马尾松红锥混交林现状分析与评价

本文根据广西六万林场马尾松、红锥混交林的调查结果,分析了松、锥混交林各树种的胸径、树高和材积的生长现状;土壤的理化特性;松锥混交林营造技术措施。并对该场松锥混交林存在的问题,初步探讨了松锥混交林合理的种间关系和营林的主要技术措施。     

Variation in horizontal and vertical transmission of the endophyte Epichloë elymi infecting the grass Elymus hystrix

Systemic fungal endophytes (Clavicipitaceae) of grasses reproduce sexually when the fungus forms stromata and contagious ascospores, or asexually by vertical transmission of hyphae into seeds and seedlings. Vertical transmission is predicted to favor reduced virulence compared with horizontal transmission in systems with both types of transmission. Here, variation in vertical and horizontal transmission and its potential heritability in a host grass-endophyte interaction, Elymus hystrix infected with Epichlo? elymi, were examined in natural populations and two common garden experiments using field-collected host tillers and seed progeny of maternal plants with known infection phenotypes. Transmission mode exhibited year-to-year variation in field and common garden environments. In the common garden there were consistent differences among maternal plant families in stroma production and significant correlations between stroma production in the common garden and in natural populations. Transmission mode differed among maternal families, spanning a continuum from pure vertical transmission to a high proportion of stroma production and horizontal transmission potential. Vertical transmission to seeds occurred at high rates in all maternal families regardless of their stroma production. Observed patterns of variation indicate that endophyte transmission mode and correlated changes in virulence can respond to selection by biotic and abiotic factors.     

不同胁迫处理对刺栲叶片叶绿素a荧光的影响

探讨了光强、温度和水分胁迫对刺栲(Castanopsis hystrix)体叶片叶绿素a荧光特征的影响,由此了解它的基本生物学特性。结果表明:(1)强光(1 300μmol.m-2.s-1左右)未胁迫时下降6.1%,表现轻微光抑制;(2)黑暗下低温(4℃,72 h)处理后电子传递速率下降较少(21.1%),初始荧光Fo保持稳定;与25℃对照相比,Fv/Fo和Fv/Fm无显著变化,表明黑暗下零上低温对PSⅡ潜在活性及光化学效率影响较小;(3)高温(40℃)胁迫显著影响了PSⅡ反应中心活性,ETR,Fv/Fm和Fv/Fo下降在处理2 h后达到极显著水平(p<0.01),Fo上升在处理4 h后也达到显著水平(p<0.05);(4)PEG诱导的水分胁迫严重影响了其光合机构活性,表现在无论与处理前比较、还是与耐旱种降真香(Acronychia pedunculata)的比较,其Fo上升和Fv/Fm、Fv/Fo下降都达到显著水平,表明其不耐干旱。     

Polyphenic wax production in Abacarus hystrix(Acari: Eriophyidae), and implications for migratory fitness

Abstract. . Wax production in the grass-feeding eriophyid Abacarus hystrix (Nalepa) is seasonally variable; enlarged lateral and dorsal bands of wax filaments develop in adults of summer generations. Wax filaments increase the total surface area of summer-generation mites, without a concomitant increase in cuticular surface-to-volume ratio. Genetic and environmental interactions in changes in the rate of wax production were examined. High temperatures, but not changes in photoperiod, were found to stimulate increased rates of wax production. The degree of wax filamentation was independent of the genetic origin of mites, hence filaments are polyphenic, rather than polymorphic, in origin. The role of wax filaments in the regulation of water-loss and in drag maximization were experimentally investigated. The relative survival of waxed and unwaxed mites was compared at various temperature and humidity combinations, and the influence of wax filaments on surface drag was assessed by comparing the slopes of regression lines of cuticular surface area relative to terminal velocity of waxed and unwaxed mites. Significantly greater survival times in waxed compared to unwaxed mites at low relative humidities suggest mat wax filaments have a function in the regulation of water-loss. Significantly lower mean terminal velocities in waxed mites indicated that total drag relative to cuticular surface area was greater in waxed than unwaxed mites, probably as a result of increased skin friction generated by wax filaments. The increased non-cuticular surface area created by wax filaments may be advantageous during summer-migrations of A.hystrix by increasing wind shear stress on the mites at the leaf margin, enhancing buoyancy while air-borne and reducing the rate of desiccation-induced mortality.     

中国刺栲林的分类与分布初探

介绍了中国刺栲林的群落生态学特性及其分布特征等,根据刺栲在群落中的地位(优势种、共建种、伴生种或偶见种),将刺栲林分为三种主要的群落类型,每一大类中,又依据分布地的环境状况等,各分为几种不同的亚型。值得注意的是,在以刺栲为优势种的群落类型中,随着海拔的升高,其共建种表现出独特的替代规律。同时,进一步探讨了刺栲群落形成与维持机制,认为在刺栲自身生物学和生态学特性的基础上,生境异质性和环境及人为干扰导致刺栲形成了不同群落类型,但其内在机制的揭示还需进行深入的研究。最后,对其速生丰产林和混交林营造提出了一些建议。     

Oviposition preference of swallowtail butterfly,Papilio polytes (Lepidoptera: Papilionidae) on four Rutaceae (Sapindales) host plant species

Abstract Oviposition preference and egg deposition site selection by the butterfly, Papilio polytes L. (Lepidoptera: Papilionidae) on four rutaceous host plants, Citrus aurantofolia (Christm.) Swing., Citrus hystrix DC., Citrus reticulata Blanco, and Murraya koenigii (L.) Sprengel, were assessed in field cages measuring 2 × 2 × 2 m. Simultaneous two-choice and four-choice oviposition tests of whole host plants were conducted. The mean total number of eggs laid per plant on C. reticulata in the two-choice test was significantly higher (P < 0.01) than those on C. aurantifolia, C. hystrix, and M. koenigii. Among the three other host plants, C. aurantifolia was preferred over C. hystrix, and M. koenigii (P < 0.01) and C. hystrix was preferred over M. koenigii (P < 0.01). In the four-choice test, C. reticulata was highly preferred and significantly different from C. hystrix and M. koenigii. However, no oviposition preference was detected with C. aurantifolia. Among the various plant parts in the two- and four-choice tests, eggs on leaves of each plant were the highest, followed by numbers on stems, and negligible numbers on pots. These numbers on leaves of C. reticulata and C. aurantifolia were not significantly different (P > 0.05), but differed significantly (P < 0.01) from those on leaves of C. hystrix and M. koenigii. The quantitative trend of egg-laying on stems was very similar to that observed for the leaves. Papilio polytes showed strong preference to lay eggs on the underside of leaves of all host plants than on the upper side or on the petiole. More eggs were laid on the upper side of each host plant than on its petiole. The four host plants in descending order of preference were C. reticulata≥C. aurantifolia > C. hystrix > M. koenigii. Although M. koenigii was the least preferred, it has the potential to serve as an alternative host plant for P. polytes which can be manipulated when necessary, to alleviate the infestation of this pest to the citrus industry.