海藻肥对菜心抗旱性的影响及其机理探究

Effect and mechanism of seaweed fertilizer increasing the drought stress resistance of flowering Chinese cabbage

【目的】结合田间试验和盆栽试验,研究海藻肥对干旱胁迫条件下菜心产量和品质的影响,探讨其提高菜心抗旱性可能存在的机理,为海藻肥在叶菜上的应用提供理论支撑。【方法】1)田间试验以‘碧清菜心’为材料,于2017年分别在广州(华南主产区)和宁夏(供港澳有机蔬菜种植基地)开展,土壤水分设为正常供水(70%~75%田间土壤最大持水量)和干旱(50%~55%田间土壤最大持水量)两个水平,设置清水对照(CK)、海藻提取物(SE)、水溶化肥(NPK)、海藻肥(NPK+SE)4个处理。在菜心移栽7、14和21天时进行冲施,每次用量10 L/m2。移栽28天后收获,测定海藻肥对菜心经济产量和品质的影响。2)盆栽试验于2018年在华南农业大学遮荫网室开展,正常供水只设清水对照(CK),干旱条件下施肥处理同田间试验,施肥量改为100 mL/株。在移栽后14、21和28天时,测定菜心最大叶长、最大叶宽、株高,移栽后28天(收获时)测定叶片相对含水量,叶绿素和自由基含量,抗氧化酶活性和养分吸收量。3)利用不同孔径的醋酸纤维超滤膜将海藻提取物分为分子量>10 kDa、5~10 kDa、3~5 kDa和<3 kDa等4种海藻提取物组分,测定其体外自由基清除能力及其对菜心抗旱性的影响。【结果】1)田间试验结果表明,广州试验点正常供水条件下,与NPK处理相比,NPK+SE处理的菜心经济产量差异不显著,但干旱条件下显著增产;宁夏试验点在干旱和正常供水条件下,NPK+SE处理的菜心经济产量均显著高于NPK处理。广州试验点干旱和正常供水条件下,NPK+SE处理的各品质指标均高于NPK处理。宁夏试验点正常供水条件下,NPK+SE处理的菜心可溶性糖和可溶性蛋白含量较CK增加显著,而干旱条件下所有品质指标均显著增加。2)盆栽试验结果显示,干旱条件下,SE处理的部分菜心品质指标值高于正常供水对照。收获时与NPK处理相比,NPK+SE处理显著提高了菜心株高、最大叶长和叶宽,鲜重显著增加12.60%,菜心叶绿素含量提高了10.24%,抗氧化酶活性提高27.84%~43.40%,叶片自由基含量降低了24.88%~41.56%。此外,NPK+SE处理的菜心氮、磷和钾吸收量分别较NPK处理增加了14.48%、16.41%和35.37%。3)4个分子量不同的海藻提取物组分中,主要活性成分海藻酸、褐藻多酚、甘露醇在<3 kDa组分中的含量高于其他3个分子量组分。对超氧阴离子和羟基自由基的清除能力由大到小依次为<3 kDa、>10 kDa、5~10 kDa、3~5 kDa,以<3 kDa组分对干旱条件下菜心的促生作用最强。【结论】两个试验点的结果都表明,海藻提取物与水溶肥配合冲施可以显著提高菜心的经济产量和品质,干旱条件下的效果更显著。海藻提取物能够提高菜心的叶绿素含量、降低叶片自由基累积、增加氮磷钾的吸收,从而提高菜心抗旱性。<3 kDa海藻提取物中的活性成分含量最高,因此,分子量<3 kDa的海藻提取物的自由基清除能力最强,对菜心的抗旱性提高效果最好。

【Objectives】This study explores the effect and mechanism of seaweed fertilizer on the yield and quality of flowering Chinese cabbage under drought stress condition using a combination of field and pot experiments.The aim was to provide theoretical support for applying seaweed fertilizer in leafy vegetables.【Methods】Field experiments were conducted in Guangzhou and Ningxia in 2017,taking flowering Chinese cabbage as test materials.Under normal water and drought stress conditions(70%-75% and 50%-55% of the maximum field moisture capacity),the vegetable seedlings were subjected to treatments of seaweed extracts(SE),soluble chemical fertilizer(NPK),seaweed fertilizer(NPK+SE),and the control had no extract or fertilizer.The economic yield and quality of the vegetable were determined.Pot experiments were conducted in the greenhouse of South China Agricultural University in 2018.The fertilizer treatments were the same as those used for the field experiments under drought stress conditions and only a water control treatment under normal water condition(CK0).The leaf length,leaf width,and plant height of flowering Chinese cabbage were measured at 14 days,21 days and 28 days after transplanting.The relative water content of leaf,the chlorophyll content,malonaldehyde(MDA),proline and free radical,antioxidant enzyme activities,and nutrient uptake were measured after harvest.The same pot experiment was also conducted using seaweed extracts divided into fractions of>10 kDa,5-10 kDa,3-5 kDa and<3 kDa molecular weight by ultrafiltration membrane.【Results】In the two field experiments,NPK+SE treatment increased the yield and quality of flowering Chinese cabbage than NPK treatment,and the increment under drought stress was higher than under normal water condition.The results of pot experiments under drought stress condition showed that SE treatment did not exhibit growth and yield increase effect,compared with CK treatment.However,NPK+SE treatment significantly increased the plant height,leaf length and leaf width,compared with NPK treatment.Also,NPK+SE treatment increased chlorophyll contents in leaves by 10.24%,enhanced the antioxidant enzymes activities by 27.84%-43.40%,decreased free radical contents by 24.88%-41.56%,and improved the N,P and K uptake by 14.48%,16.41%,and 35.37%,respectively.Among the four fractions of SE,the contents of alginate acid,polyphenols,and mannitols were higher in<3 kDa fraction than those in the other fractions.The scavenging rate of superoxide anions and hydroxyl radicals of<3 kDa fraction was significantly higher than those of other fractions,and the growth-promoting effect of<3 kDa fraction was the strongest under drought stress condition.【Conclusions】Seaweed fertilizer significantly increased the yield and quality of flowering Chinese cabbage under drought stress condition,in both field and pot experiments.SE could increase the chlorophyll content,reduce the accumulation of free radicals in leaves,increase the nutrient uptake of flowering Chinese cabbage,and thus improve the drought resistance of the crop.As the main active components existing in the SE fraction of molecular weight<3 kDa,it has the most potent effect on improving the drought resistance of flowering Chinese cabbage.