Plant–soil feedback effects on the performance and functional traits of Dodonaea viscosa in a dry-hot valley,China

Plant–soil feedback has been widely studied and may be particularly important in resource-poor areas. However, the roles of direct and indirect biotic effect in affecting plant growth and functional traits in this process still remained unclear. The aim of this study was to explore the roles of soil biota in affecting plant performance and traits by conducting a two-phase feedback experiment in a dry-hot valley, with a conditioning phase during which there were Dodonaea viscosa or no D. viscosa growing in the soil and a feedback phase in which the effect of the conditioned soil biota on D. viscosa performance was measured. Soil N was reduced by the presence of D. viscosa during the conditioning phase. However, D. viscosa showed a positive plant–soil feedback. In the feedback phase, the D. viscosa-conditioned soil increased the stem diameter, total biomass, and leaf dry mass content of D. viscosa, while the specific leaf area was significantly lower in D. viscosa-conditioned soil than that in bare soil. In contrast, soil sterilization had a negative effect on the growth of D. viscosa, with a significant reduction in biomass, especially in D. viscosa-conditioned soil, and soil sterilization significantly increased the root:shoot biomass ratio and litter mass. Furthermore, we showed that although the biota-driven changes in enzyme activities correlated with leaf N and especially P amount, the enzyme activity was not the main reason to promote D. viscosa growth in conditioned soil. These results suggest that the positive biotic feedback effect was superior to the negative nutrient-depleted effect on D. viscosa growth, and the direct biotic feedback effect would drive the positive effect of soil biota to a greater extent than the indirect effect. The positive biotic plant–soil feedback in dry-hot valley plays an important role in ecosystem restoration and helps in understanding plant adaptation to the local environment in this area.

     

Impact of orientation and flexibility of peptide linkers on <Emphasis Type="Italic">T. maritima</Emphasis> lipase Tm1350 displayed on <Emphasis Type="Italic">Bacillus subtilis</Emphasis> spores surface using CotB as fusion partner

Fusion protein construction often requires peptide linkers for prolonged conformation, extended stability and enzyme activity. In this study a series of fusion between Thermotoga maritima lipase Tm1350 and Bacillus subtillis coat protein CotB, comprising of several peptide linkers, with different length, flexibility and orientations were constructed. Effects of temperature, pH and chemicals were examined, on the activity of displayed enzyme. The fusion protein with longer flexible linkers L9 [(GGGGS)₄] and L7 (GGGGS-GGGGS-EAAAK-EAAAK-GGGGS-GGGGS) possess 1.29 and 1.16-fold higher activity than the original, under optimum temperature and pH respectively. Moreover, spore surface displaying Tm1350 with L3 (EAAAK-GGGGS) and L9 ((GGGGS)₄) showed extended thermostably, maintaining 1.40 and 1.35-fold higher activity than the original respectively, at 80 °C after 5 h of incubation. The enzyme activity of linkers with different orientation, including L5, L6 and L7 was determined, where L7 maintained 1.05 and 1.27-fold higher activity than L5 and L6. Effect of 0.1% proteinase K, bromelain, 20% ethanol and 30% methanol was investigated. Linkers with appropriate Glycine residues (flexible) showed higher activity than Alanine residues (rigid). The activity of the displayed enzyme can be improved by maintaining orientation and flexibility of peptide linkers, to evaluate high activity and stability in industrial processes.     

水分和种植密度对干热河谷车桑子生长性状及种内相互关系的影响

水分是干热河谷植物生长过程中最主要的限制因子,种植密度增加也会引起植物生长的资源限制,两者交互作用下植物生长性状及种内关系的变化特征还不清楚。以干热河谷优势植物——车桑子为研究对象,根据元谋干热河谷年均生长季降雨量设置3种水分梯度:高水分、中水分和低水分,同时在各水分梯度下设置4个种植密度:1、2、4、9株/盆,探究水分、种植密度及其交互作用对车桑子生长性状、生物量分配及种内相互作用的影响。结果表明:(1)低水分条件下,车桑子生长和水分生理受到抑制,但车桑子在较低的叶水势下依然能够保持较高的相对含水量;(2)干旱胁迫显著降低了车桑子总生物量和单株生物量,显著增加了枯叶生物量比例,低水分和中水分条件下,增加种植密度对总生物无显著影响;而高水分条件下,增加种植密度显著提高了车桑子总生物量;(3)低水分显著增加了茎、叶生物量的异速生长指数,将更多生物量分配到叶,而种植密度增加显著降低了茎、叶生物量的异速生长指数,增加了茎的生物量分配;(4)通过相对邻体效应的计算,各处理条件下,车桑子种内关系均表现为竞争作用,并且,这种竞争作用的强度随水分的减少和密度的增加而增加。在高密度条件下(9棵/盆),...     

干热河谷车桑子光合生理特性对氮磷添加的响应

氮磷养分是限制干热河谷植物生长的重要元素,不同土壤上植物受到的养分限制类型不同。光合作用作为植物生长发育的基础,不同土壤上氮磷养分添加对干热河谷植物光合生理特征的影响还没有报道。因此,以干热河谷优势植物——车桑子为研究对象,在元谋县不同海拔处采集土壤,设置加氮（+N）、加磷（+P）、氮磷同时添加（+NP）和不添加（CK）四个处理,研究车桑子光合响应曲线、叶绿素含量和叶绿素荧光特性对氮、磷添加的响应规律,并探讨光合响应特征与车桑子生长的关系：研究结果显示：1）不同海拔土壤上,车桑子光合生理特性对氮磷添加具有不同的响应。在低海拔燥红土上,氮添加处理（+N和+NP）提高了车桑子净光合速率、叶绿素含量和PSII活性;中海拔紫色土上,+NP促进了车桑子光合速率和叶绿素含量的提高;高海拔黄棕壤上,+N处理降低了车桑子净光合速率和PSII活性,而磷添加处理（+P和+NP）提高了车桑子净光合速率。2）车桑子光合特性对养分添加的响应取决于土壤的养分限制类型,限制性养分添加可以提高车桑子的净光合速率。3）燥红土上+P以及黄棕壤上+N对PSⅡ最大光化学效率（Fv/Fm）的降低更大程度上归于可变荧光Fv的减少而不是最小荧光F₀的增加,可减少养分限制对光系统II造成的伤害。4）三种土壤类型上车桑子的叶绿素含量和组成差异极显著,相比于燥红土和紫色土,黄棕壤上车桑子的叶绿素含量显著更高,而叶绿素a/b显著更低。综上,本研究结果表明,车桑子光合能力受到氮和磷的共同调节,不同土壤上光合生理特性的响应可增强植物对限制性养分的适应性,影响植物生长发育。     

不同土壤和微量元素对车桑子幼苗生长的影响

为了解微量元素对车桑子(Dodonaea viscosa)生长的作用,研究添加微量元素(硼B、铁Fe、锰Mn、锌Zn)对车桑子生长和叶绿素荧光特性的影响。结果表明,除Mn外,B、Zn和Fe均对车桑子的生长和叶绿素荧光参数有显著促进作用(P<0.05);且添加B的车桑子具有更高的生物量积累,比对照显著提高了133.61%。微量元素与土壤类型对叶片磷(P)含量和叶片氮磷比(N/P)具有显著的交互作用(P<0.05),紫色土添加Zn、黄棕壤添加Fe均显著降低了叶片N/P。燥红土和黄棕壤上车桑子的株高、叶面积和生物量积累均高于紫色土,但紫色土和黄棕壤上车桑子的根冠比和叶片N/P显著高于燥红土(P<0.001)。这表明微量元素对干热河谷车桑子生长具有重要作用,在植被恢复过程中可通过添加B、Fe、Zn尤其是B来促进植物生长。     

Temperature and soil microorganisms interact to affect <Emphasis Type="Italic">Dodonaea viscosa</Emphasis> growth on mountainsides

There is considerable interest in understanding the drivers of plant growth in the context of climate change. Soil microorganisms play an important role in affecting plant growth and functional traits. However, the role of interaction between soil microbes and temperature in affecting plant growth and functional traits remains unclear. The objective of this research was to investigate the effects of soil microbes, temperature, and their interaction on the growth and functional traits of Dodonaea viscosa in a mountain in Yuanmou county, southwest China. The experiment was conducted in climate chambers with a factorial design of three soil microbial communities (inoculated rhizosphere microbes from high elevation, inoculated rhizosphere microbes from low elevation, and autoclaved control) and two temperature conditions (colder and warmer). D. viscosa planted in inoculated rhizosphere microbes from both high and low elevations produced more total biomass with a lower root–shoot allometric exponent, and accumulated significantly more N and P nutrients than those in an autoclaved control, with no significant differences between the two microbial inoculations. Thus, rhizosphere soil microorganisms had positive effects on D. viscosa growth. However, the effect of the microbes on plant growth strongly depended on temperature. Warming had a positive effect on D. viscosa growth in inoculated rhizosphere microbe treatments, while the positive effect disappeared in the autoclaved control treatment. Our results indicate that temperature and soil microorganisms interact to affect D. viscosa growth. As the climate changes in the future in the studied region, the growth of D. viscosa may be greatly affected both directly and indirectly through the temperature–soil microbe interaction.     

金沙江干热河谷植物叶片元素含量在地表凋落物周转中的作用

叶片的化学计量学特征在植物响应环境变化,决定植物的生后效应中具有重要的偶联作用。为了阐明植物叶片生源要素含量对凋落物周转的影响,分析了金沙江干热河谷萨瓦纳草地生态系统植物叶片的化学计量学特征与凋落物周转时间的关系。结果显示:凋落物周转受到多重生源要素及其交互作用的影响,其中K与凋落物周转时间存在显著的正相关关系,而S、Mn、Mg元素具有负关系,表明K可能抑制凋落物的分解,而S、Mn、Mg元素可能会促进凋落物分解。在物种水平上K、S、Mn分别与凋落物周转时间存在显著的相关性, K、S组合解释了16.93%的凋落物周转时间变异;样方水平上,K、S、Mn、Mg分别与凋落物周转时间具有显著相关性,虽然N对凋落物的周转时间影响不显著,但当N与K及其交互作用对凋落物周转时间解释了37.42%的变异。其它元素组合也可在不同程度上解释了凋落物周转时间的变异。多元要素的互作效应表明元素间可能存在拮抗和协同效应,凋落物分解过程中可能受到多重分解者的共同作用,而不同分解者会受到不同的元素限制。未来的研究应当注重N、P以外的元素在生物地球化学循环中的作用。     

Alternating current-assisted on-plate proteolysis for MALDI-TOF MS peptide mapping

In this report, alternating current-assisted on-plate proteolysis has been developed for rapid peptide mapping. Protein solutions containing trypsin were allowed to digest directly on the spots of a stainless steel MALDI plate with the assistance of low-voltage alternating current electricity. Alternating current (AC) was allowed to pass through the protein solutions via the MALDI plate and a platinum disc electrode. The feasibility and performance of the novel proteolysis approach were investigated by the digestion of BSA and cytochrome c (Cyt-c). It was demonstrated that AC substantially enhanced the efficiency of proteolysis and the digestion time was significantly reduced to 5 min. The digests were identified by MALDI-TOF MS with sequence coverages of 42% (BSA) and 77% (Cyt-c) that were comparable to those obtained by using conventional in-solution tryptic digestion. The present proteolysis strategy is simple and efficient, offering great promise for MALDI-TOF MS peptide mapping.     

干热河谷土壤酶活性对碳氮添加的响应

碳氮是生态系统物质循环中的关键元素,然而碳氮对土壤生态系统功能是否具有交互作用还缺乏深入研究。通过干热河谷土壤的葡萄糖和硝酸铵的交互添加实验,研究了氮、碳添加及其交互作用对干热河谷土壤酶活性及其化学计量学特征的影响。结果表明:碳氮交互作用显著影响了葡萄糖苷酶、酸性磷酸酶和亮氨酸胺肽酶活性。在对照样方的土壤中,碳添加使葡萄糖苷酶活性降低了31.4%;在施氮样方的土壤中,碳添加使葡萄糖苷酶活性增加了54.4%。对照样方中的土壤中,碳添加对酸性磷酸酶和亮氨酸胺肽酶活性促进作用较小(分别增加了102.4%和28.8%);相比之下,在施氮样方的土壤中,碳添加使酸性磷酸酶和亮氨酸胺肽酶活性分别增加了302.2%和68.8%。碳添加对葡萄糖苷酶和酸性磷酸酶活性的促进作用与土壤初始有效氮含量显著正相关。几丁质酶活性在碳添加下增加了53.7%,对氮添加没有响应。碳氮交互作用也显著影响了C∶N和C∶P的水解酶化学计量关系。在对照样方中碳添加使C∶N水解酶化学计量比降低了16.9%,C∶P水解酶化学计量比降低了19.9%;而在施氮样方土壤中,碳添加的影响较小C∶N和C∶P水解酶化学计量比分别降低了1.9%和5.8%。碳氮交互作用对干热河谷土壤酶活性的影响表明碳氮在土壤生态系统功能具有重要作用。