控制性分根区交替滴灌对苹果幼树形态特征与根系水分传导的影响

采用固定滴灌(根区一侧固定供水)、控制性分根区交替滴灌(根区两侧交替供水)和常规滴灌(紧贴幼树基部供水)3种灌水方式和3种灌水定额(固定滴灌和交替滴灌均为10、20和30 mm,常规滴灌为20、30和40 mm),对比研究了控制性分根区交替滴灌对苹果幼树形态特征与根系水分传导的影响.结果表明： 交替滴灌的根区两侧土壤出现反复干湿交替过程,常规滴灌的根区两侧土壤含水率差异不显著.在灌水定额相同时,灌水侧的土壤含水率在3种灌水方式间差异不显著.与常规滴灌和固定滴灌相比,交替滴灌显著增加了苹果幼树的根冠比、壮苗指数和根系水分传导,在30 mm灌水定额处理下,交替滴灌的根冠比分别增加31.6%和47.1%,壮苗指数增加34.2%和53.6%,根系水分传导增加9.0%和11.0%.3种灌水方式下,根干质量和叶面积均与根系水分传导呈显著线性正相关.控制性分根区交替滴灌增强了苹果幼树根系水分传导的补偿效应,促进了根系对水分的吸收利用,有利于干物质向各个器官均衡分配,显著提高了根冠比和壮苗指数.     

不同滴灌方式和NaCl处理对苹果幼树生长和水分传导的影响

为了探讨不同滴灌方式和土壤盐分对苹果(Malus pumila)幼树生长和水分传导(简称水分传导K)的影响。采用3种滴灌方式(交替滴灌(ADI, 根区两侧交替灌水)、固定滴灌(FDI, 根区固定一侧灌水)和常规滴灌(CDI, 根区两侧均灌水))和4个NaCl浓度梯度(0 (CK)、0.2% (S₁)、0.3% (S₂)、0.4% (S₃))。结果表明: 滴灌方式和NaCl浓度对苹果幼树生长和水分传导有显著影响。在相同的滴灌处理下, 随着NaCl浓度的增大, 苹果幼树的干物质、叶面积和净生长量及水分传导均显著地下降。根系水分传导(K_r)与总根干重间, 冠层水分传导(K_sh)与冠层干重间均呈显著的线性相关关系。在相同的NaCl处理下, 与CDI处理相比, ADI处理节水达50%, 平均根系干重、冠层干重、总干重、叶面积、净生长量和K_r仅分别下降了8.7%、19.24%、13.47%、11.87%、32.96%和10.72%; 这说明ADI处理对果树的生长和K_r具有明显的促进作用。在高盐分S₂和S₃处理下, ADI处理的叶水分传导(K_l+p)分别降低了33.56%和44.26%, 但ADI处理的K_r反而高出了CDI达1.13%和10.91%, 说明ADI处理增强了苹果幼树根源水力信号的传输效率和调控苹果幼树体内水分平衡的能力及抗盐分胁迫能力。ADI处理的生长状况和K_r均高于FDI。采用ADI处理进行灌溉不仅提高了节水调控能力, 而且也增强了抗盐分胁迫能力。     

根区不同灌溉方式对苹果幼苗水流阻力的影响

研究了滴灌条件下根区不同灌溉方式（交替滴灌ADI、固定滴灌FDI和常规滴灌CDI）和灌水量对苹果幼苗及各组成部分水流阻力、气孔导度和叶面积的影响.结果表明：根区灌溉方式和灌水量对苹果幼苗水流阻力（R）的影响显著; 在相同的根区灌溉方式下,苹果幼苗根系阻力（R_r）随着灌水量的减少而增大,冠层阻力（R_s）随着灌水量的减少而减小.在相同灌水量下,与常规滴灌相比,交替滴灌和固定滴灌均提高了苹果幼苗叶片和叶柄阻力（R_l+p）,降低了幼苗全株阻力（R_t）、R_r、R_s以及侧枝和主杆阻力（R_lb+mr）.在20 mm和30 mm灌水定额下,交替滴灌的R_l+p分别比常规滴灌高1.06%和0.63%.在平均节水达33%的前提下,交替滴灌和固定滴灌的平均R_l+p分别比常规滴灌高19.65%和24.34%,但交替滴灌和固定滴灌的平均R_lb+mr分别降低了4.83%和14.97%.交替滴灌和固定滴灌等局部根区不同灌溉方式通过有效减小苹果气孔导度和叶面积,提高了R_l+p,从而减少了叶片的蒸腾失水,提高了苹果幼苗的水分利用效率,通过降低R_r和R_lb+mr提高了苹果幼苗调控水分的能力和抗干旱能力.     

根系分区交替滴灌对苹果幼苗生理特性和水分利用效率的影响

以矮化红富士苹果幼苗为试验材料,采用交替滴灌(ADI)、固定滴灌(FDI)和常规滴灌(CDI)3种滴灌方式和3种灌水量对苹果幼苗的生理特性和水分利用效率进行了研究,以阐明根系分区交替灌溉下苹果幼苗生理特性和节水机理.结果表明:与CDI方式相比,当灌水定额由20 mm增大到30 mm时,ADI方式提高了苹果幼苗根干重、根系导水率、叶水势和净光合速率,降低了其蒸腾速率、棵间蒸发量和蒸散量,从而使得ADI方式下的叶片水分利用效率、总水分利用效率和灌溉水分利用效率较CDI方式大大提高;3种滴灌方式的根系导水率均存在显著的季节变化,并以8月份最大,12月份最小;与CDI方式相比, ADI和FDI方式在节水达33.3%时的平均根系导水率仅分别降低了5.81%和14.7%,但水分利用效率、灌溉水利用效率分别较CDI方式高出16.31%和14.48%、40.52%和27.65%.可见,局部根区灌溉方式能促进苹果幼苗生长和光合作用,并主要通过提高根系导水率的途径来提高水分利用效率.     

分根区干湿交替对玉米光合速率及蒸腾效率的影响

以玉米为材料研究了分根区干湿交替对叶片光合速度及蒸腾效率的影响,结果发现控制１／２根区交替供水和固定１／２根区供水在减少用水量的同时,叶片蒸腾速度明显下降,而光合速度不明显,蒸腾效率提高;控制１／２根区交替供水比固定１／２根区供水在光合维持高水平稳定时所要求的土壤含水量低,其蒸腾效率较高。干湿交替能够增加根冠比、根干重和根九。证明控制性分根交灌溉可提高玉米腾效率达到节水的目的。     

根区湿润方式对玉米根系生长发育的影响

将厚塑料紧密地固定在盆栽试验用桶壁和底的中央,玉米种子播种于厚塑料布的正上方,在均匀灌水、固定部分根区灌水和根系分区交替灌水3种方式下,分期测定两个1／2根区根系的长度、面积、干重以及单位面积的平均根长和比根长,研究不同根区根系的生长发育特征。结果表明,处理40d时,与其他根区相比,固定灌水非灌水区的比根长和单位面积平均根长明显增大,说明土壤水分减少使根系直径变小。根面积、长度以及干重的增长速率均表现为,处理0～5d内,与均匀灌水及其非灌水区相比,两种局部灌水的灌水区均显著增大;处理10～15d内,交替灌水的灌水区较其他根区明显增大,固定灌水的灌水区与均匀灌水相近。固定灌水时,灌水区根系的面积、长度、干重及其增长速率较之非灌水区显著增大;交替灌水时,两个根区的增长速率呈交替变化,其绝对数值随时间延长趋于相同。表明交替灌水不仅可刺激供水区根系的补偿生长,而且对恢复供水区也有补偿效应,并能够促使不同根区的根系均衡发展。     

灌水量对小桐子形态特征和水分利用的影响

小桐子是能源作物中最具发展潜力的原料树种,而土壤水分是影响小桐子苗木质量和水分利用效率的关键.设置4个灌水处理(W1:472.49 mm;W2:228.79 mm;W3:154.18 mm和W4:106.93 mm),研究灌水量对小桐子幼树生长、形态特征和水分利用的影响.结果表明:与W1相比,W2、W3和W4处理小桐子叶面积和基茎截面面积显著降低,胡伯尔值显著增加,提高了根系向叶片传输水分的效率,提高小桐子抗旱能力;W2处理根系和冠层干物质量显著降低,粗高比增加,但壮苗指数变化不显著,而W3和W4处理壮苗指数显著降低.表明灌水量228.79~472.49 mm有利于小桐子壮苗指数的提高.与W1相比,W3处理节约灌水量达67.4%,总干物质量和蒸散量分别显著降低17.4%和68.6%,因此,小桐子灌溉水利用效率和总水分利用效率显著增加153.2%和163.2%.本试验条件下,有利于小桐子水分利用效率提高的最佳灌水量为154.18 mm.     

不同膜下滴灌方式对设施黄瓜生理特性及水分利用效率的影响

为了探明黄瓜膜下分根交替滴灌的节水效果,为设施黄瓜节水灌溉提供理论依据和技术参数,以‘津优3号’黄瓜为试材,采用随机区组设计,以土壤田间持水量的65%为灌水下限,田间持水量的90%为灌水上限,研究了分根交替滴灌(APDI)、固定1/2根区滴灌(FPDI)和传统滴灌(CDI)3种灌溉模式对黄瓜生长、生理特性、产量与品质及水分利用效率的影响,结果表明:(1)随灌溉处理时间的延长,3种灌溉模式的单株叶面积和株高的差异越来越显著,而茎粗和叶片数差异不显著;(2)与传统滴灌相比,分根交替滴灌模式下黄瓜叶片净光合速率略有下降而蒸腾速率显著降低,水分利用效率显著提高;(3)分根交替滴灌处理下黄瓜可溶性蛋白、可溶性糖含量与传统滴灌相比差异不显著,Vc含量却显著增加;(4)分根交替滴灌模式下黄瓜产量比传统滴灌下降1.5%,而灌水量减少17%,水分利用效率提高18.6%,节水效果显著。综上所述,分根交替滴灌可以在保证设施黄瓜产量没有显著下降的前提下,改善品质和显著提高水分利用效率,可作为设施节水提质增效的一种灌溉模式,推广应用前景广阔。     

不同灌溉方式对玉米根毛生长发育的影响

在盆栽条件下,采用分根装置,在光学显微镜和电子显微镜下对均匀灌水、固定部分根区灌水和根系分区交替灌水3种方式下各1/2根区的根毛发育状况进行观察并采样照相,研究不同根区根毛的生长发育特征.结果表明：处理40 d时,固定部分根区灌水条件下,非灌水区的根毛有明显退化脱落现象,退化区所占比例为20.96%,明显大于其他根区;灌水区的根系发黄,有腐烂斑,且根分枝有退化现象,根毛密集区的密集程度不如非灌水区,但根毛退化区所占比例小（15.72%）,退化程度轻.均匀灌水根系的根毛发育状况与固定灌水的灌水区类似.交替灌水条件下,先灌水区和后灌水区根毛密集区的密集程度均较高,根毛退化脱落区分别占9.77%和10.38%,明显小于均匀灌水和固定灌水.说明采用交替灌水方式可促进根系根毛的生长发育,而持续湿润或干燥不利于根系根毛的生长发育.     

交替地下滴灌对春玉米产量和水分利用效率的影响

采用自动式遮雨棚水分精量控制试验研究了交替地下滴灌条件下不同灌溉定额对春玉米产量和水分利用效率的影响.结果表明:交替地下滴灌春玉米需水关键时期为拔节-抽雄期、抽雄-灌浆期,具体表现为耗水模系数与耗水强度大,且对水分敏感性高,在灌溉条件有限的情况下要优先满足春玉米这两个时期的水分需求.随着灌溉定额的增加,产量呈现增加趋势;灌溉定额小于2764.5 m³·hm^-2时产量随灌溉定额增加快速增加,大于2764.5 m³·hm^-2时产量随灌溉定额增加缓慢增加;当灌溉定额为3357.1 m³·hm^-2时产量最高,达12109.0 kg·hm^-2.与固定地下滴灌相比,在灌溉定额相同条件下,交替地下滴灌产量提高5.4%,水分利用效率提高1.4%,灌溉水利用效率提高5.6%.与固定地下滴灌相比,灌溉定额减少20%时,交替地下滴灌虽然产量下降1.8%,但水分利用效率提高11.0%,灌溉水利用效率提高22.7%.综合考虑产量、水分利用效率两个指标,确定试验区春玉米交替地下滴灌的适宜灌溉定额为1600.4～3357.1 m³·hm^-2.     

Arsenate-induced phytochelatins in white lupin: influence of phosphate status

White lupin ( Lupinus albus L.) is adapted to environments of low pH and low available phosphorus through the development of proteoid roots. The high-affinity phosphate/arsenate uptake system is much less sensitive to downregulation by phosphate in white lupin than in other plants. Arsenate is a phosphate analogue and its toxicity to plants is intimately linked to phosphate nutrition. The synthesis of phytochelatins (PCs) has been proposed as a detoxification mechanism for arsenic (As) in plants. The aim of this research was to study PC production by lupin plants in response to As, and the impact of the arsenate–phosphate interaction on PC production. PCs were the most abundant thiols in white lupin under high As exposure, reaching levels higher than in other plants tested. Together, glutathione (GSH) and PCs were able to complex the majority of As in shoots, while an additional PC-independent mechanism might function in roots. P deficiency increased As concentrations in plant tissues, causing an increase in PC accumulation and an increase in the average size of PCs. A direct relationship was observed between PC concentrations and the level of stress caused by As, i.e. the degree of growth inhibition in plants. This study suggests a key role for PCs and GSH in As detoxification by white lupin, especially in shoots. PC analysis may be useful as an early indicator of As exposure and as a tool to assess the degree of As stress of plants, even under P deficiency.     

外源二甲基砷对油菜生长及土壤中砷生物有效性的影响

通过盆栽试验研究了土壤中添加外源二甲基砷(DMA)对油菜(Brassica campestris)生长及土壤中砷生物有效性的影响.结果表明:随着外源DMA添加量的增加,油菜的出苗率和生物量均在一定程度上表现出了低浓度促进而高浓度抑制的现象.当外源DMA添加量达到90 mg·kg-1时,第2季盆栽油菜的出苗率和生物量与对照相比分别下降了9.5%和57.0%,表明DMA对油菜生长的影响具有长期性;随着外源DMA浓度的增加,土壤中有效态砷及油菜体内的砷含量均表现出增加的趋势,相关性分析表明,该三者间具有极显著相关关系;添加入土壤中的DMA主要发生去甲基化作用,产物主要为As(V)及少量的As(Ⅲ),且随着外源DMA添加量的增加,As(V)和As(Ⅲ)的浓度均表现出增加的趋势.     

Enhanced arsenic accumulation by engineered yeast cells expressing Arabidopsis thaliana phytochelatin synthase

Phytochelatins (PCs) are naturally occurring peptides with high-binding capabilities for a wide range of heavy metals including arsenic (As). PCs are enzymatically synthesized by phytochelatin synthases and contain a (gamma-Glu-Cys)(n) moiety terminated by a Gly residue that makes them relatively proteolysis resistant. In this study, PCs were introduced by expressing Arabidopsis thaliana Phytochelatin Synthase (AtPCS) in the yeast Saccharomyces cerevisiae for enhanced As accumulation and removal. PCs production in yeast resulted in six times higher As accumulation as compared to the control strain under a wide range of As concentrations. For the high-arsenic concentration, PCs production led to a substantial decrease in levels of PC precursors such as glutathione (GSH) and gamma-glutamyl cysteine (gamma-EC). The levels of As(III) accumulation were found to be similar between AtPCS-expressing wild type strain and AtPCS-expressing acr3Delta strain lacking the arsenic efflux system, suggesting that the arsenic uptake may become limiting. This is further supported by the roughly 1:3 stoichiometric ratio between arsenic and PC2 (n = 2) level (comparing with a theoretical value of 1:2), indicating an excess availability of PCs inside the cells. However, at lower As(III) concentration, PC production became limiting and an additive effect on arsenic accumulation was observed for strain lacking the efflux system. More importantly, even resting cells expressing AtPCS pre-cultured in Zn(2+) enriched media showed PCs production and two times higher arsenic removal than the control strain. These results open up the possibility of using cells expressing AtPCS as an inexpensive sorbent for the removal of toxic arsenic.     

Evidence for a role of phytochelatins in regulating arsenic accumulation in rice grain

Phytochelatins (PCs) play a crucial role in detoxifying cellular arsenic (As) through complexation of arsenite. Here, we investigated whether PCs influence As accumulation in rice grain by using six rice cultivars varying in grain As accumulation. The cultivars with low grain As had significantly higher PCs concentration in the shoots than the cultivars with high grain As, but lower glutathione concentration. Shoot PCs concentration correlated negatively with grain As accumulation. Foliar sprays with 0.5 mM l-buthionine-sulphoxime (BSO) on rice leaves at grain filling stage decreased GSH and PC accumulation in rice shoots by 40-63% and 20-55%, respectively, but did not significantly affect plant growth. Foliar sprays with BSO decreased shoot As concentration, while increased As concentrations in husk and brown rice significantly. These results suggest that PC complexation of arsenite in rice leaves reduces As translocation from leaves to grains, and implicate that manipulation of PC synthesis might mitigate As accumulation in rice grain.     

淹水条件对土壤砷形态转化的影响

通过淹水条件下的培养试验, 探讨了外源二甲基砷酸（DMA）、一甲基砷酸（MMA）、砷酸盐［As(V)］在土壤中的动态转化规律. 结果表明: 随着培养时间的推移, 加入土壤中的DMA和MMA均主要转化为As(V), 且土壤中As(V)含量均呈增加趋势, 培养到150 d时土壤中As(V)含量均显著高于1 d时的含量(P<0.01). 外源DMA通过脱甲基化作用, 在30 d内即基本转化为As(V), 且有少量的亚砷酸盐［As(Ⅲ)］生成; 而外源MMA的转化速度相对较慢, 培养60 d后才基本完成向As(V)的转化, 同时伴随少量DMA和As(Ⅲ)的生成; 在淹水条件下外源As(V)含量随培养时间的增加而逐渐降低,该过程中除有少量As(Ⅲ)生成外,其形态基本未发生改变.     

Effects of arsenate (AS5+) on growth and production of glutathione (GSH) and phytochelatins (PCS) in Chlorella vulgaris

The effect of arsenate (As5+) on growth and chlorophyll a production in Chlorella vulgaris, its removal by C. vulgaris and the role of glutathione (GSH) and phytochelatins (PCs) were investigated. C. vulgaris was tolerant to As5+ at up to 200 mg/L and was capable of consistently removing around 70% of the As5+ present in growth media over a wide range of exposure concentrations. Spectral analysis revealed that PCs and their arsenic-combined complexes were absent, indicating that the high bioaccumulation and tolerance to arsenic observed was not due to intracellular chelation. In contrast, GSH was found in all samples ranging from 0.8 mg/L in the control to 6.5 mg/L in media containing 200 mg/L As5+ suggesting that GSH plays a more prominent role in the detoxification of As5+ in C. vulgaris than PC. At concentrations below 100 mg/L cell surface binding and other mechanisms may play the primary role in As5+ detoxification, whereas above this concentration As5+ begins to accumulate inside the algal cells and activates a number of intracellular cell defense mechanisms, such as increased production of GSH. The overall findings complement field studies which suggest C. vulgaris as an increasingly promising low cost As phytoremediation method for developing countries.     

外源钙对黑藻抗镉胁迫能力的影响

以分布广泛的沉水植物——黑藻为实验材料,对比研究了Cd胁迫和施加适宜浓度的外源Ca后,黑藻体内Cd积累、矿质营养、光合色素、可溶性蛋白、渗透调节物质、抗氧化能力以及非蛋白巯基(NP-SH)和植物络合素(PCs)的变化,以探讨Ca缓解水生植物Cd毒害的生理生化机制。结果表明:(1)Cd胁迫使黑藻体内Cd含量极显著增加,并造成明显的矿质营养失衡,主要表现为显著降低了P、K、Fe、Cu、Mn的含量,而外源Ca则削弱了黑藻对Cd的蓄积,并在一定程度上减轻了Cd胁迫所造成的矿质元素失衡;(2)Cd处理使黑藻体内叶绿素含量、叶绿素a/b值和可溶性蛋白含量大幅度下降并显著降低了黑藻的总抗氧化能力(T-AOC)和小分子保护物质[谷胱甘肽(GSH)、抗坏血酸(AsA)]的含量,而外源Ca延缓了黑藻的失绿症状,促进了可溶性蛋白的合成并提高了黑藻的抗氧化能力;(3)Cd胁迫使黑藻体内脯氨酸积累显著,而外施Ca减缓了其积累;可溶性糖变化趋势与之相反;(4)Cd胁迫诱导了NP-SH和PCs在黑藻体内的大量累积,外源Ca处理后,其增加幅度减小。以上结果说明外源Ca能通过抑制Cd的吸收,促进光合色素、可溶性蛋白和可溶性糖的合成,维持高的总抗氧化能力和抗氧化物质含量以及矿质营养平衡等途径来增强黑藻对Cd胁迫的抗性。     

Active arsenic species produced by GSH-dependent reduction of dimethylarsinic acid cause micronuclei formation in peripheral reticulocytes of mice

Dimethylarsine and trivalent dimethylated arsenic, metabolites of inorganic arsenics, have received considerable attention in current research because of their biological activities. We attempted to determine the appearance of micronucleated reticulocytes (MNRETs) in mouse peripheral blood following intraperitoneal administration of dimethylarsinous iodide (DMI) and trimethylarsine (TMA), model compounds of trivalent dimethylated arsenic and dimethylarsine, respectively. A significant increase in the number of MNRETs was observed with TMA, but not with DMI. Furthermore, MNRETs only appeared with 10.6 mg/kg of dimethylarsinic acid (DMA) following its co-injection with reduced glutathione (GSH). These results suggest that micronucleus formation may need further metabolic reduction of trivalent dimethylated arsenic, i.e. the production of dimethylarsine, by an excess amount of GSH. Meanwhile, the increase in MNRETs by administration of arsenite at 7.6 mg/kg, an equivalent dose to DMA as As, was remarkably diminished by co-administration with GSH. These results indicate that GSH plays an important role in the genotoxic process of arsenics, particularly by dimethylated arsenic.     

The identification and quantification of arsenic-induced phytochelatins—comparison between plants with varying As sensitivities

The results presented in this paper provide evidence for the role of phytochelatins (PCs) in the detoxification of arsenic in six nonhyperaccumulating plant species, Agropyron repens, Glecoma hederacea, Leonurus marrubiastrum, Lolium perenne, Urtica dioica and Zea mays, in a pot experiment with high phosphate treatment. These plants differed in their arsenic sensitivities and were selected to investigate whether PCs with longer chains in roots of arsenic-tolerant species are synthesized. Raised concentrations of total PCs were measured in plant species with a range of sensitivities to arsenic at equivalent levels of arsenic exposure, determined as the inhibition of root biomass. In addition, the production of PCs as a function of accumulated arsenic was studied. Long-term PC synthesis (over a 5-week period) was positively, but non-linearly correlated with arsenic, suggesting that probably not all As is bound by PCs. Moreover, it could be shown that the synthesis of different chain lengths of PCs is associated with differences in As tolerance. In the more tolerant grasses A. repens and L. perenne it was chiefly the dithiol PC2 which was measured. In contrast, the dominant PC species in the less tolerant plants U. dioica, G. hederacea, L. marrubiastrum and Z. mays was PC3, while PC2 and PC3 were detected as well. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

The response of tomato (Lycopersicon esculentum) to different concentrations of inorganic and organic compounds of arsenic

Tomato plants were cultivated in greenhouse and water solutions of arsenite (As(III)), arsenate (As(V)), methylarsonic acid (MA) and dimethylarsinic acid (DMA) were applied individually into cultivation substrate at two As levels, 5 and 15 mg kg⁻¹ of the substrate. Comparing the availability of arsenic compounds increased in order arsenite = arsenate < MA < DMA where the arsenic contents in plants decreased during vegetation period. Within a single plant, the highest arsenic concentration was found in roots followed in decreasing order by leaves, stems, and fruits regardless of arsenic compound applied. Arsenic toxicity symptoms reflected in suppressed growth of plants and a lower number and size of fruits were most significant with DMA treatment. However, the highest accumulation of arsenic by plants growing in the soil containing DMA was caused by higher mobility of this compound in the soil due to its lower sorption affinity. Our results confirmed substantial role of transformation processes of arsenic compounds in soil in uptake and accumulation of arsenic by plants.