Effects of Adjuvants on Entomopathogenic Nematode Persistence and Efficacy Against Plutella xylostella

The effects of spray additives on entomopathogenic nematode persistence and efficacy against Plutella xylostella (L . ) were studied . Several adjuvants were toxic to radish seedlings ( Raphanus sativus var . capitata L . ) but none was toxic to the nematodes or P. xylostella. In the laboratory , the adjuvants that provided the best antidesiccant activity based on a rank score were TX7719 , Rodspray oil and Nufilm P . Those providing less protection but better than the remaining adjuvants were 38 - F , dextrose and Pluronic F - 127 . In greenhouse trials , TX7719 and Rodspray oil were more effective than the other adjuvants tested . The stilbene brightener , Blankophor BBH , did not increase nematode efficacy consistently in greenhouse trials probably because the concentration used was too low . In field trials , the combination of TX7719 plus Blankophor BBH increased nematode persistence on watercress leaves ( Nasturium officinale R . Br . ) and efficacy against P. xylostella significantly . In vitro- pro duced nematodes benefited more from additives than in vivo- produced nematodes in the laboratory , but that difference was lost in the field . Overall , it was found that additives generally improved nematode persistence and efficacy , but the improvement was probably not sufficient to increase the feasibility of foliar applications of nematodes against P. xylostella. However , further evaluation of adjuvants is warranted for applications of nematodes to watercress for the control of P. xylostella.     

Manipulation of trait expression and pollination regime reveals the adaptive significance of spur length

Understanding the mechanisms of adaptive population differentiation requires that both the functional and adaptive significance of divergent traits are characterized in contrasting environments. Here, we (a) determined the effects of floral spur length on pollen removal and receipt using plants with artificial spurs representing the species-wide variation in length, and (b) quantified pollinator-mediated selection on spur length and three traits contributing to floral display in two populations each of the short-spurred and the long-spurred ecotype of the orchid Platanthera bifolia. Both pollen receipt and removal reached a maximum at 28–29 mm long spurs in a short-spurred population visited by short-tongued moths. In contrast, pollen receipt increased linearly across the tested range (4–52 mm) and pollen removal was unrelated to spur length in a long-spurred population predominantly visited by a long-tongued moth. The experimentally documented effects on pollen transfer were not reflected in pollinator-mediated selection through female fitness or pollen removal indicating that the natural within-population variation in spur length was insufficient to result in detectable variation in pollen limitation. Our study illustrates how combining trait manipulation with analysis of causes and strength of phenotypic selection can illuminate the functional and adaptive significance of trait expression when trait variation is limited.     

药用植物绶草(兰科)的菌根真菌群落组成分析

兰科菌根真菌(OMF)被认为是影响兰科植物物种丰度和分布的一个重要因素.对广域分布兰科植物的菌根区系进行研究有助于人们更深入地了解兰科植物分布格局的形成机制.本研究以我国广域分布的兰科药用植物绶草Spiranthes sinensis为材料,采用Illumina Miseq高通量测序技术对北京、上海、江西、广西、云南、...     

Population dynamics and comparative demographics in sympatric populations of the round-leaved orchids Platanthera macrophylla and P. orbiculata

Orchids (Orchidaceae) are a family of flowering plants with a high proportion of threatened taxa making them an important focus of plant conservation. Orchid conservation efforts are most effective when informed by reliable demographic research. We utilized transition matrix models to examine the population dynamics and demography within sympatric populations of a species pair of terrestrial round-leaved orchids, Platanthera macrophylla and P. orbiculata. The models were parameterized from a large data set spanning 9 years from field observations of over 1,000 orchids. Life table response experiments (LTRE) were used to identify which life history transitions, and which vital rates within those transitions, most contributed to observed differences between the two species and most contributed to interannual variation within each species. Results from mean transition matrices projected finite rates of population growth that were not significantly different between the two species, with P. macrophylla near the replacement rate and P. orbiculata below it. LTRE revealed that the difference in population growth rates between the two species was mostly due to differences in fecundity (flowering adult to protocorm transition) driven by differences in fruit set and seed germination into protocorm, which were much greater for P. macrophylla. The two primary contributors to interannual variation in population growth rates for both orchids were adult survival and fruit set, respectively. These findings indicate that any environmental disturbances harming adult survival or fecundity will have a disproportionately negative effect on the orchid populations.     

Floral induction and development in Phalaenopsis in vitro

Adventitious shoots formed from nodal sections of floral-stalks of Phalaenopsis Pink Leopard Petra that had been propagated on Hyponex medium with 6-benzyladenine (BA). After subculturing adventitious shoots on Vacin-Went medium with BA, more than 70% of the shoots formed floral buds, and 10% of the floral buds flowered in 9-month-old shoots. Floral buds were not formed on the adventitious shoots cultured on Vacin-Went medium lacking BA. A high concentration of total nitrogen inhibited the development of floral buds, and low-temperature treatments failed to induce the formation of floral buds in vitro.     

Gene flow and effective population size in Lepanthes (Orchidaceae): a case for genetic drift

Genetic drift can play an important role in population differentiation, particularly when effective population sizes are small and gene flow is limited. Such conditions are suspected to be common in the species-rich Orchidaceae. We investigated the likelihood of genetic drift in natural populations of three endemic species of Lepanthes (Orchidaceae) from Puerto Rico. We estimated effective population size, Ne, using three ecologically based methods. Two of the three estimates were based on variance in reproductive potential and the third was based on coalescence time. All estimates of Ne were usually <40% of the standing population size, resulting in values of <20 individuals per population. Based on starch gel electrophoresis of isozymes, Nm estimates suggest restricted gene flow among populations in the range of one or less successful migrant per generation. Genetic differentiation among populations is expected under such conditions from random genetic drift. Indeed we observed high genetic differentiation among populations (L. rubripetala, F_ST> G_ST, 6; θ.248, 0.266, 0.293; L. rupestris, 0.148, 0.169, 0.138; L. eltoroensis, 0.251, 0.219, 0.218, respectively). Genetic drift is likely to be important for population differentiation in Lepanthes as a result of small effective population sizes and restricted gene flow.     

Beetle pollination of Luisia teres (Orchidaceae) and implications of a geographic divergence in the pollination system

The epiphytic orchid Luisia teres on Okinawa Island, the Ryukyus, Japan, sexually attracts male Protaetia beetles for pollination through floral scent. Here, the pollination system of L. teres on the Satsuma Peninsula, Kyushu, located approximately 600 km north of Okinawa Island, is reported. The inconspicuous flowers depend on the Cetoniinae beetles Protaetia orientalis submarumorea and Pseudotorynorrhina japonica, which both usually feed on fermented sap/ripe fruits, for pollination. The flower-visiting P. orientalis submarumorea beetles included both males and females, and pseudocopulation was never observed. Pollinaria removal and pollination were achieved while beetles fed on floral nectar. Although P. orientalis submarumorea did not necessarily remove pollinaria more frequently than Ps. japonica, the pollinaria attached precisely to the central part of their clypeus, unlike on Ps. japonica. Our findings suggest that a geographic divergence in the pollination system occurs in Japanese L. teres. In the Ryukyus, the orchid adopts a specialized pollination system with only male-attractive olfactory stimuli, whereas in Kyushu it has a relatively more generalized system based on only a food reward.