Lipid concentration and composition in xylem sap of woody angiosperms from a tropical savanna and a seasonal rainforest

Lipids may play an important role in preventing gas embolisms by coating nanobubbles in xylem sap.Few studies on xylem sap lipids have been reported for temperate plants,and it remain unclear whether sap lipids have adaptational significance in tropical plants.In this study,we quantify the lipid composition of xylem sap for angiosperm species from a tropical savanna(seven species)and a seasonal rainforest(five species)using mass spectrometry.We found that all twelve species studied contained lipids in their xylem sap,including galactolipids,phospholipids and triacylglycerol,with a total lipid concentration ranging from 0.09 to 0.26 nmol/L.There was no difference in lipid concentration or composition between plants from the two sites,and the lipid concentration was negatively related to species’open vessel volume.Furthermore,savanna species showed little variation in lipid composition between the dry and the rainy season.These results support the hypothesis that xylem sap lipids are derived from the cytoplasm of individual conduit cells,remain trapped inside individual conduits,and undergo few changes in composition over consecutive seasons.A xylem sap lipidomic data set,which includes 12 tropical tree species from this study and 11 temperate tree species from literature,revealed no phylogenetic signals in lipid composition for these species.This study fills a knowledge gap in the lipid content of xylem sap in tropical trees and provides additional support for their common distribution in xylem sap of woody angiosperms.It appears that xylem sap lipids have no adaptive significance.

Drought-Induced Changes in Xylem Sap pH, ABA and Stomatal Conductance

Upstream signals potentially regulating evaporation and stomatal conductance wereinvestigated using 6-8-leaf-old maize (Zea may L.) seedlings which were grown in agreenhouse. Pressure chamber was used to measure leaf water potential and to collectxylem sap. The pH of xylem sap in stems was higher than that in root, and the abscisicacid (ABA) concentration in stems was the highest in well-watered seedlings. The ABAconcentration and pH of xylem sap in roots, stems and leaves increased, and the ABAconcentration in leaves reached the maximum during drought stress. The treatment ofroots with exogenous ABA solution (100molL-1) increased xylem sap ABA concentration inall organs measured, and induced stomatal closure, but did not change ABA distributionamong organs of maize seedlings. The combined effects of external pH buffer on pH, ABAof xylem sap and stomatal behavior indicated that pH, as a root-source signal to leavesunder drought stress, regulated stomatal closure through accumulating ABA in leaves orguard cells.

Nitrogen Under-and Over-supply Induces Distinct Protein Responses in Maize Xylem Sap

Xylem sap primarily transports water and mineral nutrients such as nitrogen （N） from roots to shoots in vascular plants. However, it remains largely unknown how nitrogenous compounds, especially proteins in xylem sap, respond to N under- or over-supply. We found that reducing N supply increased amino-N percentage of total N in maize （Zea mays L.） xylem sap. Proteomic analysis showed that 23 proteins in the xylem sap of maize plants, including 12 newly identified ones, differentially accumulated in response to various N supplies. Fifteen of these 23 proteins were primarily involved in general abiotic or biotic stress responses, whereas the other five proteins appeared to respond largely to N under- or over-supply, suggesting distinct protein responses in maize xylem upon N under- and over-supply. Furthermore, one putative xylanase inhibitor and two putative O-glycosyl hydrolases had preferential gene expression in shoots.

Responses of woody plant root and xylem sap ATP to soil drying

The ATP in roots and xylem sap of two woody plant species, Platycladus orientalis and Acacia auriculiformis, subjected to rapid and slow soil drying has been determined employing firefly luciferase ATP assay method (sensitivity is at 10-12 mol ATP L-1). The ATP levels in the two species were 1.6 nmol. gDW-1 and 0.6 nmol. gDW-1 in roots, and 5.6 μmol·m-3 and 8 μmol ·m-3 in xylem sap, respectively. When plants of P. orientalis and A. auriculiformis were subjected to rapid soil drying, respectively, as soil water content （SWC） decreased from the normal level ( 0.2.5 g·gDW-1) to 0.02 and 0.06 g·gDW-1, separately, plant water potential （ ψ ）dropped to - 4 and - 3.2 MPa, differently, the ATP in roots decreased 99.7% and 42%, respectively. When the rapidly dried soil was watered for up to 6 d, SWC and ψ, were found to recover to their normal levels, but ATP content in roots of P. orientalis and A. auriculiformis recovered by 10% and 23%, respectively. When plants

白桦木质部汁液产量及组分变异规律解析

白桦汁液采集时间大多在早春阶段,容易采集且产量高,为探讨温度对白桦木质部汁液变化的影响及不同发育时期汁液组分质量浓度的变化,以黑龙江省东北林业大学帽儿山实验林场白桦天然次生林为研究对象,通过收集2022年和2023年的白桦汁液,统计春季汁液流量。对2023年白桦不同发育时期汁液中的碳水化合物、氨基酸、总三萜、可溶性蛋白、pH以及钾、钙、钠、镁离子质量浓度进行分析,解析汁液组分变异规律。通过连续2 a取汁的白桦与当年取汁的白桦汁液组分质量浓度对比分析,探索连续取汁是否对白桦生长发育产生影响。结果表明,白桦汁液在4—6月中产量整体呈现先增后降的趋势,高峰期集中在4—5月份,且温度的升高会促进产汁。白桦木质部汁液的总三萜、碳水化合物、氨基酸、蛋白质组分质量浓度在整个物候发育时期均呈现先升后降再升的趋势,均在旺盛生长期时达到最低值。随物候发育白桦汁液pH整体呈下降趋势,在完全展叶前不断酸化。离子质量浓度整体呈先上升后下降的趋势。持续取汁不会对白桦汁液中总三萜、氨基酸、蛋白质质量浓度造成显著影响,会使碳水化合物质量浓度及pH降低。研究结果可为黑龙江省东部山地白桦汁液的科学采集提供指导依据。

Transport of Nitrogen Assimilation in Xylem Vessels of Green Tea Plants Fed with NH_4-N and NO_3-N

An experiment was carried out to study the transport process of nitrogen （N） assimilation from tea roots by monitoring the dynamic composition of N compounds in xylem sap after 15^N-NO3 and 15^N-NH4 were fed to the root of tea plants （Camellia sinensis L.）. Results showed that the main amino acids were glutamine, theanine, axginine, asparic acid and glutamic acid, which accounted for 49%, 17%, 8%, 7%, and 4%, respectively, of the total amino acids in the xylem sap. After the tea plants were fed with 15^N-NO3 and 15^N-NH4 for 48 h, the amount of total amino acids in xylem sap significantly increased and those fed with 15^N-NH4 had higher increment than those with 15^N-NOa. Two hours after 15^N- NO3 and 15^N-NH4 were fed, 15N abundance in glutamine, asparagine, glutamic acid, alanine, and arginine were detected and increased quickly over time. This indicated that it took less than 2 h for NO3-N and NH4-N to be absorbed by tea roots, incorporated into the above amino acids and transported to the xylem sap. Rapid increase in 15^N-NO3 in the xylem sap of tea plants fed with 15^N-NO3 indicated that nitrate could be directly transported to the xylem sap. Glutamine, theanine, and alanine were the main amino acids transported in xylem sap of tea plants fed with both 15^N-NO3 and 15^N-NH4.

水稻木质部伤流液响应镉胁迫的蛋白组鉴定

【目的】镉(Cd)的长距离转运决定了水稻对Cd的积累能力,木质部是这一过程的重要场所,鉴定木质部伤流液中参与Cd运输过程的蛋白质组,可以为水稻Cd积累调控提供理论基础。【方法】水培试验供试材料包括野生型水稻ZH11,野生型拟南芥Col-0,以及带有CAB2启动子驱动CAL1(Cd-accumulation in leaf 1)表达的拟南芥转基因植株CDM-4和CDM-12。水稻幼苗在Yoshida水稻营养液(Yoshida solution)生长28天后,转入含有0、10μmol/L Cd的营养液中处理3天,利用根压法收集木质部伤流液,对所得伤流液进行蛋白组质谱鉴定。将拟南芥材料进行了水培试验及平板试验,水培试验方法为拟南芥幼苗在1/4 PNS营养液(plant nutrient solution)中培养20天后,用10μmol/L Cd处理3天,测定Cd含量、植株生物量以及基因表达量;平板试验方法为拟南芥幼苗在0、50μmol/L Cd的1/2 MS平板上培养生长14天后,进行表型鉴定拍照。【结果】在Cd处理与正常条件所得水稻的木质部伤流液中共检测到616个蛋白,分子量在6~158.1 KDa。正常条件下鉴定到463个蛋白,Cd处理条件下鉴定到503个蛋白,其中有153个蛋白属于Cd处理所特异存在,这些Cd特异蛋白分别与植物抗氧化胁迫、细胞壁代谢和发育等相关,包括鉴定到的植物防御素CAL1蛋白,已有其参与Cd长距离转运的报道。在拟南芥地上部异源特异表达CAL1基因增加了地上部Cd的积累量,而对Cd耐受性没有显著影响,表明CAL1基因在植物修复土壤Cd污染过程中具有一定的应用前景。RNA-Seq分析了水稻苗期木质部伤流液Cd特异蛋白中与细胞壁代谢相关的基因的表达模式,这些基因对水稻Cd积累耐受的影响仍需进一步研究。【结论】通过对水稻木质部伤流液蛋白组的分析,鉴定了Cd处理条件下水稻木质部伤流液特异存在的蛋白组,为Cd的长距离转运提供了新的研究基因。

ALA Altered ABA Content of Winter Oilseed Rape(Brassica napus L.)Seedling

[Objective] The paper was to explore the impact of 5-aminolevunic acid（ALA）treatment on growth of winter oilseed rape（Brassica napus L.）seedlings and its mechanism.[Method] The effects of ALA on abscisic acid（ABA）contents in plant organs and xylem saps were investigated through hydroponic experiment.Four treatments including seed soaking with 0,25,50 and 75 mg/L ALA solutions（CK,A1,A2 and A3）for 6 h were set in the test.[Result] In addition to A3 treatment which made the dry weights of oilseed rape seedlings slightly decrease,after seed soaking with ALA,dry weights,net photosynthetic rate（Pn）,transpiration rate（Tr）and stomatal conductance（Gs）of plants significantly increased compared with control.ABA concentrations in plant shoots and xylem saps increased in different levels after seed soaking with ALA.[Conclusion] The increasing endogenous ABA contents might be an explanation for promotion effect of ALA application on the growth of winter oilseed rape seedling.

不同水、氮条件对水稻苗生长及伤流液的影响

为探明不同水分供应和氮素形态对水稻根苗及伤流液的影响,没正常水分及50 g/L PEG模拟水分胁迫和3种不同质量比例的NH_4^+-N/NO_3^--N(9/1、5/5、1/9)氮素营养处理,测定了水稻幼苗生物量,根系形态指标,根系活力及根基伤流量。结果表明,正常水分条件下,NH_4^+-N促进水稻根系平均直径增大,有利于水稻地上部物质累积;NO_3^--N则使水稻根系总吸收面积增大,促进根系物质累积;NH_4^+-N/NO_3^--N为5/5处理的水稻活跃吸收面积最大,活跃吸收面积比亦最高。水分胁迫条件下,NH_4^+-N/NO_3^--N为5/5的处理更有利于水稻地上部分的生长,NO_3^--N有利于水稻鲜重和干重增加,促进根系平均直径增大,水稻的根系总吸收面积、活跃吸收面积均随NO_3^--N供应比例的增加呈上升趋势。正常水分条件下,水稻幼苗白天的耗水量随NH_4^+-N/NO_3^--N比例降低呈下降趋势,水分胁迫条件降低了水稻对水分的吸收。水分胁迫显著降低各处理水稻伤流量,正常水分条件下,NH_4^+-N/NO_3^--N为5/5处理的水稻伤流量最大;水分胁迫后,9/1处理的水稻伤流量相对较多。

30%己乙水剂对玉米根系伤流液及其组分的影响

以玉米 3138为材料 ,在大田和 PVC管栽条件下研究了应用植物生长调节剂 30 %己乙水剂对玉米根系伤流量、伤流中无机离子流量、氨基酸组分及流量、激素流量等的影响 ,结果表明 :30 %己乙水剂可提高玉米根系伤流量 ,特别是大喇叭口期和籽粒形成期 ;提高了伤流中 K,P,Ca,Mg,Si,Zn,Mn,Fe,B,Mo,Cu等无机元素流量 ,氨基酸总流量提高 ,主要的运输形式氨基酸 Ser,Glu,L ys,Arg,Val,Ala,L eu,Ile,His,Try,Phe流量均明显增加 ,非蛋白质氨基酸 GAba大幅度增加 ,伤流液中 IAA在籽粒形成和灌浆期提高 ,授粉后伤流中 Gas提高 ,CTKs在籽粒形成期提高 ,ABA在灌浆期提高 ,吐丝前低于对照 .表明 30 %己乙水剂可促进根系吸收和合成物质向地上部分的输送 ,对促进地上部发育有重要作用 .

硅对向日葵水分利用效率的影响

以向日葵(HelianthusannuusL.cv.G101)为试验材料,研究了硅对营养液培养的向日葵生长和水分利用效率的影响。结果表明,施硅显著增加向日葵的水分利用效率,对向日葵生物量、叶面积的影响不大,却使最大展开叶的SPAD值显著增加;施硅显著降低了向日葵叶片背面的蒸腾速率以及叶片导度,而对叶片正面的蒸腾速率和叶片导度影响不大。同时,施硅向日葵木质部汁液的流速显著降低,体内硅含量增加。表明叶片蒸腾速率、叶片导度、木质部汁液流速的降低是硅提高向日葵水分利用效率的主要原因。

根际通气对基质气体、肥力及黄瓜伤流液的影响

为改善根际气体环境,试验采用基质通气栽培方式,研究不同通气方式对基质气体、肥力及黄瓜伤流液的影响。结果表明,基质底部通气和基质上部通气均显著改善根际二氧化碳和氧气体积分数,二氧化碳体积分数比对照降低33.31%～98.02%,氧气体积分数比对照提高2.13%～12.22%。通气处理显著提高基质速效养分质量分数,碱解氮比对照提高12.95%～28.87%,速效磷比对照提高12.02%～20.46%。基质上部通气处理的伤流液流量、电导率值和伤流液氨基酸含量均最高,表明基质上部通气处理根系代谢旺盛,是较理想的基质通气方式。

不同供氮模式对水稻根系形态及生理特征的影响

【目的】为明确氮素优化管理模式(OPTs)下水稻根系形态和生理特征及其与氮素吸收和产量形成的关系。【方法】以镇稻11为材料,采用营养液培养,通过三种氮素供应模式分别模拟农民习惯施肥(FFP)、高效施肥(HE)及高产高效施肥(HEHY),研究了不同供氮模式对水稻主要生育期生物量和氮素累积、根系形态和生理特征以及产量形成的影响。【结果】与FFP相比,HE和HEHY(OPTs)通过提高每穗粒数、结实率和千粒重而使水稻籽粒产量分别增加5.7%和16.0%。与FFP相比,OPTs增加了生育期内水稻根系生物量、根系长度、根系总表面积、根系体积以及单个分蘖不定根数目,并提高了灌浆期根系活力、根系氮素同化能力以及叶片光合速率。相关分析表明,开花期根系生物量、总表面积、根体积、单个分蘖平均不定根数目、伤流液流速和谷氨酰胺合成酶活性均与总氮素累积量及产量显著正相关。【结论】因此,OPTs通过养分调控,可促进水稻根系的生长、优化根系形态结构,并能维持水稻生育后期较高的根系活力,从而促进了水稻对氮素的累积以及产量的形成。

番茄根系分泌物、木质部和韧皮部汁液组分对矿质氮和有机氮营养的响应

采用营养液水培方法探讨了番茄幼苗根系参数、根系分泌物、木质部和韧皮部汁液组分对矿质氮(NH_4^+-N、NO_3^--N)和有机氮(Glycine)的不同响应。结果表明,不同氮素处理8 d后,‘申粉918’、‘沪樱932’番茄根系干质量、特系体积表现为No_3^--N>GIy-N>对照>NH_4^+-N处理;而根系活力则表现为以供Gly-N或NO_3^--N为最高,其次为供NH_4^+-N的处理,对照处理最低。不同氮素形态显著影响不同番茄品种根系分泌物、木质部和韧皮部各组分含量。NO_3^--N处理的番茄根系分泌物、木质部和韧皮部汁液中的NO_3^--N和P含量最高,供Gly-N、NH_4^+-N其次,对照最低;而供Gly-N、NH_4^+-N时铵态氮、游离氨基酸、可溶性糖含量一般均高于处理No_3^--N和对照。番茄根际吸收不同氮素对根际pH亦产生不同的影响,吸收NO_3^--N和Gly-N后,根际pH显著升高,而吸收NH_4^+-N后则降低。根系分泌物可溶性蛋白含量的变化表现为NO_3^--N>Gly-N>NH_4^+-N>对照,而木质部、韧皮部可溶性蛋白含量的变化则表现为Gly-N>NO_3^-N>NH_4^+-N>对照。番茄幼苗不同品种间的差异性表现,与氮素形态有关,以根系活力为指标的基因型差异在供应No_3^--N、NH_4^+-N和Gly-N及对照时,‘沪樱932’的根系活力均显著(P<0.05)大于‘申粉918’。

氮素形态及水分胁迫对水稻根系生理特性的影响

采用室内营养液培养、聚乙二醇(PEG 6000)模拟水分胁迫的方法,在3种供氮形态下(NO3--N、NH4+-N和NO3--N与NH4+-N等体积混合),研究了在非水分胁迫及模拟水分胁迫(添加10%PEG,约相当于-0.15 MPa)下,苗期水稻根系的生长状况、水分吸收状况及木质部汁液特性。结果表明,水分胁迫抑制了供NO3--N营养水稻根系的生长,而对供NH4+-N水稻根系的生长没有影响;水分胁迫提高了NH4+-N营养水稻木质部汁液pH值,并增加其渗透势。提示:水分胁迫条件下,NH4+-N营养对根系生长及木质部汁液调节可能是氮素增强水稻抗旱性的原因之一。

大气CO_2浓度升高对水稻伤流液中矿质元素的影响

利用中国的稻/麦轮作FACE平台技术,用伤流液的方法研究了在低氮和常氮两种水平下,大气CO2浓度升高对水稻在分蘖期、抽穗期和乳熟期的伤流量及其伤流液中矿质元素的影响,并阐述在FACE条件下,植物对矿质元素吸收的差异。结果表明,在分蘖期和乳熟期,FACE和N肥处理对伤流量没有显著性的影响;在抽穗期,FACE处理明显高于对照。FACE处理降低了伤流液中Ca、Mg、Si的浓度,但却增加了P的浓度,对K、Mn、Zn没有显著性的影响。在抽穗期,FACE处理显著增加了Ca、Mg、P、K和Mn在单位时间段内的吸收量;在分蘖期和乳熟期,FACE处理对Ca、Mg和Si的吸收量却有降低的趋势。

镉污染对水稻不同生育期生长和品质的影响

通过盆栽试验,研究了在CK、5、10和20mg·kg-14个不同镉处理浓度下,水稻生长发育农艺指标和部分品质指标的变化,同时分析了不同生育期水稻根系活力和伤流液中镉含量的变化规律。结果表明,淹水条件下,镉对水稻产生生育障碍的浓度比较高。土镉20.84mg·kg-1时,水稻的经济产量减产超过10%,同时,糙米中直链淀粉的含量也显著增加。当土壤镉含量为4.48mg·kg-1时,糙米中镉含量显著增加而蛋白质含量显著减少。在水稻不同的生长发育期,根系活力与伤流液中镉的含量表现出相同的变化趋势。伤流液中镉在营养生长阶段吸收最大,且与土壤中的镉呈线性关系。

耐盐性不同的小麦根和根茎结合部的拒Na^+作用

NaCl处理引起小麦幼苗干重下降 ,盐敏感品种比耐盐品种下降幅度要大。盐敏感品种的拒Na+ 能力为 35 %左右 ,耐盐品种的拒Na+ 能力为 5 0 %～ 6 0 %左右 ,这表明耐盐品种的拒Na+ 能力远远大于盐敏感品种。不同耐盐性小麦的拒Na+ 部位不同 ,盐敏感品种的拒Na+ 部位主要在根茎结合部 ,而耐盐品种的拒Na+

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以黄瓜品种津优30为试材,以玉米秸秆∶牛粪∶炉渣=3V∶1V∶1V为栽培基质,分别采用底部(透水、不透水)编织袋、无纺布和双色膜为4种栽培袋材料,进行日光温室黄瓜营养基质袋式栽培试验,研究了不同栽培袋材料对黄瓜植株生长、伤流液、产量和品质的影响。结果表明:采用底部不透水编织袋为栽培袋材料时,定值后40d及55d黄瓜的株高显著高于其他3个处理,并且其植株地上部鲜质量、地下部干质量、黄瓜伤流液中养分含量也显著高于其他3个处理,果实可溶性蛋白、VC含量都高于其他处理。因此,底部不透水编织袋是适宜黄瓜袋培的栽培袋材料。