有机物通过茎中韧皮部向下运输——环割实验

有机物通过茎的韧皮部向下运输,如果在茎或枝条上进行环割使运输途径中断,有机物就会聚集在其上方,引起这部分组织生长加剧,而形成肿大的愈伤组织即树瘤;或是影响枝条中断以下部分不定根(其生长与有机物有关)的形成及生长,借此证明有机物运输的途径。     

环剥对红松(Pinus koraiensis)韧皮部和木质部碳水化合物的影响

树干环剥可以阻碍韧皮部光合产物的运输并进一步影响光合产物的分配。长时期内,环剥能够导致环痕上部可溶性糖和淀粉的积累,但对于短期内如何影响碳水化合物在木质部和韧皮部内的运输模式所知甚少。以38年生红松(Pinus koraiensis Sieb.etZucc.)为研究材料,分别对环剥上部、下部每隔1~2d采样,区分木质部和韧皮部(树皮)进行可溶性糖和淀粉含量及树干糖呼吸消耗速率测定,确定环剥后的日变化和周变化,并对木质部可溶性糖、淀粉含量与韧皮部中相应指标进行相关关系的回归分析。结果发现:(1)环剥后4周内,在环剥痕上、下部间木质部可溶性糖和淀粉含量,韧皮部中淀粉含量均不存在显著差异(p>0.05),而韧皮部内可溶性糖含量,环剥后第2周出现显著差异,从第4周出现环剥上部显著高于下部的碳水化合物积累现象(p<0.05);(2)环剥阻隔了韧皮部可溶性糖的纵向运输,但是并不影响木质部的纵向运输,而且环剥并没有影响木质部和韧皮部之间的糖和淀粉的相关关系;(3)环剥第1周内环剥上部和下部呼吸消耗速率差异不显著,第2周环剥上部显著高于环剥下部,从第3周开始环剥下部呼吸消耗速率显著下降。推断认为,在环剥处理的4周内,环剥上部冠层新形成的碳水化合物很大一部分均被呼吸消耗掉,导致环剥上部较环剥下部可溶性糖稍有增加;红松胸高直径以下部分所储藏的碳水化合物足以保障2周内红松树干呼吸。     

暹罗苏铁茎的解剖学研究

利用冰冻切片法在光学显微镜下观察暹罗苏铁茎的解剖特征。结果表明,暹罗苏铁茎由周皮、皮层、皮层维管束、中柱和髓组成,皮层和髓发达。皮层维管束可分为周韧型和外韧型两种,以周韧型为主。中柱的次生结构为同心环的次生维管组织构成,随着茎的不断成熟,环数逐渐增加;每个同心环均含有次生木质部、维管形成层、次生韧皮部的结构;环与环之间有次生的薄壁组织相间隔。皮层、中柱维管束均由木质部、形成层和韧皮部组成,木质部面积均大于韧皮部。苏铁植物茎在次生结构方面的主要特点是有皮层维管束和同心环结构的中柱维管束。     

植物韧皮部的结构与功能

韧皮部一般与木质部相联合,构成维管植物的维管系统。它也和木质部一样是由多组织所组成的复合组织。“韧皮”一名称显然是因为这部分组织往往含有抗拉性强的纤维而得名,但抗拉性并不是韧皮部的主要功能,而且有些植物的韧皮部中不含有纤维,故也就没有这种功能。韧皮部主要功能是有机物质的运输。自从1837年哈蒂格(Hartig)在韧皮部中发现筛管以后,一般都认为筛管是一长距离运输有机物的组织结构。但在早期的实验都是采取茎环割的方法,这种方法所割去的组织除去韧皮部外还有皮层和形成层,因此并不能明确地证明物质运输是韧皮部,更不能证明是筛管。1930年舒马希尔(schumacher)用天竺葵属     

环剥和去叶对红松雌球果和枝生长及不同组织和器官中养分含量的影响

为探索红松雌球果发育和新枝生长的养分来源和供需关系,对生殖母枝进行环剥、去叶及两者相结合处理,研究不同处理对雌球果发育和枝生长及不同组织和器官中碳水化合物(NSC)、氮(N)和磷(P)含量的影响.结果表明:环剥处理对雌球果发育和新枝生长及不同组织和器官中NSC、N和P含量影响显著,去叶处理的影响较小.环剥后母枝木质部和韧皮部NSC含量显著低于对照(CK,不环剥+0%去叶),并随去叶程度的增加显著减少,尤其是环剥+100%去叶的木质部和韧皮部中NSC含量分别比CK减少59.0%和64.8%,NSC的不足导致母枝、新枝死亡和雌球果败育.环剥处理下,0%、50%和100%去叶处理的母枝木质部和韧皮部中N和P含量显著高于CK,其中木质部中N含量比CK分别高17.3%、18.2%和24.3%,P含量比CK分别高17.9%、7.1%和3.6%,韧皮部中N含量比CK分别高39.3%、35.2%和48.9%,P含量比CK分别高31.0%、28.2%和14.8%.红松雌球果发育和新枝生长消耗大量的碳水化合物、N和P,母枝本身制造或贮存的碳水化合物和矿质养分不能满足雌球果发育和新枝生长的需求,碳水化合物和矿质养分需要从母枝以外的其他组织输入.     

有机物输导实验的改进

有机物输导的实验,许多书中都是环剥树枝、观察割口上部产生的瘤状突起。此法操作简便,效果明显,但实验期长（通常需要数月至一年才能突出明显效果）,而且学生容易产生有机物只能由上向下输导的误解。为此,我们在教学中选用木本植物花期环剥,观察花的变化,进行探索...     

叉孢苏铁茎的解剖学研究

对叉孢苏铁茎的解剖结构进行了仔细的研究,结果表明:叉孢苏铁茎具有发达的皮层,皮层及髓中具有黏液道,有外韧型和周韧型的维管束分布在皮层中,但主要以外韧型为主,在同一切面上能看到横、纵、斜3种不同走向的维管束,所有皮层维官束韧皮部组成成份比较单一。维管组织区由多个生长环组成,每个生长环都具有木质部、维管形成层和韧皮部组成,各生长环韧皮部所占比例均大于木质部,在具4生长环的下部茎的维管组织中,环与环之间间隔2～10层不等的薄壁细胞。从纵向变化上看,从上至下,维管组织区的厚度及生长环数逐渐递增,在同一组织中,含晶及含单宁物质的异细胞呈从无到有,从少到多的分布趋势。     

灵武长枣果实同化物韧皮部卸载和运输途径研究

韧皮部卸载和韧皮部后运输在调节同化物在果实中的分配和积累方面起着至关重要的作用,而且很大程度上决定着果实的产量和质量。为探讨灵武长枣果实同化物韧皮部卸载和运输途径,以4个时期灵武长枣果实为实验材料,对各个发育时期果实维管束的显微结构进行观察,并综合运用荧光染料活细胞示踪与激光共聚焦扫描显微镜技术实时观察果实内韧皮部同化物卸载路径的变化,为灵武长枣果实同化物积累和品质调控奠定基础。结果显示：(1)膨大前期不仅果实的韧皮部中具有明显的CF绿色荧光,同时在周围薄壁细胞中也分布着CF绿色荧光,筛管伴胞复合体和周围薄壁细胞之间存在着共质体联系。(2)快速膨大期,CF绿色荧光主要局限于果实的韧皮部中,在韧皮部周围薄壁细胞中分布较少,筛管伴胞复合体与周围薄壁细胞之间主要以共质体隔离为主,但也存在着一定的共质体联系。(3)着色期和完熟期,CF绿色荧光局限于果实的韧皮部中,在韧皮部周围薄壁细胞中基本没有CF绿色荧光,果实筛管伴胞复合体与周围薄壁细胞之间是共质体隔离状态,但引入CFDA的同时引入具有质膜通透作用的洋地黄皂苷时,周围薄壁细胞中CF绿色荧光分布明显增加。研究认为,灵武长枣在膨大前期果实韧皮部同化物为共质体卸载途径,快速膨大期果实主要以质外体途径运输同化物,但也通过共质体卸出同化物,着色期和完熟期果实通过质外体途径运输同化物。     

鸭儿芹不同器官分泌道结构及分布的比较解剖研究

采用石蜡切片法对伞形科鸭儿芹(Cryptotaenia japonica Hassk. )全株不同器官分泌道的结构及分布特征进行了观察研究.观察结果显示,在鸭儿芹的根、茎、叶和果实各部位均有分泌道,其中果实分泌道特化为油管.分泌道多由1层明显小于周围薄壁细胞的分泌细胞组成,不同器官中分泌道的管腔和分泌细胞均大小不等、形状不一.组成根中分泌道的分泌细胞较少,多为4～5个;茎中较多,为6～9个,有时多达12～14个;组成叶片分泌道的分泌细胞数差异最大,叶脉中多达22个,叶肉中仅为3个.从横切面上看,根系中的分泌道仅分布在主根和一级侧根的近周皮处,以及主根的韧皮部外侧和髓部;茎中分泌道分布于近表皮处的厚角组织之间、大厚角组织与韧皮部之间和靠近木质部的髓部;叶鞘和叶柄的分泌道位于小厚角组织内侧的顶端、大厚角组织与韧皮部之间和木质部周围,其中在叶鞘中的2个厚角组织之间也有分泌道分布;在叶片的主脉及大侧脉中,分泌道分布于维管束与上下表皮的厚角组织之间,栅栏组织中也有少量分泌道;在果实中,油管分布于内果皮与中果皮之间,多位于棱槽和合生面部位.此外,根和茎中的分泌道具有2种明显不同的分布式样;叶鞘远、近轴面部位分泌道的分布式样分别兼有茎近表皮皮层部位和叶柄维管束木质部部位的特点,具有明显的从茎向叶柄的过渡性;在果实的果棱维管束下方和2个油管之间还有2层油细胞几乎环果体分布,这种结构在伞形科种类中比较少见,值得进一步研究.     

漆树各器官中乳汁道的分布与结构特征研究

采用石蜡制片法,对漆树茎、根、叶、花、果实中乳汁道的分布与结构特征进行解剖学观察研究.结果表明,(1)除种子外,漆树的根、茎、叶、花和果实内均具有乳汁道,乳汁道主要分布在各器官维管束的韧皮部内,茎的髓部内也有少数分布.(2)乳汁道都是由一层分泌细胞及其外的多层薄壁鞘细胞围绕着腔道构成,属于贮存生漆的分泌道.(3)漆树不同器官内乳汁道的直径和鞘细胞的层数存在差异.     

非点源污染物在沟渠湿地中的累积和植物吸收净化

对有机质和总氮在沟渠湿地底泥中的垂直分布和水平分布的研究表明,40 cm以下深度的芦苇(Phragmites communis)和茭草(Zizania latifolia)湿地底泥对有机质和总氮有显著的持留和累积作用;但表层底泥中含量随季节变化大,最高与最低值相差近2倍以上.有机质和总氮之间有极显著的相关关系,在芦苇和茭草湿地底泥中的相关系数分别为0.9876和0.9335.水体中总氮与NH₄⁺-N和NO₃-N也显著相关,表明总氮的主要成分是有机氮,其矿化作用是无机氮的重要来源.每年秋季芦苇收割以后,可带走氮818 kg·hm^-2和磷103.6 kg·hm^-2,茭草可带走氮131 kg·hm^-2和磷28.9 kg·hm^-2.茭白对氮的吸收能力高,试验表明,利用茭白取代野生植物,既能取得很好的净化效果,又可被农民主动回收,解决植物的二次污染问题.     

Bacteria associated with yellow lupine grown on a metal‐contaminated soil: in vitro screening and in vivo evaluation for their potential to enhance Cd phytoextraction

In order to stimulate selection for plant‐associated bacteria with the potential to improve Cd phytoextraction, yellow lupine plants were grown on a metal‐contaminated field soil. It was hypothesised that growing these plants on this contaminated soil, which is a source of bacteria possessing different traits to cope with Cd, could enhance colonisation of lupine with potential plant‐associated bacteria that could then be inoculated in Cd‐exposed plants to reduce Cd phytotoxicity and enhance Cd uptake. All cultivable bacteria from rhizosphere, root and stem were isolated and genotypically and phenotypically characterised. Many of the rhizobacteria and root endophytes produce siderophores, organic acids, indole‐3‐acetic acid (IAA) and aminocyclopropane‐1‐carboxylate (ACC) deaminase, as well as being resistant to Cd and Zn. Most of the stem endophytes could produce organic acids (73.8%) and IAA (74.3%), however, only a minor fraction (up to 0.7%) were Cd or Zn resistant or could produce siderophores or ACC deaminase. A siderophore‐ and ACC deaminase‐producing, highly Cd‐resistant Rhizobium sp. from the rhizosphere, a siderophore‐, organic acid‐, IAA‐ and ACC deaminase‐producing highly Cd‐resistant Pseudomonas sp. colonising the roots, a highly Cd‐ and Zn‐resistant organic acid and IAA‐producing Clavibacter sp. present in the stem, and a consortium composed of these three strains were inoculated into non‐exposed and Cd‐exposed yellow lupine plants. Although all selected strains possessed promising in vitro characteristics to improve Cd phytoextraction, inoculation of none of the strains (i) reduced Cd phytotoxicity nor (ii) strongly affected plant Cd uptake. This work highlights that in vitro characterisation of bacteria is not sufficient to predict the in vivo behaviour of bacteria in interaction with their host plants.     

The effect of stem diameter on European corn borer behavior and survival: potential consequences for IRM in Bt-corn

The ability of non‐crop plants to support complete development of insect pests is an important factor for determining the impact of those plants on resistance management programs for transgenic crops. We assessed the effect of one physical factor, plant stem diameter, on the ability of plants to support full development of the European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), the target pest of transgenic Bt‐corn. In the field, European corn borer larvae were significantly more likely to tunnel and survive in plants with larger stem diameters. Larvae were 40× more likely to survive on corn, the largest plant tested, compared to many of the smaller plants. In the laboratory, larvae were more likely to survive in and less likely to abandon the largest diet‐filled artificial stems that varied only in stem diameter. In conditions simulating those that an ECB larvae would encounter upon abandoning a host, larvae survived up to three weeks and were able to locate corn as a new host with a significantly higher frequency than would be expected if they were foraging randomly. These results indicate that the probability of ECB larval survival to maturity on a plant other than corn is relatively low and thus these smaller stemmed non‐corn plants may not make a substantial contribution to the pool of susceptible adults. Conversely, since more mature larvae are not as susceptible as neonates, any larvae that partially develop on non‐corn plants and subsequently colonize Bt‐corn may not be exposed to a lethal dose of the toxin. Since some proportion of the individuals that survive could be partially resistant heterozygotes the presence of non‐corn host plants could facilitate the development of resistant ECB populations.     

Molecular divergence of alfalfa somaclones

Summary Plantlets were regenerated from alfalfa callus following passage through a tissue culture medium which contained gibberellic acid. A proportion of these plantlets showed obvious morphological variations. Leaflet, stem and petiole tissue of these plants were extracted to yield a soluble protein homogenate which was characterized by polyacrylamide gel electrophoresis. Over 18 individual protein bands were resolved and visualized by staining with coomassie blue G250. Electrophoretic gels from regenerated plantlets and from the parent plant were scanned spectrophotometrically and analyzed. The relative quantity of each of the proteins resolved from plants was correlated with proteins of other plants via the Pearson's product-moment correlation. Cluster analysis was then performed using these correlation coefficients to judge relatedness among somaclones and the parent plant. Two of 22 somaclones (9.1%) differed significantly from the parent and from the other somaclones judged by quantitative protein pattern variations. Three distinctive lineages through tissue culture produced plantlets. Using a discriminant analysis strategy somaclones could be grouped according to lineage with 80.8% accuracy based upon distinctions between protein electrophoretic patterns. Two of the somaclone lineage groupings showed no overlap with the parental grouping which indicated significant molecular divergence of these plantlets as judged by quantitative protein differences.     

Effects of Abscisic Acid and Water Stress on Development and Morphology of Wheat

Experiments were conducted to compare the effects of abscisicacid (ABA) and water stress treatments on leaf morphology andfloral development in a spring wheat. In one experiment injectionsof ABA or a control solution were given twice a week into thebase of the main stem for a period of 3 weeks. In a similarexperiment control plants were watered daily and treated plantswere subjected to water stress by watering only once a week.In both experiments the treated plants produced smaller leavesand fewer spikelets per ear. Analysis of epidermal morphologyusing polystyrene imprints of selected leaf blades from themain stem and a tiller of each plant showed that, compared withcontrol plants, both ABA and water stress decreased the meancell size, reduced the number of stomata per leaf, and increasedthe production of trichomes in all the leaves sampled. Datafor stomatal lengths and stomatal indices showed differencesbetween a main stem leaf and a tiller leaf which were consistentfor both experiments. It is concluded that ABA could mediatemany of the responses of wheat plants to prolonged water stress.The possible adaptive value of these responses is discussed.     

The effect of stem diameter on European corn borer behavior and survival: potential consequences for IRM in Bt-corn

The ability of non-crop plants to support complete development of insect pests is an important factor for determining the impact of those plants on resistance management programs for transgenic crops. We assessed the effect of one physical factor, plant stem diameter, on the ability of plants to support full development of the European corn borer (ECB), Ostrinia nubilalis Hübner (Lepidoptera: Crambidae), the target pest of transgenic Bt-corn. In the field, European corn borer larvae were significantly more likely to tunnel and survive in plants with larger stem diameters. Larvae were 40× more likely to survive on corn, the largest plant tested, compared to many of the smaller plants. In the laboratory, larvae were more likely to survive in and less likely to abandon the largest diet-filled artificial stems that varied only in stem diameter. In conditions simulating those that an ECB larvae would encounter upon abandoning a host, larvae survived up to three weeks and were able to locate corn as a new host with a significantly higher frequency than would be expected if they were foraging randomly. These results indicate that the probability of ECB larval survival to maturity on a plant other than corn is relatively low and thus these smaller stemmed non-corn plants may not make a substantial contribution to the pool of susceptible adults. Conversely, since more mature larvae are not as susceptible as neonates, any larvae that partially develop on non-corn plants and subsequently colonize Bt-corn may not be exposed to a lethal dose of the toxin. Since some proportion of the individuals that survive could be partially resistant heterozygotes the presence of non-corn host plants could facilitate the development of resistant ECB populations.     

The role of organic amendments to soil for crop protection: Induction of suppression of soilborne pathogens

Application of external organic inputs to soils can be considered as one of the most ancient strategies in agriculture, and it has been commonly used since the very beginning of human-based agricultural practices. During all this time, application of several organic matters to agricultural soils has demonstrated their benefit to plants and soils. Organic amendments have proved to be useful in recovering soil properties, improving soil quality and, in some cases, can be directly involved in providing beneficial effects to plants. All these obtained effects finally lead to an increase in crop protection and sustainability. One most expected effect caused by the application of organic amendments, is the suppression of a wide range of soilborne pathogens (mainly bacterial and fungal pathogens) due to the induction of physicochemical and biological changes in soils. In order to get insight into the nature of the induced soil suppression of soilborne plant pathogens, the analysis of the physical, chemical and the microbial changes, pointed to the key role of beneficial activities produced by soil microorganisms finally adapted to the environmental changes produced by the influence of organic amendments. As shown in the case studies reported here, participation of soil microbes specifically selected after organic amendment is crucial in the control of fungal soilborne diseases. Moreover, the development of “omics” approaches allowed these recent studies to go one step further, revealing the main actors involved in the induced soil suppressiveness and their activities. Thus “omics” techniques will help to understand the soil and its microbiome as a whole system, and to assign the important roles of its biological components.     

Plant-derived human recombinant growth factors and serum albumin maintain stemness of human-induced pluripotent stem cells

Stem cells are an important therapeutic source for recovery and regeneration, as their ability of self-renewal and differentiation offers an unlimited supply of highly specialized cells for therapeutic transplantation. Growth factors and serum are essential for maintaining the characteristics of stem cells in culture and for inducing differentiation. Because growth factors are produced mainly in bacterial (Escherichia coli) or animal cells, the use of such growth factors raises safety concerns that need to be resolved for the commercialization of stem cell therapeutics. To overcome this problem, studies on proteins produced in plants have been conducted. Here, we describe the functions of plant-derived fibroblast growth factor 2 (FGF2) and human serum albumin in the maintenance and differentiation of human-induced pluripotent stem cells (hiPSCs). Plant-derived FGF2 and human epidermal growth factor EGF were able to differentiate hiPSCs into neural stem cells (NSCs). These NSCs could differentiate into neuronal and glial cells. Our results imply that culturing stem cells in animal-free culture medium, which is composed of plant-derived proteins, would facilitate stem cell application research, for example, for cell therapy, by reducing contamination risk.     

Canopy development of a determinate and an indeterminate cultivar of Vicia faba L. under contrasting plant distributions and densities

Field experiments were conducted in 1987 and 1988 to quantify differences in canopy formation between an indeterminate and a determinate genotype of Vicia faba L., grown at two plant densities and three spatial distributions. The number of stems per unit area produced by determinate plants was related to the growth rate before flowering. Leaf production per stem per unit of thermal time was similar in both plant types, but twice as many leaves per stem were produced by the indeterminate cultivar. The indeterminate cultivar produced fewer and smaller leaves in the warmer and drier weather of 1988 than in 1987. The determinate genotype produced similar sizes and numbers of leaves in both years, but fewer tillers developed in 1988 than in 1987. Accordingly, leaf mass per unit ground area was greater in 1987 than in 1988 in both genotypes. Except during early flowering, relationships between leaf mass and leaf area were constant, with higher specific leaf areas in the determinate than the indeterminate genotype. Shoot dry matter partitioning into leaves was identical in both years for indeterminate plants, but differed in determinate ones.
It is concluded that canopy development is regulated through individual leaf weight and leaf number per stem in non-tillering indeterminate, and by stem numbers per unit area in tillering determinate plants.     

Root biomechanics and whole-plant allocation patterns: responses of tomato plants to stem flexure

Cherry tomato plants (Lycopersicon esculentum Mill.) were grownwith or without stem flexure similar to that caused by windin order to determine whether stem flexure affects whole-plantbiomass allocation and increases the ability of a plant to withstandwind- induced forces. After 6 weeks of flexing (1 mm, 6 days/week),whole plants were harvested. The main differences found betweentreatments were in the primary shoot/root axis. The stem wassignificantly shorter and wider near the shoot/root junctionin flexed than control plants, both above- and below- ground.Flexed plants had significantly higher root/shoot dry weightratios than controls, but flexed plants and controls did notdiffer significantly in total leaf area, root length, or totalbiomass. Lateral roots from the top 2 cm of the taproot werenot affected by the flexing treatment for any of the factorsstudied: number of laterals, proximal diameter, elastic modulus,stress at failure, or work to failure. Lastly, the force requiredto uproot flexed plants did not differ significantly from thatfor controls. However, because their stems were shorter, flexedplants would have been subjected to smaller stem bending momentsand thus less stress near their root crowns than would controls.Moreover, flexed plants have wider stem bases, and should thusbe better able to resist the forces that affect stems. Thissuggests that in a windy situation, plants that have previouslybeen subjected to flexing could potentially withstand more forcethan unflexed controls. Key words: Anchorage, root, wind, mechanical stimulation, tomato