Development,differentiation,and material distribution of secondary phloem in Pinus massoniana

Phloem is the woody tissue for the storage and long-distance transport of organic matter in vascular bundles.To reveal the process of secondary phloem development and differentiation in Pinus massoniana,the structure of the secondary phloem and the distribution of cell inclusions were observed by histochemical staining,spontaneous fluorescence of phenolic substances and cell segregation.Based on tissue development and differentiation characteristics of P.massoniana secondary phloem,the secondary phloem development was divided into seven stages:the functional phloem stage;the sieve cell lignification stage;the phloem ray bending stage;the parenchyma cell dedifferentiation and division stage;the dedifferentiated parenchyma cell population formation stage;the periderm alteration stage,and the rhytidome stage.An analysis of cell morphology and inclusion distribution characteristics showed that the sieve cells were deformed during lignification,the quantities of parenchyma and resin ducts increased with development and the crystal content in cells,as well as the levels of sugars and lipids in phloem parenchyma cells,increased with development.The results indicate that the P.massoniana phloem first lost longitudinal transport function and then increased its secretory,storage and mechanical functions.Ultimately,the parenchyma differentiated into the cortex and periderm,and the tissue outside the new periderm lignified to form the rhytidome,which fully developed into the protective tissue of the stem.

Evidence of the predominance of passive symplastic phloem loading and sugar transport with leaf ageing in Camellia oleifera

Phloem loading and transport of sugar from leaves to sink tissues such as fruits are crucial for yield formation.Camellia oleifera is an evergreen horticultural crop with high value;however,its low production limits the development of the C.oleifera industry.In this study,using a combination of ultrastructural observation,fluorescence loss in photobleaching(FLIP)and inhibitor treatment,we revealed that C.oleifera leaves mainly adopt a symplastic loading route from mesophyll cells to the surrounding vascular bundle cells in minor veins.HPLC assays showed that sucrose is the main sugar transported and only a small amount of raffinose or stachyose was detected in petioles,supporting a passive symplastic loading route in C.oleifera leaves.Compared to leaves grown this year(LT),the carbohydrate synthesis capacity in leaves grown last year(LL)was decreased while LL retained more soluble sugar,suggesting a decrease in transport capacity with leaf ageing.TEM and tissue staining showed that a reduction in plasmodesmata density leads to a decline in the degree of cellular coupling and is responsible for the weakening transport capacity in older leaves.RNA-seq revealed several differentially expressed genes(DEGs)including CoPDCB1-1,CoSUT1 and CoSWEET12,which are likely involved in the regulation of phloem loading and sugar transport.An expression correlation network is constructed between PD-callose binding protein genes,sugar transporter genes and senescence-associated genes.Collectively,this study provides the evidence of the passive symplastic phloem loading pathway in C.oleifera leaves and constructs the correlation between sugar transport and leaf ageing.

Anatomical and FTIR analyses of phloem and xylem of Tetracentron sinense

The fast growth of Tetracentron sinense is a potential valuable timber resource, but whether its anatomy and chemical components are suitable for timber is unknown. We used light microscopy and SEM to examine the anatomical structure and FITR to measure the chemical components of the phloem and xylem of this tree. Radial variations in growth ring width and tracheid dimensions were also evaluated. The sieve tube, phloem parenchyma cell and sclereids clusters were the main cells in phloem, and the tracheid was the fundamental cell in xylem. An unusual tracheid type, fiber-tracheids or vessel-liked elements was visible. Wood rays nonstoried, uniseriate and multiseriate, including heterogeneous II, occasionally I, and usually 3-6 cells wide. The mean growth-ring width was 2.53 +/- 0.46 mm, and the percentage of late wood was over 60%. For radial variation, growth-ring width increased at an early growth stage, and reached the largest increment during years 11-15, then decreased. The maximum growth-ring width was 5.313 mm. During late growth (60-85 years), trees also maintained a high radial growth increment. Radial variation in the percentage of late wood was uniform, about 50-70%, throughout the growth years. Growth patterns in the length and width of early and late wood were similar as the trees aged. From the FTIR results, the chemical components differed significantly between xylem and phloem, hemicellulose in particular was higher in the xylem than in the phloem, where it was apparently absent. All of these suggest that the composition of phloem in T. sinense is very similar to that of hardwood, and it has higher growth ratio and uniform wood properties.

Overexpression of rice F-box phloem protein gene OsPP12-A13 confers salinity tolerance in Arabidopsis

Salinity is a serious challenge for agriculture production by limiting the arable land.Rice is a major staple food crop but very sensitive to salt stress.In this study,we used Arabidopsis for the functional characterization of a rice F-box gene LOC_Os04g48270(OsPP12-A13)under salinity stress.OsPP12-A13 is a nuclear-localized protein that is strongly upregulated under salinity stress in rice and showed the highest expression in the stem,followed by roots and leaves.Two types of transgenic lines for OsPP12-A13 were generated,including constitutive tissue over-expression using the CaMV35S promoter and phloem specific over-expression using the pSUC2 promoter.Both types of transgenic plants showed salinity tolerance at the seedling stage through higher germination percentage and longer root length,as compared to control plants under salt stress in MS medium.Both the transgenic plants also exhibited salt tolerance at the reproductive stage through higher survival rate,plant dry biomass,and seed yield per plant as compared to control plants.Determination of Na+concentration in leaves,stem and roots of salt-stressed transgenic plants showed that Na^(+) concentration was less in leaf and stem as compared to roots.The opposite was observed in wild type stressed plants,suggesting that OsPP12-A13 may be involved in Na+transport from root to leaf.Transgenic plants also displayed less ROS levels and higher activities of peroxidase and glutathione S-transferase along with upregulation of their corresponding genes as compared to control plants which further indicated a role of OsPP12-A13 in maintaining ROS homeostasis under salt stress.Further,the non-significant difference between the transgenic lines obtained from the two vectors highlighted that OsPP12-A13 principally works in the phloem.Taken together,this study showed that OsPP12-A13 improves salt tolerance in rice,possibly by affecting Na^(+) transport and ROS homeostasis.

Free amino acid (FAA) analysis of phloem sap in hybrid rice Shanyou 63 and its parents

Hyhrid rice has greatly contributed to rice production inChina. But concurrently a dramatic upsurge of rice plant-hopper occurred, particularly for the whitebacked plant-hopper (WBPH), Sogatella furcifera. It has become animportant economic insect pest of hybrid rice, although ithad only been a minor herbivore of rice before nation-wideexploitation of hybrid rice.

园艺植物韧皮部卸载研究进展

植物韧皮部卸载包括一系列复杂的过程,韧皮部卸载在园艺植物(果树、蔬菜、观赏植物)同化物的运输和分配中具有重要作用。本研究概述了韧皮部卸载的主要途径,并重点综述了韧皮部卸载在园艺植物生长发育方面的主要研究成果,内容包括:①韧皮部运输的主要糖分物质;②韧皮部卸载方式;③韧皮部卸载研究方法;④园艺植物韧皮部卸载研究。随着研究的深入和新技术的出现,园艺植物韧皮部卸载过程中涉及的关键酶与蔗糖转运蛋白等需得到更深入地阐释,进一步助力解析植物韧皮部卸载参与园艺植物生长发育的分子调控机制,并有望为更多的植物韧皮部卸载研究提供新的思路。

Ultrastructure of compatible and incompatible interactions in phloem sieve elements during the stylet penetration by cotton aphids in melon

Resistance of the melon line TGR-1551 to the aphid Aphis gossypii is based on preventing aphids from ingesting phloem sap. In electrical penetration graphs （EPGs）, this resistance has been characterized with A. gossypii showing unusually long phloem salivation periods （waveform El） mostly followed by pathway activities （waveform C） or if followed by phloem ingestion （waveform E2）, ingestion was not sustained for more than 10 min. Stylectomy with aphids on susceptible and resistant plants was performed during EPG recording while the stylet tips were phloem inserted. This was followed by dissection of the penetrated leaf section, plant tissue fixation, resin embedding, and ultrathin sectioning for transmission electron microscopic observation in order to study the resistance mechanism in the TGR. The most obvious aspect appeared to be the coagulation of phloem proteins inside the stylet canals and the punctured sieve elements. Stylets of 5 aphids per genotype were amputated during sieve element （SE） salivation （El） and SE ingestion （E2）. Cross-sections of stylet bundles in susceptible melon plants showed that the contents of the stylet canals were totally clear and also, no coagulated phloem proteins occurred in their punctured sieve elements. In contrast, electron-dense coagulations were found in both locations in the resistant plants. Due to calcium binding, aphid saliva has been hypothesized to play an essential role in preventing/suppressing such coagulations that cause occlusion of sieves plate and in the food canal of the aphid＇s stylets. Doubts about this role of E 1 salivation are discussed on the basis of our results.

Recycling of Solanum Sucrose Transporters Expressed in Yeast, Tobacco, and in Mature Phloem Sieve Elements

The plant sucrose transporter SUT1 （from Solanum tuberosum, S. lycopersicum, or Zea mays） exhibits redoxdependent dimerization and targeting if heterologously expressed in S. cerevisiae （Krtigel et al., 2008）. It was also shown that SUT1 is present in motile vesicles when expressed in tobacco cells and that its targeting to the plasma membrane is reversible. StSUT1 is internalized in the presence of brefeldin A （BFA） in yeast, plant cells, and in mature sieve elements as confirmed by immunolocalization. These results were confirmed here and the dynamics of intracellular SUT1 localization were further elucidated. Inhibitor studies revealed that vesicle movement of SUT1 is actin-dependent. BFA-mediated effects might indicate that anterograde vesicle movement is possible even in mature sieve elements, and could involve components of the cytoskeleton that were previously thought to be absent in SEs. Our results are in contradiction to this old dogma of plant physiology and the potential of mature sieve elements should therefore be re-evaluated. In addition, SUT1 internalization was found to be dependent on the plasma membrane lipid composition. SUT1 belongs to the detergent-resistant membrane （DRM） fraction in planta and is targeted to membrane raft-like microdomains when expressed in yeast （Kr（igel et al,, 2008）, Here, SUT1-GFP expression in different yeast mutants, which were unable to perform en- docytosis and/or raft formation, revealed a strong link between SUT1 raft localization, the sterol composition and mem- brane potential of the yeast plasma membrane, and the capacity of the SUT1 protein to be internalized by endocytosis. The results provide new insight into the regulation of sucrose transport and the mechanism of endocytosis in plant cells.

Phloem-Mobile AuxlIAA Transcripts Target to the Root Tip and Modify Root Architecture

In plants, the phloem is the component of the vascular system that delivers nutrients and transmits signals from mature leaves to developing sink tissues. Recent studies have identified proteins, mRNA, and small RNA within the phloem sap of several plant species. It is now of considerable interest to elucidate the biological functions of these potential long-distance signal agents, to further our understanding of how plants coordinate their developmental programs at the whole-plant level. In this study, we developed a strategy for the functional analysis of phloem-mobile mRNA by focusing on IAA transcripts, whose mobility has previously been reported in melon （Cucumis melo cv. Hale＇s Best Jumbo）. Indoleacetic acid （IAA） proteins are key transcriptional regulators of auxin signaling, and are involved in a broad range of developmental processes including root development. We used a combination of vasculature-enriched sampling and hetero-grafting techniques to identify IAA18 and IAA28 as phloemmobile transcripts in the model plant Arabidopsis thaliana. Micro-grafting experiments were used to confirm that these IAA transcripts, which are generated in vascular tissues of mature leaves, are then transported into the root system where they negatively regulate lateral root formation. Based on these findings, we present a model in which auxin distribution, in combination with phloem-mobile Aux/IAA transcripts, can determine the sites of auxin action.

Effects of Acetylcholine, Cytochalasin B and Amiprophosmethyl on Phloem Transport in Radish （Raphanus sativas）

We investigated the role of the ＂sieve tube-companion cell complex＂ lining the tube periphery, particularly the microfilament and microtubule, in assisting the pushing of phloem sap flow. We made a simple phloem transport system with a living radish plant, in which the conducting channel was exposed for local treatment with chemicals that are effective in modulating protoplasmic movement （acetylcholine, （ACh） a neurotransmitter in animals and insects; cytochalasin B, （CB） a specific inhibitor of many cellular responses that are mediated by microfilament systems and amiprophos-methyl, （APM） a specific inhibitor of many cellular responses that are mediated by microtubule systems）. Their effects on phloem transport were estimated by two experimental devices： （i） a comparison of changes in the amount of assimilates in terms of carbohydrates and ^14C-labeled photosynthetic production that is left in the leaf blade of treated plants; and （ii） distribution patterns of ^14C-labeled leaf assimilates in the phloem transport system. The results indicate that CB and APM markedly inhibited the transfer of photosynthetic product from leaf to root via the leaf vein, while ACh enhanced the transfer of photosynthetic product in low concentrations （5.0×10^-4 mol/L） but inhibited it in higher concentrations （2.0×10^-3 mol/L） from leaf to root via the leaf vein. Autoradiograph imaging clearly reveals that ACh treatment is more effective than the control, and both CB and APM treatments effectively inhibit the passage of radioactive assimilates. All of the results support the postulation that the peripheral protoplasm in the sieve tube serves not only as a passive semi-permeable membrane, but is also directly involved in phloem transport.

Plant lncRNAs are enriched in and move systemically through the phloem in response to phosphate deficiency

In response to phosphate(Pi) deficiency, it has been shown that micro-RNAs(miRNAs) and mRNAs are transported through the phloem for delivery to sink tissues. Growing evidence also indicates that long noncoding RNAs(lncRNAs) are critical regulators of Pi homeostasis in plants. However, whether lncRNAs are present in and move through the phloem, in response to Pi deficiency, remains to be established. Here, using cucumber as a model plant, we show that lncRNAs are enriched in the phloem translocation stream and respond,systemically, to an imposed Pi-stress. A well-known lncRNA, IPS1, the target mimic(TM) of miRNA399,accumulates to a high level in the phloem, but is not responsive to early Pi deficiency. An additional 24 miRNA TMs were also detected in the phloem translocation stream; among them miRNA171 TMs and miR166 TMs were induced in response to an imposed Pi stress.Grafting studies identified 22 lncRNAs which move systemically into developing leaves and root tips. A CU-rich PTB motif was further identified in these mobile lncRNAs. Our findings revealed that lncRNAs respond to Pi deficiency, non-cell-autonomously, and may act as systemic signaling agents to coordinate early Pi deficiency signaling, at the whole-plant level.

Ultracytochemical localization of Ca^(2+) during the phloem ganglion development in Phyllostachys edulis

Ultracytochemical localization of Ca^(2+)was in-vestigated using the potassium pyroantimonate precipitation method during the development of phloem ganglion.The result showed that Ca^(2+)was mainly localized in the cell wall and intercellular spaces in the initiating phase.With the de-velopment of the phloem ganglion,the distribution of Ca^(2+)transferred to the vacuole,and the Ca^(2+)deposits in the cell wall and intercellular space decreased.At the later stage of the developmental phase,Ca^(2+)was distributed in the tono-plast and vacuole phagocytosis,and the vacuole became the main calcium storage in this phase.At the early stage of maturation of the phloem ganglion,most of the phloem ganglion cells’vacuoles cracked,and the cytoplastic Ca^(2+)content increased in large number.In the mature phloem ganglion,not only were there a few Ca^(2+)localized in the cytoplast of mature cells,but also in the differentiating cells in the vacuoles.Ca^(2+)was distributed in the tonoplast and vacuole contents;initiating cells almost had no Ca^(2+).In general,Ca^(2+)concentration in mature phloem ganglion cells was at a low level.The results indicated that the changes in Ca^(2+)distribution evoked the phloem ganglion generation,and Ca^(2+)regulated the physiological function of the phloem ganglion.

棉秆韧皮浆粕的制备与性能测试

通过高温蒸煮和有机酸与乙醇组合溶解方式对棉秆韧皮进行制浆,并以浆粕得率为依据进行工艺优化。用核磁共振、红外光谱和热重分析等技术对制浆前棉秆韧皮和制浆所得浆粕的聚合度、相对分子量、Iα纤维素含量、分子结构和热学性能等指标进行表征。结果表明:棉秆韧皮制浆的最佳工艺为温度100℃、处理时间120 min、过氧化氢质量分数10%、乙醇质量分数60%;经制浆处理,棉秆韧皮中的木质素和半纤维素发生了部分酯化和酰化,使得其中的Iβ纤维素和微纤维结构受到破坏,热学性能下降,Iα纤维素含量增加。

GTR-Mediated Radial Import Directs Accumulation of Defensive Glucosinolates to Sulfur-Rich Cells in the Phloem Cap of Arabidopsis Inflorescence Stem

In the phloem cap region o i Arabidopsis plants,sulfur-rich cells(S-cells)accumulate>100 mM glucosinolates(GLS),but are biosynthetically inactive.The source and route of S-cell-bound GLS remain elusive.In this study,using single-cell sampling and scanning electron microscopy with energy-dispersive X-ray analysis we show that two GLS importers,NPF2.10/GTR1 and NPF2.11/GTR2,are critical for GLS accumulation in S-cells,although they are not localized in the S-cells.Comparison of GLS levels in S-cells in multiple combinations of homo-and heterografts o lg t r l gtr2,biosynthetic null mutant and wild-type plants indicate that S-cells accumulate GLS via symplasmic connections either directly from neighboring biosynthetic cells or indirectly to non-neighboring cells expressing GTR1/2.Distinct sources and transport routes exist for different types of GLS,and vary depending on the position of S-cells in the inflorescence stem.Based on these findings,we propose a model illustrating the GLS transport routes either directly from biosynthetic cells or via GTR-mediated import from apoplastic space radially into a symplasmic domain,wherein the S-cells are the ultimate sink.Similarly,we observed accumulation of the cyanogenic glucoside defensive compounds in high-turgor cells in the phloem cap of Lotus japonicus,suggesting that storage of defensive compounds in high-turgor cells may be a general mechanism for chemical protection of the phloem cap.

植物中金属纳米粒子的转运与转化机制研究进展

金属纳米粒子(MNPs)的广泛使用对生态环境造成了较大的风险并引起了广泛的关注;虽然已有关于对植物毒害以及植物对其吸收的相关研究,但是MNPs在植物体内转运和转化的机制仍未得到系统的阐明。系统地阐述了MNPs在高等植物木质部、韧皮部中的转运机制,以及其在植物体内的溶解转化和化学转化机制,同时探讨了影响MNPs在植物体内转运转化的影响因素。结果表明:(1)MNPs首先吸附在植物的根部或叶部,再通过质外体或共质体途经向植物内部转移;(2)植物对MNPs的转化机制主要包括溶解转化、化学转化和生物转化(酶降解、蛋白质功能化等);(3)复杂的理化和生物因素(如粒子的种类大小、表面电荷、植物种类等)能够影响植物对MNPs转运及其形态转化。以期为金属纳米粒子污染土壤的生态环境治理和人类健康风险评估提供参考依据。

Inhibition of α-glucosidase activity by N-deoxynojirimycin analogs in several insect phloem sap feeders

Secondary metabolites and synthetic iminosugars that structurally resemble monosaccharides are potent inhibitors of a-glucosidase activity. The enzyme is core in cleaving sucrose in phloem feeding insects and it also plays a crucial role of reducing osmotic stress via the formation of oligosaccharides. Inhibition of hydrolysis by iminosug- ars should result in nutritional deficiencies and/or disruption of normal osmoregulation. Deoxynojirimycin （DNJ） and 2 N-alkylated analogs [N-butyl DNJ （NB-DNJ） and N-nonyl DNJ （NN-DNJ）] were the major iminosugars used throughout the study. The extensive experiments conducted with a-glucosidase of the whitefly Bemisia tabaci indicated the competitive nature of inhibition and that the hydrophilic DNJ is a potent inhibitor in com- parison to the more hydrophobic NB-DNJ and NN-DNJ compounds. The same inhibitory pattern was observed with the psyllid Cacopsylla bidens a-glucosidase. In contrast to the above pattern, enzymes of the aphids, Myzus persicae and Aphis gossypii were more sen- sitive to the hydrophobic iminosugars as compared to DNJ. In vivo experiments in which adult B. tabaci were fed dietary iminosugars, show that the hydrophilic DNJ was far less toxic than the lipophilic NB-DNJ and NN-DNJ. It is proposed that this pattern is attributed to the better accessibility of the hydrophobic NN-DNJ to the a-glucosidase membrane- bound compartment in the midgut. Based on the inhibitory effects of certain polyhydroxy N-alkylated iminosugars, a-glucosidase of phloem feeding hemipterans could serve as an attractive target site for developing novel pest control agents.

The effects of microfilament and microtubule inhibitors and periodic electrical impulses on phloem transport in pea seedling

In phloem transport, whether protoplasmic activity participates in assisting sap flow in sieve element_companion cell complex has long been in debate. The present investigation assumed microfilament (MF) and microtubule (MT), the two constituents of the protoplasmic cytoskeleton, as motive force, and employed germinating pea seedling suspended in moist chamber as experimental material: the seed being the source; the elongating root, the sink. 14 C_labeled sucrose was added to the seed as indicator. The amount of sap transported from source to sink was measured by the increase in root elongation. The transport phloem was within the cylinder of the peeled root in the middle. The exposed cylinder was treated with MF inhibitor (cytochalasin B), or microtubule inhibitor (amiphos_methyl). Results showed that the sap influx into the elongating root, and the 14 C activity as well, was reduced by about one half in treatment with cytochalasin B, and much less by amiphos_methyl treatment. Similar effect was shown in electrical impulse treatment, which seems to disrupt the MF and MT configuration.

基于韧皮部纤维形态、树皮抗拉伸性能的橡胶树耐寒性研究

为探索不同品种橡胶树幼龄树耐寒性与成龄树枝条韧皮部纤维形态、树皮抗拉伸性能之间的关系,分析不同品种橡胶树耐寒性与其相应生理、生物力学指标的相关性,从而比较不同品种橡胶树耐寒性的差异,以期建立不同品种橡胶树幼龄树茎段与成龄树枝条树皮相应指标之间的联系,并从细胞结构及树皮生物力学角度研究橡胶树耐寒性机理。以热研7-33-97、PB86、IAN873、大丰95、云研77-2等5个橡胶树品种1年生芽接苗茎段及相应品种成龄树2年生枝条树皮为材料,测定低温梯度下茎段韧皮部电导率及枝条韧皮部纤维形态、树皮抗拉伸性能指标,利用Logistic方程确定其低温半致死温度(L_(T50))的大小,得出不同品种耐寒性,并采用Spearman相关性分析法,得出L_(T50)与韧皮部纤维形态指标、树皮抗拉伸性能之间的相关性。结果表明,5个橡胶树品种韧皮部相对电导率呈“S”形曲线变化,相对电导率与胁迫温度之间呈极显著负相关,5个品种L_(T50)分别为-2.075℃、-2.240℃、-1.923℃、-1.900℃、-2.186℃;5个品种纤维长度在2921.013~4799.438μm,宽度在21.717~23.908μm,双壁厚度分别为11.504、10.271、10.873、12.715、10.401μm,腔直径分别为0.900、1.423、0.922、1.298、0.915μm,PB86的纤维双壁厚最小,腔直径最大;5个品种树皮厚度分别为0.709、0.564、0.886、0.935、0.774 mm,PB86的树皮厚度与其他品种的差异达到了显著水平(P<0.05),5个品种拉伸破坏荷载在4.935~11.064 N,PB86的抗拉伸强度与最大拉伸位移均为5个品种最大,分别为3.629 MPa、1.360 mm;1年生茎段韧皮部L_(T50)与成龄树2年生枝条韧皮部纤维双壁厚呈显著性正相关,与2年生树皮厚度、抗拉强度分别呈显著性正相关和显著性负相关。从细胞尺度与组织生物力学角度研究橡胶树耐寒性,以此搭建橡胶树幼龄树与成龄树联系的纽带,是橡胶树耐寒机理研究的有效途径。

蕾铃脱落对棉花果枝叶光合产物积累及“源”潜力的影响

【目的】棉花蕾铃脱落率常超过60%,蕾铃脱落后的果枝叶常作为“辅助源”对其邻位铃的发育起重要作用。探明棉花果枝叶在其对位蕾铃脱落后作为“辅助源”的潜力及其变化趋势,丰富棉花产量形成的“源-库”调控理论,为棉花补偿性生长的栽培管理提供理论依据。【方法】以中棉425为材料于2021年分2个播期(5月10日、6月1日)在江苏南京(118°50′E,32°02′N)南京农业大学牌楼试验站开展田间试验,研究果枝韧皮部阻断条件下,去库(化学法阻断第四、五、六果枝第一果节“蕾-对位叶”系统与主茎连接的韧皮部,同时去除该系统蕾/花,模拟蕾铃脱落条件)后棉花果枝叶形态特征、气体交换参数、碳氮物质及内源激素含量等叶片源能力相关指标的变化。【结果】(1)去库处理显著增加了果枝叶中果糖、蔗糖、淀粉、纤维素含量,却显著降低了其葡萄糖含量。随着时间的推延,去库后1 d,淀粉的增幅最大,纤维素增幅则主要在去库后3 d明显变大;去库后5 d,蔗糖、纤维素、淀粉的增幅较大。(2)去库后,糖分更多地以非还原性糖形式积累;光合产物更多地向淀粉形式分配;多聚糖/低聚糖呈先降低后升高的趋势,而果枝叶C/N则呈现先升高后下降的趋势。(3)去库处理显著降低了果枝叶净光合速率和叶绿素含量。(4)果枝叶局部呈现紫红色且花青素含量较对照升高了约2倍。(5)去库后,果枝叶中ABA含量呈上升趋势且显著高于对照,IAA含量呈先上升后下降的趋势;GA3含量在去库处理后显著低于对照,而JA与SA含量则显著高于对照。(6)果枝叶内源激素动态平衡在去库后改变,ABA/IAA、JA/IAA呈现先减小后增大的趋势,而ABA/GA3、JA/GA3则不断增大。【结论】蕾铃脱落后,果枝叶中糖分积累和分配形式及内源激素信号发生显著改变,并对其叶源能力产生显著影响。短期内(1—3 d),果枝叶中糖类物质整体含量增加,尤其是非还原性糖累积幅度较大,源能力快速增强;但随着时间推移,源能力增强幅度下降,同时叶片有早衰趋势,叶绿素降解加速。即蕾铃脱落后,脱落蕾铃的果枝叶对其邻位铃的“辅助源”功能短期内(3 d左右)快速上升,之后快速下降,后期其对邻位铃发育的贡献很小。

β-氨基丁酸-大黄酸耦合物的合成、生物活性及韧皮部传导性

氨基酸-农药耦合物能够改善母体农药的内吸传导性,提高农药的使用效率,减少因没有到达靶标造成的浪费及对环境的污染。本研究以天然产物大黄酸为先导化合物、以β-氨基丁酸为导向基团,设计、合成了4个目标化合物,并检测了其对6种植物病原菌的抑菌活性,以及对小麦植株苯丙氨酸解氨酶(PAL)和过氧化物酶(POD)活性的影响及在蓖麻幼苗中的韧皮部传导性。结果表明,化合物4b(浓度0.5 mmol/L)不仅对水稻纹枯病菌Rhizoctonia solani Kühn具有一定的抑制活性(菌丝生长抑制率为53.5%),而且具有诱导抗性(持效期近7 d)和韧皮部传导性(渗出液浓度为15.1μmol/L)。该研究为兼具内吸传导性和诱导抗性杀菌剂的开发提供了新思路。