烟草叶片中草酸形成有其向下运输（简报）

水培条件下烟草根、茎、叶中的草酸含量呈极显著正相关。光照条件下用^14CO2饲喂烟草叶片后,叶中很快有大量^13C-草酸形成,随后分别在茎、根中检测到^14C－草酸,时间上相差约１h。这表明烟草叶片通过光合固定CO2,其光合产物可很快转化为草酸,部分草酸可通过茎向根部运输。     

烟草植株各部位的草酸含量变化（简报）

土培与水培的中烟90烟草植株中草酸含量呈现叶片与根中高,茎中低的哑铃状,根中含量高于叶片,根、,不同叶位叶片和不同部位茎中含量在在早晚没有明显差异。叶片中的含量随叶位不同而不同,成熟叶的含量高于幼叶和老叶。     

植物中草酸积累与光呼吸乙醇酸代谢的关系

对几种C3 和C4 植物中草酸含量及相应的乙醇酸氧化酶活性测定结果表明 :叶片光呼吸强度及其关键酶活性大小与草酸积累量没有相关性 ;植物根中均能积累草酸 ,但未测出乙醇酸氧化酶活性。烟草根、叶中的草酸含量在不同生长时期差异明显 ,且二者呈极显著正相关 (y =2 .5 6 5lnx 2 .137,r =0 .749,P <0 .0 0 1) ,说明根中草酸可能来自叶片。氧化乙醇酸的酶的活性与氧化乙醛酸的酶的活性呈极显著线性正相关 (y =0 .2 41x 0 .0 0 6 ,r=0 .96 7,P <0 .0 0 0 1) ,进一步证实是乙醇酸氧化酶催化了两种底物的反应。烟草在不同生长期叶片中草酸总含量变化与相应的乙醇酸氧化酶活性变化亦没有相关性 ;低磷胁迫可显著诱导烟草根叶中的草酸形成和分泌 ,但并未影响乙醇酸氧化酶活性 ,进一步证明草酸积累与该酶活性大小无关     

大气CO_2浓度和供氮水平对油菜前期生长及氮素吸收利用的影响

采用砂培试验,在2种CO2浓度(自然CO2浓度400μmol·mol-1和高CO2浓度700μmol·mol-1)和2种供氮水平(常氮15 mmol N·L-1和氮胁迫5 mmol N·L-1)下,研究了油菜营养生长阶段的干物质累积和氮素吸收利用的变化。结果表明:高CO2浓度条件下,油菜株高、根茎粗和干物质累积量增加,其中,常氮条件下,根茎粗和地上部干重的增加幅度大于氮胁迫条件,株高和根系干重增加幅度则常氮条件小于氮胁迫条件;高CO2浓度下,根体积、根系活跃吸收面积和总吸收面积在2个供氮水平下均增加,而一级侧根数只在常氮条件下增加,根长只在氮胁迫条件下增加;高CO2浓度条件下,油菜各器官含氮量下降,其中,叶片和根系的含氮素量下降幅度明显大于茎;高CO2浓度条件下,正常供氮时根、茎、叶氮素累积量均增加,氮胁迫时茎氮素累积量增加,而根和叶的氮素累积量减少;高CO2浓度条件下,氮素吸收效率、氮素利用效率和氮效率均增加,常氮条件下增加幅度大于低氮条件,其中,氮素利用效率对氮水平的响应更加明显。     

烟草在PVY~N病毒与烟蚜作用下对高CO_2浓度的响应

以CO2浓度为主处理因子,研究了加倍CO2浓度和对照大气CO2浓度条件下,烟蚜、马铃薯Y病毒N株(PVYN)以及二者共同作用下烟草各指标的响应。结果表明,在当前CO2浓度条件下,PVYN、烟蚜及两者联合作用对烟草生物量影响不显著;而在未来高CO2浓度条件下,PVYN、烟蚜及两者联合作用对烟草生物量影响很大。CO2浓度升高后,PVYN和蚜虫二者联合作用显著降低烟草产量,危害加重,高CO2的"肥料"作用被极大地削弱。在有烟蚜、PVYN以及两者共同作用时烟草的化学物质及主要的次生代谢物烟碱的含量对CO2浓度升高的响应也发生一定的变化,表现在:高CO2浓度条件下,蚜虫、蚜虫与PVYN共同作用显著增加了烟草的含氮量;显著减少了烟叶含糖量;PVYN及其与蚜虫共同作用显著升高叶片可溶性蛋白含量;当高CO2浓度下,各处理的烟草烟碱含量均显著下降,而且PVYN感染的烟叶烟碱含量无论在哪一种CO2浓度条件下,都比无毒无虫的对照烟叶烟碱含量升高。结果显示,烟蚜和马铃薯Y病毒N株(PVYN)对烟草的产量、营养物质及防御物质都有影响;CO2浓度升高对烟草的生长有促进作用,增加了烟草的产量,但蚜虫的危害和PVYN感染使烟草产量下降,在高CO2浓度条件下,烟蚜和PVYN共同作用相对于目前CO2浓度对烟草产量的危害加重。     

杨柴对高CO2浓度和土壤干旱胁迫的响应

毛乌素优势植物杨柴 (HedysarummongolicumTurcz.)对高CO2 浓度和土壤干旱胁迫响应的研究结果表明 :干旱胁迫可使杨柴根系伸长 ,根生物量、地径、主茎高和茎生物量下降 ;高CO2 浓度使杨柴根和茎生物量明显增加 ,CO2 的“施肥效应”显著 ,干旱使CO2 的“施肥效应”减弱。同时 ,土壤干旱胁迫使杨柴的根 /冠比增加 ,说明在土壤干旱胁迫情况下根的生长比地上部分 (茎 )的生长更活跃 ,有利于提高杨柴在干旱沙漠地区的固沙作用 ;CO2 浓度升高和土壤干旱胁迫均使杨柴叶片的水势下降 ,叶片水势的下降使叶片细胞对水分的束缚力增强 ,从而减少植物蒸腾耗水 ,有利于提高水资源的利用效率     

应用~(125)碘、~(14)碳标记化合物研究4-碘苯氧乙酸(增产灵)在水稻上的吸收、运转和积累过程

以~(14)C-氯代乙酸钠制备~(14)C-增产灵;以 Na~(125)I制备~(125)I-增产灵。在孕穗期或湖浆初期,采取叶面涂布、喷施或淋浇根部方法,将标记物分别引进水稻体内。 涂布~(125)I-增产灵(1000 ppm,0.1毫升)于剑叶面3小时后,标记物在叶片中已达附着量的75.2％;一部分标记物并从叶片传递至叶鞘、茎、穗及其它叶片,其中以叶鞘的积累量较多。 叶面喷施~(125)I-增产灵(100 ppm),l小时内渗入量为附着量的26.5％,随时间延长,吸收量增加。标记物在叶片积累量最多,叶鞘次之,运入茎与穗很少,加入0.1％肥皂液可增加叶面药液附着最及渗入量,但不会使叶鞘、茎、穗中的积累量增多。 通过根系吸收的~(125)I-增产灵大部分留在根内,少部分向上运转,以叶鞘积累量较多,茎部次之,叶片及穗部运入量很少。 在水稻生育后期喷施增产灵,糙米中的标记物残留量在2ppm以下。 在显微放射自显影中,~(14)C-增产灵的轨迹首先在茎的维管束及其周围细胞中密集出现,其后分散在茎叶的薄壁组织中。标记物较多地积聚于叶、茎中,推论增产灵有调节韧皮部的运输和动员贮藏物向代谢中心运输的作用。     

光强对烟草幼苗形态和生理指标的影响

通过白纱布遮荫模拟不同光生境条件(透光率分别为100%、68.2%、35.4%和16.7%),研究了光强因子对烟草幼苗形态和生理指标的影响.结果表明:随相对光强的减弱,幼苗高度增加,茎粗、干鲜比、叶片厚度和单位叶面积质量均呈降低趋势,幼苗干物质积累减少,但其对叶数的影响不大.弱光条件下,叶片自由水、叶绿素、总氮和蛋白质含量增加,束缚水含量降低,叶绿素a/b值减小,转化酶活性降低;烟草幼苗根系相对不发达,根冠比和根生物量减小,根系活力降低.表明弱光条件不利于培育烟草壮苗,生产中应尽可能改善苗床的光照条件.     

硅和稻瘟病菌接种对水稻植株有机酸含量的影响

以抗病性不同的一对水稻近等基因系——感病CO39和抗病C101LAC(Pi-1)为实验材料,在水培条件下研究了施硅和稻瘟病接菌对水稻根系和叶片抗性物质有机酸含量的影响,揭示硅提高水稻对稻瘟病抗性的机理。结果表明:接菌条件下硅处理显著降低了2个基因型材料的叶片反丁烯二酸、柠檬酸的含量,而增加了叶片中草酸、顺丁烯二酸的含量;加硅显著降低接菌后第3天的CO39叶片酒石酸含量,但增加了C101LAC(Pi-1)接菌后第7天的叶片酒石酸含量;硅处理还显著增加了根系中苹果酸和草酸的含量;各种有机酸在水稻植株体内的分布也不尽相同,如柠檬酸主要分布在叶片中,苹果酸主要分布在根系中,顺丁烯二酸、反丁烯二酸、酒石酸和草酸在叶片和根系中都有分布。研究表明,硅可能通过影响植株体内的有机酸代谢而增强稻瘟病的抗性。     

烟草根培养的植株再生

菸草是通过组织培养研究形态发生极为良好的试验材料,以往利用烟草的叶片和茎段等培养曾作过不少工作。但利用烟草根段进行培养则未见报道。为了进一步扩大烟草材料的试验范围及探讨烟草根的脱分化能力、要求的条件及植株再生的规律,本试验用烟草根段进行了培养并经愈伤组织或直接分化出芽两种形式获得植株。     

Metabolic fate of 14C-labelled nicotinamide and adenine in germinating propagules of the mangrove Bruguiera gymnorrhiza

We studied the metabolic fate of [carbonyl-14C]nicotinamide and [8-(14)C]adenine in segments taken from young and developing leaves, stem, hypocotyls, and roots of a shoot-root type emerging propagule of the mangrove plant Bruguiera gymnorrhiza. Thin-layer chromatography was used together with a bioimaging analyser system. During 4 h of incubation, incorporation of radioactivity from [carbonyl-14C]nicotinamide into NAD and trigonelline was found in all parts of the propagules; the highest incorporation rates into NAD and trigonelline were found in newly emerged stem and young leaves, respectively. Radioactivity from [8-(14)C]adenine was distributed mainly in the salvage products (adenine nucleotides and RNA), and incorporation was less in catabolites (allantoin, allantoic acid, and CO2). Adenine salvage activity was higher in young leaves and stem than in hypocotyls and roots. Over a short time, the effect of 500 mM NaCl on nicotinamide and adenine metabolism indicated that NaCl inhibits both salvage and degradation activities in roots.     

Translocation of Shoot-Applied Indolylacetic Acid into the Roots of Populus tremula

Application of 10 to 100 μg indol-3-ylacetic acid to the leaves of rooted cuttings of aspen caused inhibition of root growth after three hours. Root growth recovered within 24 hours after IAA treatment. Swelling of the root tips occurred during the period of inhibition. The roots responded in the same way if IAA was applied in solution to the cut stem surface above the mature leaves. IAA-1-¹⁴C applied through a cut stem surface or to mature leaves was translocated downwards in the plants and labelled IAA could be isolated from the roots 3 to 24 hours after application. The ethanol-soluble activity decreased rapidly indicating a rapid metabolism or binding of IAA. IAA-1-¹⁴C applied to growing leaves was not translocated. From the rapid response of root growth it was concluded that IAA was translocated into the roots at a rate of about 7 cm per hour. This rate of translocation indicates that the sieve tubes are involved in the translocation. Implications of the results for the translocation of endogenous auxin into the roots are discussed.     

LEAF DEVELOPMENT,PHOTOSYNTHESIS, AND C14 DISTRIBUTION IN POPULUS DELTOIDES SEEDLINGS

Rates of net photosynthesis and dark respiration and distribution of C¹⁴ from selected leaves were determined for young cottonwood (Populus deltoides) trees at different stages of development. Four series of five trees—one series for each of four treated leaf positions—were included in the study. Maximum C¹⁴ export occurred when a leaf had just attained maximum size. Lower stem leaves reached maturity quickly and began exporting photosynthate when demands of the young seedling were high. Leaves at higher stem positions matured more slowly, but senescence was also delayed so their effective export life was prolonged. Translocation from a newly exporting leaf was primarily upward to developing leaves and the apex. As a leaf at any one position aged, the translocation pattern gradually shifted from upward to bi-directional and finally to a predominantly downward direction. Photosynthate translocated downward was incorporated into stem wood and roots. Maximum photosynthetic efficiency coincided with the downward shift of C¹⁴ export. Thereafter, net photosynthesis began to decline, at first slowly and then more rapidly. The patterns of photosynthesis, respiration, and C¹⁴ export associated with leaf age all varied according to leaf position on the stem.     

The Distribution Pattern of 14Carbon Assimilated by the Third Leaf of Wheat

The third leaf of wheat, variety Jufy I, was allowed to assimilate¹⁴CO₂ for 2 hrs.; after a further hour the distribution patternof the assimilates was determined. Uptake of ¹⁴CO₂ and assimilatesleaving the leaf increased until the leaf was fully expanded,then slowly decreased. High proportions of labelled translocates were recorded in boththe stem and the the root system, that in the roots increasinggreatly as movement of translocates to the leaves decreased.The two fully grown leaves, L₁ and L₂, imported only slightamounts of labelled translocates. Movement of labelled translocateto each of the younger leaves in turn occurred in a strikingpattern, such that import into a given leaf reached a maximumwhich coincided with its maximum rate of growth, subsequentlyfalling rapidly and reaching a very low level by the time theleaf is fully grown. The results are discussed in relation to what is known of thegeneral pattern of growth and translocation in the wheat plant.     

An analysis of responses of resistant and of susceptible tomato plants to Verticillium infection

Comparative studies were made of the responses of resistant and of susceptible Gem tomato plants to infection by Verticillium albo-atrum. When inoculated through roots, there were striking differences in their responses. In susceptible plants, the foliar symptoms and amount of mycelium in the stem increased rapidly for some time. Then the mycelium started to disappear from the stem; this was accompanied by a check to the normal progress of symptoms, and by the formation of tyloses. In resistant plants, a limited invasion of the root and lower stem was accompanied by rapid and extensive tylosis. The mycelium soon disappeared from the stem and the plant then recovered from the initially mild symptoms. There was an inverse relationship between the amount of mycelium and the extent of tylosis in infected plants. The growth of susceptible plants was markedly reduced by infection. Total leaf area was much less because the newly produced leaves did not expand normally. The root system in infected plants was smaller because there were many fewer tertiary roots. In resistant plants infection stimulated growth. Tomato cuttings inoculated with conidia reacted similarly to root-inoculated plants. Hyphae grew well in the vascular system of susceptible cuttings whereas in resistant cuttings the pathogen started to grow but soon disappeared. Detached leaves of susceptible plants, inoculated through cut ends, wilted more than did leaves from resistant plants. It is suggested that resistance is mainly of the active type that develops after infection.     

Identification of phosphoenolpyruvate carboxylase isoforms in leaf, stem and roots of the obligate CAM plant Vanilla planifolia Salib. (Orchidaceae): a physiological and molecular approach

This study provides the first comparative analysis of phosphoenolpyruvate carboxylase isoforms (PEPc; EC 4.1.1.31) in an obligate crassulacean acid metabolism (CAM) plant, Vanilla planifolia Salisb. (Orchidaceae). Nocturnal CO2 fixation and malate accumulation by the leaves and the green stem show that these organs perform CAM. The chloroplast-containing aerial roots, however, exhibit C3 photosynthesis. The catalytic activity of PEPc was highest in the leaves compared with the stem and aerial roots. The Km (PEP) and Ki (malate) were similar in the PEPc extracted from leaf and aerial roots, and significant higher in stem. cDNA was obtained from those tissues and also from the soil-grown roots, and various cDNA clones were detected and amplified by means of RT-PCR and RACE-PCR. The amino-acid sequences of the PEPc isoforms deduced from the cDNA showed a great degree of homology, and Southern blot analysis suggests that the encoding genes form a small multigene family of at least two members. One PEPc isoform (PpcV1) is assumed to be related to CAM because, as shown by northern blot analysis, it is mainly expressed in the CAM-performing organs, i.e. in the leaves and the stem. A further isoform (PpcV2) was identified in the soil-grown roots and aerial roots, but northern blots show that to some extent PpcV2 is also expressed in the leaf and the stem tissues. Thus, it is assumed that PpcV2 encodes the housekeeping isoform of PEPc. Altogether, the present study provides support in favour of the view that isoforms of PEPc are related to specific functions.     

Uptake and Translocation of Benthiocarb Herbicide by Plants

The uptake and translocation of ¹⁴C-benthiocarb labelled at benzyl methylene by rice plant, bamyardgrass, wild amaranth, smart weed and lambsquarters were investigated, ¹⁴C-Benthiocarb was absorbed through the roots and the radioactivity was translocated into whole plants. The rate of absorption and translocation varied by the kind of plants. The translocation was occurred not only from roots into leaves, but from a leaf into other leaves, and even into roots of some kinds of plant. The absorption and translocation was more easy in barnyard-grass than in rice plant. Benthiocarb was rapidly absorbed by seeds and accumulated mostly in the embryo. The uptake of benthiocarb by seedlings decreased with the order of mesocotyl (bamyardgrass only), coleoptyl, root and leaf. Benthiocarb was degraded rapidly in plants.     

Aquatic adventitious roots of the wetland plant Meionectes brownii can photosynthesize: implications for root function during flooding

? Many wetland plants produce aquatic adventitious roots from submerged stems. Aquatic roots can form chloroplasts, potentially producing endogenous carbon and oxygen. Here, aquatic root photosynthesis was evaluated in the wetland plant Meionectes brownii, which grows extensive stem-borne aquatic roots during submergence. ? Underwater photosynthetic light and CO(2) response curves were determined for aquatic-adapted leaves, stems and aquatic roots of M. brownii. Oxygen microelectrode and (14)CO(2)-uptake experiments determined shoot inputs of O(2) and photosynthate into aquatic roots. ? Aquatic adventitious roots contain a complete photosynthetic pathway. Underwater photosynthetic rates are similar to those of stems, with a maximum net photosynthetic rate (P(max)) of 0.38 μmol O(2) m(-2) s(-1); however, this is c. 30-fold lower than that of aquatic-adapted leaves. Under saturating light with 300 mmol m(-3) dissolved CO(2), aquatic roots fix carbon at 0.016 μmol CO(2) g(-1) DM s(-1). Illuminated aquatic roots do not rely on exogenous inputs of O(2). ? The photosynthetic ability of aquatic roots presumably offers an advantage to submerged M. brownii as aquatic roots, unlike sediment roots, need little O(2) and carbohydrate inputs from the shoot when illuminated.     

Distribution of assimilate during the flush cycle of growth in Theobroma cacao L.

The growth of the shoot and roots of seedling plants of cocoa (Theobroma cacao L.) under constant glasshouse conditions showed a rhythmic cycle, with the maximum growth stages of each alternating in a regular sequence. When the growth cycle of the shoot was upset by removing all new leaves immediately after unfolding, the roots showed a high constant growth rate during this period, suggesting that normally the rapidly expanding leaves exert an inhibitory influence on the roots. Conversely removal of portions of the root delayed the production of new leaves in the shoot. The level of soluble and starch carbohydrate in the mature leaves, roots and stem declined during the period of expansion of the flush leaves, but accumulated again at the end of the leaf expansion stage. It is likely that this reserve carbohydrate was remobilised and translocated to the flush leaves during their period of expansion. A large proportion of newly formed photoassimilate, as shown by the distribution of ¹⁴C radioactivity from different source leaves, was also translocated to the young leaves during expansion. The large sink created by these leaves may cause photoassimilate and reserve carbohydrate to be diverted from the roots, thereby inhibiting root growth during the stage of leaf expansion. It is suggested that the rhythmic leaf production at the apex may control the growth cycle of the roots.