PAEs胁迫对高/低累积品种水稻根系形态及根系分泌低分子有机酸的影响

Effects of PAE Stress on Root Morphology and Low Molecular Weight Organic Acid(LMWOC) in Root Exudates of Rice(Oryza sativa L.) Cultivars with Highand Low-PAE Accumulation

以前期筛选获得的邻苯二甲酸酯（PAEs）高/低累积基因型水稻（Oryza sativa L.）品种（培杂泰丰/丰优丝苗）进行水培试验,分别于分蘖期和拔节期采集样品,采用根系扫描仪分析根系形态学特性、高效液相色谱法测定根系分泌物中低分子有机酸成分,以及采用气相色谱-质谱仪（GC-MS）测定水稻根、茎、叶中PAEs质量分数。对比研究两种基因型水稻的根系形态特征和根系分泌物（低分子有机酸）的差异,初步探讨两种基因型水稻吸收累积PAEs差异原因,为保障农产品质量安全提供科学依据。结果表明,随着培养液中PAEs质量浓度增加,两种基因型水稻总根长、根表面积和根体积先增大后减小;相同PAEs质量浓度下,高累积型品种培杂泰丰根系形态指标大多高于丰优丝苗。两种水稻体内的PAEs质量分数均随污染物浓度增大而升高,高PAEs水平（80 mg·L^-1）处理是低PAEs水平（20 mg·L^-1）处理的3.8-7.3倍（邻苯二甲酸二丁酯（DBP））和2.7-20.4倍（邻苯二甲酸二（2-乙基己基）酯（DEHP））,培杂泰丰高于丰优丝苗。植物体内DBP和DEHP质量分数呈现根〉叶≥茎。分蘖期两种水稻体内DBP和DEHP质量分数高于拔节期,且与营养液中PAEs的质量浓度呈显著相关,但拔节期的相关程度减弱。拔节期两种水稻根系分泌物中低分子有机酸质量浓度随培养液中PAEs质量浓度升高呈现不同的变化规律,但二者草酸质量浓度均增加（在1.11-8.13 mg·L^-1之间）,并与根系中DBP和DEHP的质量分数呈显著正相关。说明PAEs胁迫会影响水稻根系形态和低分子有机酸分泌,进而影响水稻对PAEs的吸收累积。

Two different genotypic cultivars of rice （Oryza sativa L.） with PAE （phthalic acid esters） high-accumulation （cultivar Peizataifeng） and low-accumulation （cultivar Fengyousimiao）, were grown in hydroponic systems contaminated with PAEs （0, 20, 40, and 80 mg·L^-1）. Plant samples were collected at tillering and jointing stage, root morphological properties were analyzed by root scanner, low molecular weight organic acids in root exudates were determined by HPLC, and di（2-ethylhexyl） phthalate （DEHP） and di-n-butyl phthalate （DBP） in roots, stems, and leaves of rice were analyzed using gas chromatography coupled with mass spectrometry （GC/MS）. The responses of root morphological characteristics （including total root length, root surface area, and root volume） and low molecular weight organic acid （LMWOC） in root exudates were analyzed to investigate the variation factors of high- and low-PAE accumulation of rice cultivars. The results show that, with the increase of PAE concentrations in solution, total root length, root surface area, and root volume of two cultivars increased firstly and then decreased. In the same PAE concentration, root morphological parameters of cultivar Peizataifeng were generally higher than cultivar Fengyousimiao. Change of PAE concentrations in solution was a key factor affecting early growth differences in root morphology of the two rice cultivars. PAE concentrations in the plants of two cultivars increased with PAE concentrations in solution, and those of cultivar Peizataifeng were also higher than cultivar Fengyousimiao. The concentrations of DEHP and DBP in different tissues decrease in the order of roots〉leaves≥stems. At tillering stage, PAE concentrations in the plants of two cultivars were significantly correlated with PAE concentrations in solution, but poorly correlated at jointing stage. LMWOC concentrations in root exudates of two cultivars displayed different change trends with PAE concentrations in solution, but concentrations of oxalic acid increased （ranging from 1.11 to 8.13 mg·L^-1）. Moreover, concentrations of oxalic acid were significantly positively correlated with the concentrations of DBP and DEHP in roots. These results suggested that PAE stress had effects on root morphology and LMWOC of two rice cultivars, and then affected the uptake and accumulation of PAEs in rice plants.