Dimethylmorpholinium Chloride Analogs and Their Effect on Plants

Relations between the chemical structure of new analogs of dimethylmorpholinium chloride (DMC) and their growth retardant activity were investigated. Some of these substances exerted a specific impact on the growth of individual organs in monocot (Triticum aestivum L., Hordeum vulgare ssp. distichon (L.) Koern.) and dicot (Phaseolus vulgaris L., Brassica napus L.) plants. Within the group of bis-quaternary ammonium salts, the derivatives of N-methylmorpholinium (1-DMC) and N-benzylmorpholinium (3-DMC) manifested high retardant activity on growth of barley and wheat plants. The molecules of these compounds comprise the chain of two methylene groups bridging the nitrogen atoms. An N-acetylmorpholinium derivative 17-DMC, with nitrogen atoms in morpholinium rings linked by two methylene groups with a CHOH group between them, produced a physiological effect on rape and kidney bean plants.     

Evidence suggests plagiotropic clonal species have evolved a branching physiology emphasizing regulation by nodal roots

In the plagiotropic nodally rooting clonal herb, Trifolium repens,the development of branches on stems is primarily controlled by the presence of nodal roots, and apical dominance is of secondary importance; only six to ten branches form distal to the youngest nodal root on a horizontal stem. We assessed the hypothesis that this phenomenon is general for clonal herbs with prostrate nodally rooting stems, and that they all have the same physiological system regulating branching, by testing a selection of species from diverse angiosperm families that exhibit either phalanx (Leptinella (Asteraceae), Hydrocotyle (Apiaceae), Acaena (Rosaceae)) or guerilla (Vinca (Apocynaceae), Glechoma and Lamiastrum (Lamiaceae)) growth strategies. In all these species the establishment of a single nodal root on a prostrate stem, otherwise prevented from nodally rooting, induced the outgrowth of a limited number of axillary buds (the number of which was species specific) at the nodes immediately distal to the newly established root, thereby indicating a phenotypic response similar to that in T. repens. Furthermore, their branching responses to manipulative treatments were also similar to those of T. repens, indicating that their regulatory physiology of axillary bud outgrowth from their prostrate stems is similar. We conclude that, for the group of prostrate nodally rooting clonal herbs as a whole, the apical dominance phenotype arises predominantly from variation in the supply of resources from nodal roots rather than from repression of axillary buds by apical tissues (apical dominance). We suggest that evolution of such a physiological mechanism enhances the exploration for patchily distributed favourable nodal rooting sites by regulating shoot development so as to efficiently utilise the diminishing intra-plant availability of root-supplied resources. For the species examined, inter-specific variation in intensity of branching response to a nodal root is shown to be linked to a trade off in foraging strategy, with the allocation of resources primarily to explorative growth (long internodes, few branches) in guerilla species or to exploitive growth (short internodes, many branches) in phalanx species.Co-ordinating editor: J. Tuomi     

Polyamines in grapevine microcuttings cultivated in vitro. Effects of amines and inhibitors of polyamine biosynthesis on polyamine levels and microcutting growth and development

The main free amines identified during growth and development of grapevine microcuttings of rootstock 41 B, (Vitis vinifera cv. Chasselas × Vitis berlandieri) cultivated in vitro were agmatine, putrescine, spermidine, spermine, diaminopropane and tyramine (an aromatic amine). Amine composition differed according to tissue, with diaminopropane the major polyamine in the apical parts, internodes and leaves. Putrescine predominated in the roots. There was also a decreasing general polyamine and specific tyramine gradient along the stem from the top to the bottom. Conjugated amines were only found in roots. The application of exogenous amines (agmatine, putrescine, spermidine, tyramine) stimulated development and growth of microcuttings, suggesting that the endogenous concentrations of these amines can be growth limiting. Diaminopropane (the product of oxidation of spermidine or spermine by polyamine oxydases) strongly inhibited microcutting growth and development. -DL-difluoromethylarginine (DFMA), a specific and irreversible inhibitor of the putrescine-synthesizing enzyme, arginine decarboxylase (ADC), led to inhibition of microcutting development. Application of agmatine or putrescine to the inhibited system resulted in a reversal of inhibition indicating that polyamines are involved in regulating the growth and development of grapevine microcuttings. -DL-difluoromethylornithine (DFMO), a specific and irreversible inhibitor of putrescine biosynthesis from ornithine decarboxylase (ODC), had no effect on microcutting development and growth. We propose that ADC regulates putrescine biosynthesis during microcutting development.     

Mutation of glutamic acid 103 of toluene o-xylene monooxygenase as a means to control the catabolic efficiency of a recombinant upper pathway for degradation of methylated aromatic compounds

Toluene o-xylene monooxygenase (ToMO) and phenol hydroxylase (PH) of Pseudomonas stutzeri OX1 act sequentially in a recombinant upper pathway for the degradation of aromatic hydrocarbons. The catalytic efficiency and regioselectivity of these enzymes optimize the degradation of growth substrates like toluene and o-xylene. For example, the sequential monooxygenation of o-xylene by ToMO and PH leads to almost exclusive production of 3,4-dimethylcatechol (3,4-DMC), the only isomer that can be further metabolized by the P. stutzeri meta pathway. We investigated the possibility of producing ToMO mutants with modified regioselectivity compared with the regioselectivity of the wild-type protein in order to alter the ability of the recombinant upper pathway to produce methylcatechol isomers from toluene and to produce 3,4-DMC from o-xylene. The combination of mutant (E103G)-ToMO and PH increased the production of 4-methylcatechol from toluene and increased the formation of 3,4-DMC from o-xylene. These data strongly support the idea that the products and efficiency of the metabolic pathway can be controlled not only through mutations that increase the catalytic efficiency of the enzymes involved but also through tuning the substrate specificity and regioselectivity of the enzymes. These findings are crucial for the development of future metabolic engineering strategies.     

Mutation of Glutamic Acid 103 of Toluene o-Xylene Monooxygenase as a Means To Control the Catabolic Efficiency of a Recombinant Upper Pathway for Degradation of Methylated Aromatic Compounds

Toluene o-xylene monooxygenase (ToMO) and phenol hydroxylase (PH) of Pseudomonas stutzeri OX1 act sequentially in a recombinant upper pathway for the degradation of aromatic hydrocarbons. The catalytic efficiency and regioselectivity of these enzymes optimize the degradation of growth substrates like toluene and o-xylene. For example, the sequential monooxygenation of o-xylene by ToMO and PH leads to almost exclusive production of 3,4-dimethylcatechol (3,4-DMC), the only isomer that can be further metabolized by the P. stutzeri meta pathway. We investigated the possibility of producing ToMO mutants with modified regioselectivity compared with the regioselectivity of the wild-type protein in order to alter the ability of the recombinant upper pathway to produce methylcatechol isomers from toluene and to produce 3,4-DMC from o-xylene. The combination of mutant (E103G)-ToMO and PH increased the production of 4-methylcatechol from toluene and increased the formation of 3,4-DMC from o-xylene. These data strongly support the idea that the products and efficiency of the metabolic pathway can be controlled not only through mutations that increase the catalytic efficiency of the enzymes involved but also through tuning the substrate specificity and regioselectivity of the enzymes. These findings are crucial for the development of future metabolic engineering strategies.     

Resistance and response of <Emphasis Type="Italic">Pinus pinaster</Emphasis> seedlings to <Emphasis Type="Italic">Hylobius abietis</Emphasis> after induction with methyl jasmonate

Experimental induction of plant chemical defences with methyl jasmonate (MeJa) is a valuable tool for understanding the ecology of plant defensive responses. However, few studies have examined whether MeJa-induced defences in conifers are effective against insect herbivores. We studied, in 17 half-sib Pinus pinaster families, (i) the effect of MeJa application on plant growth and on the induction of diterpenoid resin in different sections of the stem; (ii) whether MeJa-induced defences increase the resistance of living pine juveniles against the large pine weevil Hylobius abietis in an in vivo bioassay and (iii) the induction of resin content after weevil wounding. Resin concentration was greater in the upper section of the stem compared with basal sections in both MeJa-induced and non-induced seedlings. Sixty days after MeJa application, treated plants showed 40% greater resin content all along the stem, but reduced height growth compared to control plants. MeJa-induction was effective against the pine weevil, as induced seedlings were 21% less damaged than control plants. Wounding activity by H. abietis produced a strong local defensive response after 48 h, where resin concentration was double that observed in the basal and apical sections not exposed to the insects.     

The effect of stem and cob borers on maize subjected to different nitrogen treatments

The influence of four nitrogen levels (0, 60, 90 and 120 kg N/ha) on growth of maize and development of lepidopterous pests was investigatdd in a field trial. Nitrogen had a positive effect on both plant growth variables (plant height, stem diameter and yield), and development and survival ofSesamia calamistis andEldana saccharina, and thereby increased the incidence of dead hearts and stem tunneling. However, the percent yield loss due to artificial infestation decreased with increasing N application rate from 20% to 11% in the in the 0kg/ha and 120kg/ha treatment, respectively. Using a multiple regression analysis, plant height, plant diameter and stem tunneling were found to be the most important variables explaining the variability in maize yield.     

不同生物有机肥对连作菠萝生长及防控心腐病效果

[背景] 菠萝心腐病是菠萝生产中常见的土传病害。[目的] 促进连作菠萝的高效栽培并提高病害防效。[方法] 采集连作发病菠萝园土壤,利用盆栽实验研究3种载体（椰糠、泥炭土、菜籽饼）和生防菌株（枯草芽孢杆菌HL2、链霉菌株HL3）与商品普通有机肥共同堆制成的生物有机肥对菠萝植株生长及菠萝心腐病防控效果的影响。[结果] 与化肥处理（CK）相比,施用生物有机肥处理能促进菠萝植株的生长,显著增加鲜重（叶、茎、根）、干重（叶、茎、根）和D叶长（菠萝植株叶片束起时最长的叶片长度）;与化肥处理（CK）相比,施用生物有机肥处理均能降低菠萝心腐病发病率;施用商品普通有机肥处理（YJ）防病能力较差,而生物有机肥处理（KC）的防控效果最好,其次为生物有机肥处理（KY、KN、LY）,防控效果均为83.5%。相关分析表明,土壤病原菌（烟草疫霉菌）含量与放线菌、有机质、pH呈极显著负相关关系（p<0.001）,与土壤速效钾含量呈显著正相关关系（p<0.05）,与发病率呈显著正相关关系（p<0.01）。[结论] 施用生物有机肥可促进菠萝植株生长、降低发病率,对菠萝心腐病有较好的防效,可为菠萝产业健康发展提供参考。     

天然沙冬青器官生态化学计量特征对异质生境的响应

以我国重点保护的珍稀濒危植物且是西北荒漠地区唯一常绿阔叶灌木沙冬青（Ammopiptanthus mongolicus）为研究对象,分析异质性荒漠生境（固定沙地、半固定沙地、石质沙地、洪积砾石坡地和盐碱滩地）对沙冬青叶、茎、根、花和种子生态化学计量学特征的影响,了解其生长的适应机制和生存策略。结果表明：沙冬青各器官碳（C）含量表现为叶 > 茎 > 根 > 种子 > 花,而氮（N）、磷（P）、钾（K）营养元素含量均表现为种子 > 花 > 叶 > 根 > 茎,N、P、K三大营养元素在繁殖器官中的富集,可以促进沙冬青由营养生长向生殖生长的转变,反映了资源分配模式和植物生长策略。沙冬青各器官的碳氮磷钾含量和各元素化学计量比在不同生境条件下变化较复杂,其中在沙质土壤（固定和半固定沙地）具有更高的C、N、P储存能力,而K在砾质土壤（石质沙地和洪积砾石坡地）含量较高,且砾质荒漠沙冬青的C：N、C：P 及 N：P 均显著高于沙质土壤,表明沙冬青在石质沙地和洪积砾石坡地有更高的养分利用效率。各器官元素含量相关分析表明器官间的养分协同性远高于器官内部。化学计量比C：N、C：P、C：K均表现为：茎 > 根 > 叶 > 花 > 种子,N：P为根 > 叶 > 茎 > 花 > 种子,N：K为茎 > 根 > 叶 > 种子 > 花,K：P 为叶 > 根 > 种子 > 茎 > 花,各器官中的C：N和N：P比在各生境间相对较稳定,而K：P比变化巨大,N：P与P含量呈显著的负相关（P <0.05）,与N含量的相关性不显著（P >0.05）,说明P作为敏感性元素决定了沙冬青体内N：P比值的变化,且不同生境叶片N：P比值均大于16,说明沙冬青生长主要受P限制。器官与生境对沙冬青化学计量特征都有影响,生境对C含量和N：K、K：P的影响较大,器官对N、P、K含量及C：N、C：P、C：K、N：P的影响较大。除P元素外,各元素含量及其化学计量比均受器官和生境交互作用影响。了解植物根-茎-叶-花-种子的整体资源权衡和协变策略,为沙冬青物种资源的保护和开发提供理论依据。     

Action du CCC et du B 995 sur la mise à fleur d'une plante bisannuelle,l'Œnothera biennis

Summary Oenothera biennis L. is a typical biennial plant with an absolute cold requirement for subsequent floral initiation under long-day conditions. Flowering of vernalized Oe. biennis is associated with transition from a rosette habit to the formation of a long flower-bearing stem. Vernalization in Oe. biennis consists of two consecutive stages: (1) preparation for flowering; (2) preparation of stem elongation. At the end of the second stage, the level of endogenous gibberellin-like substances is sufficient to allow the stem elongation which is requisite for subsequent floral development.Applications of (2-chloroethyl)trimethylammonium chloride (CCC) via the roots, when made after the cold treatment, have no effect on internodal elongation and subsequent flowering of vernalized Oe. biennis. Relatively small amounts of CCC applied onto the apical bud of the rosette promote stem growth. However, 750 g of CCC act as a growth inhibitor and delay the beginning of stem elongation but this retardant has no effect on the number of flower buds.In contrast, N-dimethylaminosuccinamic acid (B 995), when applied after a cold treatment, delays the beginning of stem growth, this delay increasing with greater amounts of applied B 995. However, with relatively small amounts of B 995, the rate of later stem growth increases rapidly so that treated plants flower at the same time as controls.If gibberellic acid (GA₃) is applied on the apical bud just at the same time as B 995, it reverses the effects of the growth retardant, even when the amount of B 995, applied by itself, is sufficient to inhibit entirely stem elongation and flowering.B 995 is particularly effective if the preceding cold treatment was just sufficient for effective vernalization. If the cold treatment was extended beyond this time, a greater amount of retardant was required to obtain the same degree of stem growth inhibition.B 995 probably acts by interference with the metabolism of endogenous gibberellin-like substances. The delay of floral initiation in vernalized Oe. biennis by B 995 is a consequence of the retarded internode elongation; if this retardation exceeds a certain limit, the plant is devernalized and exhibits a cold requirement identical with the original one.     

Phytochemical Investigation of Cuscuta campestris Yunck. Stem Extract and Evaluation of Its Bioherbicidal Effect on Amaranthus retroflexus L. and Portulaca oleracea L

This study focused on characterizing chemically and evaluating in vitro allelopathic and bioherbicidal potential of secondary metabolites extracted from the stem of Cuscuta campestris in seed germination, early seedling growth and early plant growth of Amaranthus retroflexus and Portulaca oleracea. The combined effects of stem extract and a reduced dose of herbicide metribuzin were also examined. Plant extract contained 17 phenolic compounds and the most abundant phenols were flavonoids: quercetin, (+)-catechin, daidzin, luteolin, and rutin. The seeds of P. oleracea were less sensitive than the seeds of A. retroflexus. The seed bioassay confirmed the inhibitory effect of stem extract on germination and early growth of both weed seedlings at concentrations of 0.75 % and 1 %, and a minor inhibitory effect in the plant bioassay. On the other hand, a synergy of C. campestris stem extract and metribuzin was revealed, as their combination achieved better results in the control of both weed species. Based on obtained data C. campestris stem extract could be a potential source of natural-based weed control molecules.     

The role of phytochrome B,D and E in thermoperiodic responses of <Emphasis Type="Italic">Arabidopsis thaliana</Emphasis>

The objective of this work was to study the role of the phytochromes (phy) B, D and E in the thermoperiodic control of elongation and flowering time in Arabidopsis thaliana. WT, and phyB, phyD and phyE single mutants, and phyB phyD and phyB phyE double mutants, were grown under day/night temperatures (DT/NT) of 12/22°C, 17/17°C or 22/12°C (negative, zero and positive DIF, respectively) for inflorescence stem length measurements, and under DT/NT 17/25°C or 25/17°C (negative and positive DIF, respectively) for leaf morphology and flowering time measurements. In WT final length of the stem, petiole and leaf blade were longer under positive DIF compared to negative DIF. The temperature effect was stronger in the leaf petiole than the stem, whereas only a slight change was seen in the leaf blade length direction and none in the width direction. The temperature effect on stem and petiole elongation was reduced or nearly eliminated in the genotypes lacking phyB, while a phyD or a phyE mutation had no influence or a slightly positive influence on the temperature effect, respectively. These results suggest that phyB, and not phyD or phyE, is needed for a complete thermoperiodic control of elongation growth in A. thaliana. For all genotypes tested, plants flowered earlier at negative DIF than positive DIF, suggesting that none of the three phytochromes B, D, or E is needed for a thermoperiodic control of flowering time in A. thaliana.     

Diversity of Mechanical Architectures in Climbing Plants: An Evolutionary Perspective

Mechanical architectures of a wide range of climbing plants are reviewed from a wide phylogenetic range and evolutionary contingencies. They include an herbaceous lycopod (Lycopodiaceae) - a woody tropical liana (Apocynaceae), temperate climbers, herbs and shrubs (Ranunculacae), and two representative climbing palms (Arecoideae, Calamoideae). Trends in mechanical properties during development are reviewed and interpreted via changes in anatomical development of the stem and type of connection to host supports. The results indicate that there are some biomechanical features common to diverse climbing plants including (1) phases of relatively rigid stem growth where the climbing stem has to span between supports and (2) a mechanism to achieve greater compliancy towards the base or at points where the slender climbing stem is at risk from excessive mechanical stress. Evolutionary contingencies such as basal plesiomorphic constraint, complexification, simplification and developmental loss can drastically influence ways in which different plants have evolved different biomechanical climbing architectures. Two key developmental features controlling the biomechanics of the climbing stem are (1) the presence/absence of secondary growth and (2) the number, complexity and coordination of development of primary or secondary tissues with varying mechanical properties. Recent research has suggested that evolution of specialized climbing architectures can canalize subsequent evolution of alternative growth forms. The results suggest that the origin and type of climbing architecture can be heavily influenced by ancestral growth forms and architectures. Despite the extremely complex patterns of plant growth form evolution involving escapes to and from more specialized or simpler bauplans, selective pressure towards non-self-supporting growth forms is a remarkably persistent and iterative feature of growth form evolution in land plants.     

Inhibition of stem growth and gibberellin production in Agrostemma githago L. by the growth retardant tetcyclacis

The effects of the new growth retardant tetcyclacis (TCY) on stem growth and endogenous gibberellin (GA) levels were investigated in the long-day rosette plant Agrostemma githago. Application of TCY (10 ml of a 5·10^-5M solution daily) to the soil suppressed stem elongation in Agrostemma grown under long-day conditions. A total of 10 g GA₁ (1 g applied on alternate days) per plant overcame the growth retardation caused by TCY.Control plants and plants treated with TCY were analyzed for endogenous GAs after exposure to nine long days. The acidic extracts were fractionated by high-performance liquid chromatography. Part of each fraction was tested in the d-5 maize bioassay, while the remainder was analyzed by combined gas chromatography-selected ion monitoring. The bioassay results indicated that the GA content of plants treated with TCY was much lower than that of untreated plants. The data obtained by gas chromatography-selected ion monitoring confirmed that the levels of seven GAs present in Agrostemma were much reduced in TCY-treated plants when compared with the levels in control plants: GA₅₃ (13%), GA₄₄ (0%), GA₁₉ (1%), GA₁₇ (33%), GA₂₀ (15%), GA₁ (4%), and epi-GA₁ (13%). These results provide evidence that TCY inhibits stem growth in Agrostemma by blocking GA biosynthesis and thus lowering the levels of endogenous GAs.Abbreviations AMO-1618 2-isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine-carboxylate methyl chloride - GA(s) gibberellin(s) - HPLC high-performance liquid chromatography - TCY Tetcyclacis (5-[4-chlorophenyl]-3,4,5,9,10-pentaaza-tetracyclo-5,4,1,0^2,6,0^8,11-dodeca-3,9-diene)     

Oncostatin M inhibits differentiation of rat stem Leydig cells in vivo and in vitro

Oncostatin M (OSM) is a pleiotropic cytokine within the interleukin six family of cytokines, which regulate cell growth and differentiation in a wide variety of biological systems. However, its action and underlying mechanisms on stem Leydig cell development are unclear. The objective of the present study was to investigate whether OSM affects the proliferation and differentiation of rat stem Leydig cells. We used a Leydig cell regeneration model in rat testis and a unique seminiferous tubule culture system after ethane dimethane sulfonate (EDS) treatment to assess the ability of OSM in the regulation of proliferation and differentiation of rat stem Leydig cells. Intratesticular injection of OSM (10 and 100 ng/testis) from post‐EDS day 14 to 28 blocked the regeneration of Leydig cells by reducing serum testosterone levels without affecting serum luteinizing hormone and follicle‐stimulating hormone levels. It also decreased the levels of Leydig cell‐specific mRNAs (Lhcgr, Star, Cyp11a1, Hsd3b1, Cyp17a1 and Hsd11b1) and their proteins by the RNA‐Seq and Western blotting analysis. OSM had no effect on the proliferative capacity of Leydig cells in vivo. In the seminiferous tubule culture system, OSM (0.1, 1, 10 and 100 ng/mL) inhibited the differentiation of stem Leydig cells by reducing medium testosterone levels and downregulating the expression of Leydig cell‐specific genes (Lhcgr, Star, Cyp11a1, Hsd3b1, Cyp17a1 and Hsd11b1) and their proteins. OSM‐mediated action was reversed by S3I‐201 (a STAT3 antagonist) or filgotinib (a JAK1 inhibitor). These data suggest that OSM is an inhibitory factor of rat stem Leydig cell development.     

Climatic influences on intra-annual stem radial increment of Pinus sylvestris (L.) exposed to drought

Within a dry inner Alpine valley in the Eastern Central Alps (750 m a.s.l., Tyrol, Austria), the influence of climate variables (precipitation, air humidity, temperature) and soil water content on intra-annual dynamics of tree-ring development was determined in Scots pine (Pinus sylvestris L.) at two sites differing in soil water availability (xeric and dry-mesic site). Radial stem development was continuously followed during 2007 and 2008 by band dendrometers and repeated micro-sampling of the developing tree rings of mature trees. Daily and seasonal fluctuations of the stem radius, which reached almost half of total annual increment, primarily reflected changes in tree water status and masked radial stem growth especially during drought periods in spring. However, temporal dynamics of intra-annual radial growth determined by both methods were found to be quite similar, when onset of radial growth in dendrometer traces was defined by the occurrence of first enlarging xylem cells. Radial increments during the growing period, which lasted from early April through early August, showed statistically significant relationships with precipitation (Kendall τ = 0.234, p < 0.01, and τ = 0.184, p < 0.05, at the xeric and dry-mesic site, respectively) and relative air humidity (Pearson r = 0.290, p < 0.05, and r = 0.306, p < 0.05 at the xeric and dry-mesic site, respectively). Soil water content and air temperature had no influence on radial stem increment. Culmination of radial stem growth was detected at both study plots around mid-May, prior to occurrence of more favourable climatic conditions, i.e., an increase in precipitation during summer. We suggest that the early decrease in radial growth rate is due to a high belowground demand for carbohydrates to ensure adequate resource acquisition on the drought-prone substrate.     

Effect of plant characteristics of jute varieties on incidence of pests in West Bengal,India

This study was conducted with a view to understand the effect of plant characteristics on the incidence of pests on most popular jute varieties, viz. JRO-524, JRO-632, JRO-878, JRO-7835 of olitorius jute and JRC-212, JRC-321, JRC-4444, JRC-7447 of capsularis jute. Correlation studies of plant characteristics with pest incidence in jute (Corchorus spp.) revealed that the basal girth of plant exhibited a positive significant relationship with the incidence of Apion corchori Marshall but not with other pests such as jute semilooper (Anomis sabulifera Guen.), Bihar hairy caterpillar (Spilarctia obliqua Wlk.), grey weevil (Myllocerus discolor Bohemus) and yellow mite (Polyphagotarsonemus latus Banks). However, plant height showed positive correlation with the incidence of all the major pests of jute. Leaf characteristics (number of leaves/plant, leaf area, leaf thickness, moisture and chlorophyll content of leaves of all the varieties recorded at three different growth stages, i.e. at 50, 80 and 110 days after sowing), number of leaves/plant had positive and significant relationship with the incidence of all the pests except stem weevil. However, leaf area and moisture content of leaves showed significant positive relationship with the incidence of yellow mite. Leaf moisture also showed a positive role on the infestation of grey weevil. Leaf thickness and chlorophyll content of leaves and stem, fibre thickness and moisture content of stem did show any significant effect on pest's incidence. Upon comparing the plant characteristics between the two jute species, olitorius varieties had greater fibre thickness than that of capsularis varieties but fibre thickness had no significant impact on incidence of pests.     

不同生境下空心莲子草响应模拟昆虫采食的生长和化学防御策略

外来植物往往可以入侵多种生境并受到多种昆虫的采食,而不同生境条件将可能会影响这些入侵植物对昆虫采食的防御策略。以入侵我国的克隆植物——空心莲子草为研究对象,分别选择生长在水生生境、水陆两栖生境和陆生生境中的无性个体(分株),通过50%去叶处理模拟昆虫采食,分析不同生境下空心莲子草对模拟昆虫采食处理的生长及化学防御响应的差异。模拟昆虫采食处理显著抑制了陆生生境、水陆两栖生境以及水生生境下空心莲子草的根、茎、叶和总生物量,但对3种生境下空心莲子草的生物量分配(根冠比、根生物量分配、茎生物量分配和叶生物量分配)均无显著影响。陆生生境下空心莲子草根、茎和总生物量显著高于水陆两栖生境和水生生境,根冠比显著低于水陆两栖生境和水生生境。模拟昆虫采食处理显著降低了空心莲子草的木质素含量,而对单宁和总酚含量影响不显著。生境对木质素含量无显著影响,但陆生生境下空心莲子草单宁含量显著高于水陆两栖生境和水生生境,且总酚含量显著高于水陆两栖生境,表明陆生生境中空心莲子草具有更强的防御能力。空心莲子草木质素含量与总生物量无显著相关性,但在模拟采食情况下,其总酚含量与总生物量呈显著负相关,而无论模拟昆虫采食处理存在与否,空心莲子草单宁含量与总生物量均呈显著正相关。因此,空心莲子草存在昆虫介导的生长和化学防御之间的权衡,在昆虫采食的情况下可通过减少生长来增加对化学防御物质的投入,但生境对空心莲子草这种生长-防御权衡的影响十分有限。     

Stimulatory effects of jasmonic acid on potato stem node and protoplast culture

The effect of jasmonic acid (JA), in a wide range of concentrations (0.01–100 M), on the development of potato plantlets (Solanum tuberosum L.cv. Vesna) was investigated in order to discriminate between physiological and supraoptimal effects of this growth regulator in vitro. Concentrations from 0.1–1 M significantly increased the length of developed plants. Application of JA in these concentrations resulted in a very well differentiated root system with many lateral branches. With increasing JA concentrations, the main roots shortened and thickened. Concentrations higher than 10 M led to the compaction of the stem, roots, and root hairs, giving a stunted appearance to the plants. The effect of JA on cell wall regeneration and callus formation was observed in potato leaf protoplast culture. JA at concentrations from 0.01–1 M stimulated cell division and microcalli development.     

Evaluation of wheat cultivars for ability to retard development of stem rust

The ability of wheat cultivars (Triticum aestivum) to retard the development of stem rust, Puccinia graminis f.sp. tritici, was evaluated in hill plots for 3 yr at several locations in Minnesota, against single races and mixtures of races. The area under the disease progress curve was a convenient and reliable method for data summation, but the rate of disease development was not. When inoculated with single races (15B2, 32, 113 or 31) or with mixtures of races (11, 15, 15B2, 17, 32, 151), the cvs Exchange, Thatcher, McMurachy, Redman, Kenya 58, Frontana and Idaed retarded stem rust development more than Baart, Prelude and Marquis; Lee was intermediate. The methods and techniques reported should permit selection of cultivars capable of retarding the development of stem rust.