱上不同字母表示同一NaCl浓度下不同处理间差异达0.05显著水平Different letters above the bars are significantly different at 5% level among the treatments at the same NaCl concentration.]

图3可以看出,随NaCl浓度的上升,叶片Pro含量呈现先上升后下降的趋势。增效剂本身能够促进Pro积累,增幅达31.4%~66.0%。在25、50 mmol/L NaCl胁迫下,Z0.05和Z0.1处理能够保持叶片Pro含量,之后随增效剂浓度继续增加会使Pro浓度显著下降。在75 mmol/L NaCl胁迫下Pro含量变化不一。

3 讨论 3.1 复合氨基酸肥料增效剂对NaCl胁迫下小白菜种子萌发的影响

在无NaCl胁迫条件下,低浓度 (≤ 0.2 g/L) 增效剂会轻微抑制种子萌发,浓度超过0.2 g/L会明显抑制种子萌发 (表2表3)。这是由于增效剂含有一定量的盐分 (表1),用量过高也会导致盐害,其电导率比25 mmol/L NaCl的低,而抑制种子萌发的作用更强烈,可能是过高浓度的氨基酸对种子萌发起了抑制作用。李友勇等研究表明,多种外源氨基酸在高浓度下均会强烈抑制多种作物种子萌发[27, 28]

在无NaCl胁迫条件下,增效剂虽然对小白菜种子萌发无促进作用,但在盐胁迫条件下,适宜浓度 (≤ 0.2 g/L) 的增效剂却促进了种子发芽,提高了发芽质量 (表2表3),这与沙汉景[29]在水稻种子上的研究一致。其原因很可能是在盐胁迫条件下,NaCl对种子造成的渗透胁迫和离子毒害导致蛋白酶等代谢不正常,而适宜外源氨基酸在浸种过程中随种子吸水作用进入种子内部,不仅可以提高种子蛋白酶、淀粉酶的活性,还可以降低细胞内的渗透势,缓解渗透胁迫,从而维持正常萌发过程[30, 31]。此外,种子萌发时的代谢强度与细胞质膜的完整性密切相关,氨基酸在提高种子抗氧化酶活性和缓解盐胁迫下活性氧积累对细胞质膜的伤害方面发挥了作用[32, 33]。很多研究表明[29, 3335],在盐胁迫下外源氨基酸浸种提高了种子萌发质量,萌发的种子继续培养到苗期乃至整个生育期依然会表现出良好的抗逆境胁迫能力,其原因是在有效外源物质中浸种“激活”了耐盐能力,使作物提前适应了逆境胁迫环境[711]

3.2 复合氨基酸肥料增效剂对NaCl胁迫下小白菜幼苗生长的影响

无盐胁迫条件下,增效剂对小白菜幼苗生长的影响存在浓度效应:高浓度 (≥ 0.4 g/L) 抑制幼苗生长,而低浓度 (0.1 g/L) 则能够促进幼苗生长 (图1)。研究表明,多种外源氨基酸除能够被作物直接吸收提供有机碳、氮营养外,还能够刺激作物生长、调控体内代谢,从而促进植株生长发育,但浓度高则会抑制作物生长[3639]

叶是光合作用的主要器官,高浓度NaCl会严重破坏植物叶片的结构和功能,使得叶绿素含量下降,减弱叶片的光合作用[11, 4041]。植物叶首先受到伤害的是细胞膜,盐胁迫下叶片 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率加快,MDA含量升高。 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 等活性氧积累会诱发膜脂过氧化使细胞表现出脱脂化现象,MDA是细胞脂质过氧化的最终产物,两者含量升高均表明细胞膜受损,导致离子外渗[11, 40];MDA还会引起生物大分子如蛋白质、核酸等的交联聚合,引起代谢紊乱[41]。盐胁迫产生的离子毒害作用还会对叶片光系统II反应中心造成损伤,破坏叶绿体结构,引起叶绿素降解,使光合电子传递和PSII的光合作用活力被抑制,从而减弱光合作用,使得物质和能量积累不足,抑制植株生长[11, 41]

在盐胁迫下,适宜浓度增效剂能够提高叶片叶绿素含量,增强幼苗光合作用,促进茎伸展和根伸长,增加幼苗鲜重,促进小白菜正常生长发育。研究表明[3335, 4244],在NaCl胁迫下,外源氨基酸可以通过抗氧化酶系统和渗透调节途径提高植物体耐盐能力,促进植物生长。SOD、POD和CAT是植物体内抗氧化酶系统的主要成员,能够清除植物体内的活性氧[1112];植物体内的脯氨酸可以保持细胞原生质与外界环境渗透平衡,是植物盐胁迫下积累的最重要的渗透调节物质之一,脯氨酸还能够作为逆境胁迫信号物质,诱导抗盐基因的表达,稳定和保护细胞膜结构,参与氮代谢和自由基的清除[1112, 19]。本试验中,0.05 g/L增效剂能够提高小白菜叶片SOD、POD和CAT活性,降低叶片MDA含量和 $\rm{O}_{\small 2}^{\overline {\,\cdot\,}} $ 产生速率,并维持脯氨酸含量,提高小白菜幼苗耐盐能力,从而减轻NaCl对小白菜的伤害程度,维持正常光合作用,说明增效剂可以通过提高抗氧化酶活性和维持渗透调节物质含量提高小白菜幼苗的抗盐能力。

4 结论

1) 无盐胁迫条件下,低浓度 (≤ 0.2 g/L) 复合氨基酸肥料增效剂轻微抑制种子萌发,高浓度增效剂 (0.4 g/L、0.8 g/L) 显著抑制种子萌发。在盐 (NaCl 25、50、75 mmol/L ) 胁迫条件下,低浓度 (≤ 0.2 g/L) 复合氨基酸肥料增效剂可明显缓解盐胁迫对种子萌发的抑制作用。

2) 无盐胁迫条件下,适宜浓度复合氨基酸肥料增效剂可促进小白菜幼苗生长,浓度以0.1 g/L最佳,之后随增效剂浓度的增加抑制生长作用增强。在盐 (NaCl25、50、75 mmol/L) 胁迫条件下,低浓度复合氨基酸肥料增效剂可通过提高小白菜幼苗叶片抗氧化酶活性和维持渗透调节物质脯氨酸含量,缓解盐对幼苗生长的胁迫,但随增效剂浓度增加抑制生长作用加强,最适使用浓度为 0.05 g/L。

参考文献
[1] Bennett M A, Fritz V A, Callan N W. Impact of seed treatments on crop stand establishment[J]. Horttechnology, 1992, 2(3): 345–349.
[2] Finch-Savage W E, Basra A S. Influence of seed quality on crop establishment, growth, and yield [A]. Basra A S. Seed quality: basic mechanism and agricultural implications[M]. New York: Food Products Press, 1994. 363–385.
[3] Rehman H U, Nawaz Q, Basra S M, et al. Seed priming influence on early crop growth, phonological development and yield performance of linola (Linum usitatissimum L.) [J]. Journal of Integrative Agriculture, 2014, 13(5): 990–996. DOI:10.1016/S2095-3119(13)60521-3
[4] 薛宇婷. 芦苇不同生长阶段的耐盐特性研究[D]. 南京: 南京林业大学硕士学位论文, 2015.
Xue Y T. Study on characteristic of salt-tolerance at different growth stages of phragmintes australis [D]. Nanjing: MS Thesis of Nanjing Forestry University, 2015.
[5] 石玉龙, 徐隆华, 窦声云, 等. NaCl和Na2CO3胁迫对同德老芒麦种子萌发及幼苗生长的影响 [J]. 草地学报, 2017, 25(3): 662–665.
Shi Y L, Xu L H, Dou S Y, et al. Effects of NaCl and Na2CO3 stress on seed germination and seedling growth of Elymus Sibiricus ‘Tong de’ [J]. Acta Agrestia Sinica, 2017, 25(3): 662–665. DOI:10.11733/j.issn.1007-0435.2017.03.031
[6] 鲁艳, 雷加强, 曾凡江, 等. NaCl胁迫对大果白刺幼苗生长和抗逆生理特性的影响[J]. 应用生态学报, 2014, 25(3): 711–717.
Lu Y, Lei J Q, Zeng F J, et al. Effects of salt stress on Nitraria roborowskii growth and physiological characteristics of stress resistance [J]. Chinese Journal of Applied Ecology, 2014, 25(3): 711–717.
[7] 张智猛, 慈敦伟, 丁红, 等. 花生品种耐盐性指标筛选与综合评价[J]. 应用生态学报, 2013, 24(12): 3487–3494.
Zhang Z M, Ci D W, Ding H, et al. Indices selection and comprehensive evaluation of salinity tolerance for peanut varieties[J]. Chinese Journal of Applied Ecology, 2013, 24(12): 3487–3494.
[8] 籍贵苏, 杜瑞恒, 刘国庆, 等. 高粱耐盐性评价方法研究及耐盐碱资源的筛选[J]. 植物遗传资源学报, 2013, 14(1): 25–30.
Ji G S, Du R H, Liu G Q, et al. Methodology and screen of saline-alkaline tolerance in sorghum accessions[J]. Journal of Plant Genetic Resources, 2013, 14(1): 25–30.
[9] 方先文, 汤陵华, 王艳平. 耐盐水稻种质资源的筛选[J]. 植物遗传资源学报, 2004, (3): 295–298.
Fang X W, Tang L H, Wang Y P. Selection on rice germplasm tolerant to salt stress[J]. Journal of Plant Genetic Resources, 2004, (3): 295–298.
[10] 田小霞, 毛培春, 孟林, 等. 无芒雀麦苗期耐盐指标筛选及耐盐性综合评价[J]. 干旱区资源与环境, 2017, 31(10): 156–161.
Tian X X, Mao P C, Meng L, et al. Determination of indicators for salt-tolerant evaluation and comprehensive evaluation of salt-tolerant at the seedlings of Bromus inermis [J]. Journal of Arid Land Resources and Environment, 2017, 31(10): 156–161.
[11] 王佺珍, 刘倩, 高娅妮, 等. 植物对盐碱胁迫的响应机制研究进展[J]. 生态学报, 2017, 37(16): 5565–5577.
Wang Q Z, Liu Q, Gao Y N, et al. Review on the mechanisms of the response to salinity-alkalinity stress in plants[J]. Acta Ecologica Sinica, 2017, 37(16): 5565–5577.
[12] Bernstein L. Effects of salinity and sodicity on plant growth[J]. Annual Review of Phytopathology, 1975, 13(1): 295–312. DOI:10.1146/annurev.py.13.090175.001455
[13] 李志坚, 林治安, 赵秉强, 等. 增值磷肥对潮土无机磷形态及其变化的影响[J]. 植物营养与肥料学报, 2013, 19(6): 1329–1336.
Li Z J, Lin Z A, Zhao B Q, et al. Effects of value-added phosphate fertilizers on yield and phosphorus utilization of winter wheat[J]. Journal of Plant Nutrition and Fertilizer, 2013, 19(6): 1329–1336. DOI:10.11674/zwyf.2013.0606
[14] 袁亮, 赵秉强, 林治安, 等. 增值尿素对小麦产量、氮肥利用率及肥料氮在土壤剖面中分布的影响[J]. 植物营养与肥料学报, 2014, 20(3): 620–628.
Yuan L, Zhao B Q, Lin Z A, et al. Effects of value-added urea on wheat yield and N use efficiency and the distribution of residual N in soil profiles[J]. Journal of Plant Nutrition and Fertilizer, 2014, 20(3): 620–628. DOI:10.11674/zwyf.2014.0313
[15] 赵秉强. 传统化肥增效改性提升产品性能与功能[J]. 植物营养与肥料学报, 2016, 22(1): 1–7.
Zhao B Q. Modification of conventional fertilizers for enhanced property and function[J]. Journal of Plant Nutrition and Fertilizer, 2016, 22(1): 1–7. DOI:10.11674/zwyf.14470
[16] 陈清, 陈宏坤. 水溶性肥料生产与施用[M]. 北京: 中国农业出版社, 2015. 56–61.
Chen Q, Chen H K. Water soluble fertilizer production and application [M]. Beijing: China Agricultural Press, 2015. 56–61.
[17] 袁伟, 董元华, 王辉. 植物氨基酸多元素肥料生物效应的研究进展[J]. 土壤, 2009, 41(1): 16–20.
Yuan W, Dong Y H, Wang H. Biological effect of plant amino acids trace-element fertilizers[J]. Soils, 2009, 41(1): 16–20.
[18] Ertani A, Schiavon M, Muscolo A, et al. Alfalfa plant-derived biostimulant stimulate short-term growth of salt stressed Zea mays L. plants [J]. Plant & Soil, 2013, 364(1-2): 145–158.
[19] Lucini L, Rouphael Y, Cardarelli M, et al. The effect of a plant-derived biostimulant on metabolic profiling and crop performance of lettuce grown under saline conditions[J]. Scientia Horticulturae, 2015, 182: 124–133. DOI:10.1016/j.scienta.2014.11.022
[20] Mostafa G G. Improving the growth of fennel plant grown under salinity stress using some biostimulants[J]. American Journal of Plant Physiology, 1973, 10(2): 77–83.
[21] Calvo P, Nelson L, Kloepper J W. Agricultural uses of plant biostimulants[J]. Plant & Soil, 2014, 383(1-2): 3–41.
[22] Colla G, Nardi S, Cardarelli M, et al. Protein hydrolysates as biostimulants in horticulture[J]. Scientia Horticulturae, 2015, 196: 28–38. DOI:10.1016/j.scienta.2015.08.037
[23] 刘睿, 周启星 , 张兰英, 等. 不同工艺阶段味精废水对作物种子发芽和根伸长的毒性效应[J]. 应用生态学报, 2006, 17(7): 1286–1290.
Liu R, Zhou Q X, Zhang L Y, et al. Toxic effects of monosodium glutamate waste water on crop seed germination and root elongation[J]. Chinese Journal of Applied Ecology, 2006, 17(7): 1286–1290.
[24] 李合生, 孙群, 赵世杰, 等. 植物生理生化实验原理和技术[M]. 北京: 高等教育出版社, 2000.
Li H S, Sun Q, Zhao S J, et al. The experiment principle and technique on plant physiology and biochemistry [M]. Beijing: Higher Education Press, 2000.
[25] 刘萍, 李明军. 植物生理学实验指导[M]. 北京: 科学出版社, 2007.
Liu P, Li M J. Plant physiology experiment guide [M]. Beijing: Science Press, 2007.
[26] 赵世杰, 史国安, 董新纯. 植物生理学实验指导[M]. 北京: 中国农业科学技术出版社, 2002.
Zhao S J, Shi G A, Dong X C. Plant physiology experiment guide [M]. Beijing: China Agricultural Science and Technology Press, 2002.
[27] 李友勇, 刘金枝, 陈利. 离体小麦胚胎对10种必需氨基酸的生长反应[J]. 生物技术, 2004, (5): 84–85.
Li Y Y, Liu J Z, Chen L. Growth reaction of wheat embryo in vitro to 10 kinds of essential amino acids[J]. Biotechnology, 2004, (5): 84–85.
[28] 杨靖, 孙海燕, 李友勇. 11种非必需氨基酸对离体植物生长的胁迫作用[J]. 生物技术, 2008, (4): 72–74.
Yang J, Sun H Y, Li Y Y. Stress on the growth of plants in vitro of non-essential amino acids[J]. Biotechnology, 2008, (4): 72–74.
[29] 沙汉景. 外源脯氨酸对盐胁迫下水稻耐盐性的影响[D]. 哈尔滨: 东北农业大学硕士学位论文, 2013.
Sha H J. Effect of exogenous proline on the salt-tolerance of rice (Oryza sativa L.) [D]. Harbin: MS Thesis of Northeast Agricultural University, 2013.
[30] 安华燕. 有机碳营养浸种剂的研究[D]. 合肥: 合肥工业大学硕士学位论文, 2016.
An H Y. The research of the C2-C4 organic acids and alcohols for seed priming [D]. Hefei: MS Thesis of Hefei University of Technology, 2016.
[31] Müntz K, Belozersky M A, Dunaevsky Y E, et al. Stored proteinases and the initiation of storage protein mobilization in seeds during germination and seedling growth[J]. Journal of Experimental Botany, 2001, 52(362): 1741. DOI:10.1093/jexbot/52.362.1741
[32] 檀龙颜. 油菜(Brassica napus)种子萌发响应NaCl胁迫的生理学与蛋白质组学研究[D]. 哈尔滨: 东北林业大学博士学位论文, 2014.
Tan L Y. Physiological and quantitative proteomics analysis of Brassica napus seed germination in response to NaCl [D]. Harbin: PhD Dissertation of Northeast Forestry University, 2014.
[33] 赵艳艳, 胡晓辉, 邹志荣, 等. 不同浓度5-氨基乙酰丙酸(ALA)浸种对NaCl胁迫下番茄种子发芽率及芽苗生长的影响[J]. 生态学报, 2013, 33(1): 62–70.
Zhao Y Y, Hu X H, Zou Z R, et al. Effects of seed soaking with different concentrations of 5-aminolevulinic acid on the germination of tomato (Solanum lycopersicum) seeds under NaCl stress [J]. Acta Ecologica Sinica, 2013, 33(1): 62–70.
[34] Wang X D, Guo S J, Li M F, et al. Effects of gamma-aminobutyric acid on salt tolerance of wheat[J]. Journal of Southern Agriculture, 2017, 48(10): 1761–1768.
[35] 卢元芳. 脯氨酸浸种对NaCl胁迫下玉米种子萌发和幼苗生长的效应[J]. 华南农业大学学报, 2001, (4): 62–65.
Lu Y F. Effect of seed soaked with proline on seed germination and seedling growing of corn under NaCl stress[J]. Journal of South China Agricultural University, 2001, (4): 62–65. DOI:10.7671/j.issn.1001-411X.2001.04.018
[36] 曹小闯, 吴良欢, 马庆旭, 等. 高等植物对氨基酸态氮的吸收与利用研究进展[J]. 应用生态学报, 2015, 26(3): 919–929.
Cao X C, Wu L H, Ma Q X, et al. Advances in studies of absorption and utilization of amino acids by plants: A review[J]. Chinese Journal of Applied Ecology, 2015, 26(3): 919–929.
[37] 廖宗文, 毛小云, 刘可星. 有机碳肥对养分平衡的作用初探——试析植物营养中的碳短板[J]. 土壤学报, 2014, 51(3): 656–659.
Liao Z W, Mao X Y, Liu K X. Effect of organic carbon fertilizer on nutrient balance-analysis of carbon, a short board, in plant nutrition[J]. Acta Pedologica Sinica, 2014, 51(3): 656–659.
[38] 苑婧娴. 氨基酸对小麦幼苗生长及生理特性的影响[D]. 南京: 南京农业大学硕士学位论文, 2013.
Yuan J X. Effects of amino acid on growth and physiological trait in wheat seedling [D]. Nanjing: MS Thesis of Nanjing Agricultural University, 2013.
[39] 徐菲. 16种氨基酸对水稻苗期生长的影响[D]. 广州: 华南农业大学硕士学位论文, 2008.
Xu Fei. Effects of 16 kinds of amino acids on rice germination and growth [D]. Guangzhou: South China Agricultural University, 2008.
[40] 曹齐卫, 李利斌, 孔素萍, 等. 不同黄瓜品种幼苗对等渗Mg(NO3)2和 NaCl 胁迫的生理响应 [J]. 应用生态学报, 2015, 26(4): 1171–1178.
Cao Q W, Li L B, Kong S P, et al. Physiological responses of different cucumber cultivars seedlings to iso-osmotic Mg(NO3)2 and NaCl stress [J]. Chinese Journal of Applied Ecology, 2015, 26(4): 1171–1178.
[41] 刘卫国, 丁俊祥, 邹杰, 等. NaCl对齿肋赤藓叶肉细胞超微结构的影响[J]. 生态学报, 2016, 36(12): 3556–3563.
Liu W G, Ding J X, Zou J, et al. Ultra structural responses of Syntrichia caninervis to a gradient of NaCl stress [J]. Acta Ecologica Sinica, 2016, 36(12): 3556–3563.
[42] 杜娟, 孙艳香. 氨基酸对盐胁迫下棉花幼苗生长及丙二醛和过氧化酶的影响[J]. 种子, 2015, 34(02): 8–12.
Du J, Sun Y X. Effects of amino acids on seedling growth, MDA and MPO of cotton under salt stress[J]. Seed, 2015, 34(02): 8–12.
[43] 赵宏伟, 胡文成, 沙汉景, 等. 脯氨酸和 γ-氨基丁酸复配对盐胁迫下水稻抗氧化系统的调控效应[J]. 东北农业大学学报, 2017, 10(20): 1–11.
Zhao H W, Hu W C, Sha H J, et al. Regulatory effects of combined application of proline and GABA on antioxidant system of rice under salt stress[J]. Journal of Northeast Agricultural University, 2017, 10(20): 1–11.
[44] 颜志明, 冯英娜, 韩艳丽, 等. 外源脯氨酸对盐胁迫下甜瓜脯氨酸代谢的影响[J]. 西北植物学报, 2015, 35(10): 2035–2041.
Yan Z M, Feng Y N, Han Y L, et al. Effects of proline on metabolism of Cucumis melo under salt stress [J]. Acta Botanica Boreali-Occidentalia Sinica, 2015, 35(10): 2035–2041. DOI:10.7606/j.issn.1000-4025.2015.10.2035