Complexity untwined: The structure and function of cucumber (Cucumis sativus L.) shoot phloem

Cucurbit phloem is complex, with large sieve tubes on both sides of the xylem (bicollateral phloem), and extrafascicular elements that form an intricate web linking the rest of the vasculature. Little is known of the physical interconnections between these networks or their functional specialization, largely because the extrafascicular phloem strands branch and turn at irregular angles. Here, export in the phloem from specific regions of the lamina of cucumber (Cucumis sativus L.) was mapped using carboxyfluorescein and ¹⁴C as mobile tracers. We also mapped vascular architecture by conventional microscopy and X-ray computed tomography using optimized whole-tissue staining procedures. Differential gene expression in the internal (IP) and external phloem (EP) was analyzed by laser-capture microdissection followed by RNA-sequencing. The vascular bundles of the lamina form a nexus at the petiole junction, emerging in a predictable pattern, each bundle conducting photoassimilate from a specific region of the blade. The vascular bundles of the stem interconnect at the node, facilitating lateral transport around the stem. Elements of the extrafascicular phloem traverse the stem and petiole obliquely, joining the IP and EP of adjacent bundles. Using pairwise comparisons and weighted gene coexpression network analysis, we found differences in gene expression patterns between the petiole and stem and between IP and EP, and we identified hub genes of tissue-specific modules. Genes related to transport were expressed primarily in the EP while those involved in cell differentiation and development as well as amino acid transport and metabolism were expressed mainly in the IP.     

Efficacy of Fluensulfone in a Tomato–Cucumber Double Cropping System

Vegetable crops in the southeastern United States are commonly grown on plastic mulch with two crop cycles produced on a single mulch application. Field trials were conducted in 2013 and 2014 in two locations to evaluate the efficacy of fluensulfone for controlling Meloidogyne spp. when applied through drip irrigation to cucumber in a tomato–cucumber double-cropping system. In the spring tomato crop, 1,3-dichloropropene (1,3-D), fluensulfone, and a resistant cultivar significantly decreased root galling by 91%, 73%, and 97%, respectively, compared to the untreated control. Tomato plots from the spring were divided into split plots for the fall where the main plots were the spring treatment and the subplots were cucumber either treated with fluensulfone (3.0 kg a.i./ha. via drip irrigation) or left untreated. The fall application of fluensulfone improved cucumber vigor and reduced gall ratings compared to untreated subplots. Fluensulfone reduced damage from root-knot nematodes when applied to the first crop as well as provided additional protection to the second crop when it was applied through a drip system.     

Enantioselective Degradation of Chiral Insecticide Dinotefuran in Greenhouse Cucumber and Soil

The enantioselective degradation behavior of the chiral insecticide dinotefuran in cucumber and soil was investigated under greenhouse conditions based on the method established with a normal‐phase high‐performance chromatography (HPLC) on a ChromegaChiral CCA column (250 × 4.6 mm, 5 µm, ES Industries). The linearity range, matrix effect, precision, and accuracy of the method were evaluated and the method was then successfully applied for the enantioselective analysis of dinotefuran in cucumber and soil. Significant enantioselectivity of degradation was observed in soil according to the results. The (+)‐dinotefuran was more persistent in soil with half‐life of 21.7 d, which is much longer than that of (–)‐dinotefuran (16.5 d). In cucumber, the (–)‐dinotefuran also tended to be preferentially degraded both in foliar and douche treatment. However, the statistical analysis indicated the enantioselectivity of degradation in cucumber was not significant. The research provides the first report concerning the enantioselective degradation of dinotefuran enantiomers and the results can be used for understanding the insect‐controlling effect and food safety evaluation. Chirality 27:137–141, 2015. © 2014 Wiley Periodicals, Inc.     

森林演替对都江堰鼠类多样性的影响

为深入了解森林演替对野生动物群落结构和多样性格局的影响,于2012—2013年在四川省都江堰般若寺林场选择5种森林演替阶段(0~5、6~10、11~20、21~30 a和天然次生林(100 a),共计21个样地)对鼠类多样性进行调查。本次调查累计捕获鼠类9种,其中仓鼠科1种,鼠科8种。5种森林演替阶段共有物种有针毛鼠(Niviventer fulvescens)、中华姬鼠(Apodemus draco)、社鼠(N.confucianus)、高山姬鼠(A.chevrieri)和大耳姬鼠(A.latronum)。不同森林演替阶段之间的鼠类物种数、个体数和多样性特征差异不显著,但天然次生林中的鼠类个体数略高于其他演替阶段。多元统计分析(NMDS和CCA排序)表明,不同森林演替阶段的鼠类群落组成相似性较高,但灌木层和草本层盖度等生境因子可影响鼠种的分布。除高山姬鼠、针毛鼠和中华姬鼠等分布较广的种类外,其他种类对微生境有一定的选择倾向。小泡巨鼠(Leopoldamys edwardsi)主要生活于演替期长的天然次生林中,社鼠和大耳姬鼠主要分布在灌木层盖度较高的生境,巢鼠(Micromys minutus)和黑腹绒鼠(Eothenomys melanogaster)主要生活在草本层盖度较高的生境,大足鼠(Rattus nitidus)适于生活在草本层和灌木层盖度均适中的生境。综上所述,不同森林演替阶段之间的鼠类多样性差异较小,但森林演替所造成的微生境变化可能影响鼠类物种的分布和多样性格局。     

鹅掌楸苗期动态生命表

报道了鹅掌楸在苗圃播种后的出苗率和幼苗存活率,根据定期观察数据编制了苗期动态生命表。结果表明,4个种源的出苗率都很低(1.64%～3.05%),比其各自的饱满种子率低得多;天然种源的出苗率高于栽培的种源,但前者的出苗数占饱满种子数的比例却低于后者。至一个生长季以后,幼苗存活率仅占出苗数的16%～27%,而黄山种源与庐山种源的交配后代则高达60%,明显地高于其亲本和其它种源。种子大小对于出苗率和幼苗存活率没有直接影响。最后讨论了遗传因素和生存环境对幼苗存活的影响,并认为种子和幼苗适合度低是鹅掌楸致濒的重要原因之一。     

Evidence for matrotrophy in the viviparous sea cucumber Leptosynapta clarki: A role for the genital haemal sinus?

Summary

Viviparity, where the embryos develop in the female reproductive system, is a rare form of reproduction in marine invertebrates, being described in only 14 species of echinoderm. In the intraovarian brooding sea cucumber, Leptosynapta clarki Heding 1928 (cf., Sewell et al. 1995), we used direct evidence (changes in energetic content) to show that significant additional nutrients are provided to the embryos during viviparous development (matrotrophy). In the transition from a structure used to produce gametes to a long-term brooding structure there are visual, histological and transmission electron microscopy (TEM) changes in the structure of the ovarian wall. Changes occur primarily in the cells of the visceral peritoneum and involve an increase in size of the connective tissue/genital haemal sinus (CT/GHS). In the latter part of the brooding period the visceral peritoneum returns to a flattened form, and new oocytes develop along the tubule wall. Similar changes in the intraovarian brooding sea cucumber Oneirophanta mutabilis affinis lead us to suggest that there is a role for the genital haemal sinus in providing nutrition during the brooding period in viviparous echinoderms. Future research is suggested to focus on changes in the ovarian wall structure during the different phases of reproduction (gamete production/brooding) in these species.     

Antiviral properties and interaction of novel chalcone derivatives containing a purine and benzenesulfonamide moiety

A new concise and facile method was explored to synthesize a series of novel chalcone derivatives containing a purine and benzenesulfonamide moiety and their antiviral properties were evaluated against TMV and CMV. Biological assays indicated that several of the derivatives exhibited significant anti-TMV and anti-CMV activities in vivo. In particular, compound d2 displayed excellent inactivating activity against TMV, with the EC₅₀ value of 51.65?μg/mL, which was better than that of ribavirin (150.45?μg/mL). Molecular docking showed that there are four hydrogen bonds between compound d2 and TMV coat protein (TMV-CP). Compound d2 demonstrated strong binding capacity to TMV-CP with K_a?=?1.58?×?10⁵?L/mol and K_d?=?12.16?μM. These findings indicated that chalcone derivatives are worthy of further research and development as templates for new antiviral agents.     

Life history ofAphis gossypii on cucumber: influence of temperature, host plant and parasitism

Life table data forAphis gossypii Glover (Homoptera: Aphididae), an important pest in glasshouse cucumber crops, were studied at 20, 25 and 30°C on two cucumber cultivars (Cucumis sativus L.) in controlled climate cabinets. The development time on the cucumber cv. ‘Sporu’ ranged from 4.8 days at 20°C to 3.2 days at 30°C. Immature mortality was approximately 20% and did not differ between temperatures. Most mortality occurred during the first instar. Reproduction periods did not differ among temperatures, but at 25 and 30°C more nymphs were produced (65.9 and 69.8 nymphs/♀, respectively) than at 20°C (59,9 nymphs/♀) because of a higher daily reproduction. Intrinsic rate of increase was greatest at 25°C (r _m =0.556 day⁻¹). At 20 and 30°C the intrinsic rate of increase was 0.426 and 0.510, respectively. On cv. ‘Aramon’, the development time ofA. gossypii was approximately 20% longer at all temperatures. Immature mortality did not differ between the two cultivars. The intrinsic rate of increase on cv. ‘Aramon’ was 15% smaller than on cv. ‘Sporu’. The use of cucumber cultivars partially resistant to aphids is discussed in relation to biological control of cotton aphid in glasshouses. Development time and immature mortality on leaves of the middle and upper leaf layer of glasshouse grown cucumber plants (cv. ‘Aramon’) were comparable to development in the controlled climate cabinets. On the lower leaves immature mortality was much higher (approximately 82%) than on leaves of the middle (24.0%) and upper leaf layer (24.5%). Reproduction was less on the lower leaf layer (45.9, 70.5 and 70.1 nymphs/♀ on leaves of the lower, middle and upper leaf layer, respectively). Aphids, successfully parasitized byAphidius colemani Viereck (Hymenoptera: Braconidae) only reproduced when they were parasitized after the third instar. Fecundity was 0.1 to 0.9 and 10.5 to 13.3 nymphs/♀ for aphids parasitized in the fourth instar or as adults, respectively. Reproduction of aphids that were stung but survived the attack was lower than for aphids not stung. Average longevity of these aphids was equal to the longevity of aphids not stung byA. colemani.     

In vitro decondensation of the sperm chromatin in Holothuria tubulosa (sea cucumber) not affecting proteolysis of basic nuclear proteins

Sea urchin and sea star oocyte extracts contain proteolytic activities that are active against sperm basic nuclear proteins (SNBP). This SNBP degradation has been related to the decondensation of sperm chromatin as a possible model to male pronuclei formation. We have studied the presence of this proteolytic activity in Holothuria tubulosa (sea cucumber) and its possible relationship with sperm nuclei decondensation. The mature oocyte extracts from H. tubulosa contain a proteolytic activity to SNBP located in the macromolecular fraction of the egg‐jelly layer. SNBP degradation occurred both on sperm nuclei and on purified SNBP, histones being more easily degraded than protein Ø_o (sperm‐specific protein). SNBP degradation was found to be dependent on concentration, incubation time, presence of Ca²⁺, pH, and this activity could be a serine‐proteinase. Thermal denaturalization of the oocyte extracts (80°C, 10–15 min) inactivates its proteolytic activity on SNBP but does not affect sperm nuclei decondensation. These results would suggest that sperm nuclei decondensation occurs by a mechanism different from SNBP degradation. Thus, the sperm nuclei decondensation occurs by a thermostable factor(s) and the removal of linker SNBP (H1 and protein Ø_o) will be a first condition in the process of sperm chromatin remodeling.     

An improvement of cucumber cotyledon greening bioassay for cytokinins

The cucumber cotyledon greening bioassay for cytokinins was modified by using 95% acetone-ethanol instead of 80% acetone as extraction solvent. The cotyledons were extracted directly with a 2:1 (v/v) acetone-ethanol solution in dark for 24 hours, omitting the homogenization and centrifugation operations of the previous bioassay. The modified bioassay is more convenient and especially useful in screening cytokinin-active substance from a large number of samples.