Relative effects of nocturnal vs diurnal pollinators and distance on gene flow in small Silene alba populations

Silene alba exists in natural metapopulations throughout its range and is visited by a suite of both diurnal and nocturnal pollinators. Pollen-mediated gene flow may help reduce genetic isolation of subpopulations. Here, we compared the relative effects of nocturnal vs diurnal pollinators on pollen-mediated gene flow in subpopulations separated by two distance treatments. We established populations consisting of genetically marked individuals in an old field in Tennessee (USA). Electrophoretic examination of seedlings produced by plants exposed to nocturnal, diurnal and control pollinator treatments and separated by either 20 or 80 m allowed us to directly measure pollen-mediated gene flow. Gene flow was more common between populations separated by only 20 m. Nocturnal pollinators were responsible for most gene flow between populations, regardless of distance. Diurnal pollinators played only a small role in pollen-mediated gene flow. The results suggest that nocturnal pollinators are better than diurnal pollinators at moving pollen between small S. alba subpopulations. However, their effectiveness declines as the distance between subpopulations increases, making them relatively ineffective at moving genes between isolated subpopulations.     

桑叶抑菌效果的探讨

采用一系列真菌和细菌,试验了桑叶汁的抑制作用,结果表明,桑叶汁对大数G^ 和G^－氏细菌以及部分酵母菌的生长具较强的抑制作用,且具有热稳定性强,抑菌浓度低,抑菌PH范围广的特点,对霉菌无抑制作用。     

The role of glucosinolates and their hydrolysis products in oviposition and host-plant finding by cabbage webworm, Hellula undalis

The cabbage webworm, Hellula undalis (Fabricius) (Lepidoptera: Pyralidae), a tropical pest on crucifers (Brassicaceae), differentiated among host‐plant species for oviposition in laboratory and field tests. White mustard, Sinapis alba (L.) var. Selinda, was the preferred host‐plant, followed by Brassica juncea (L.) Czern. et. Coss var. Canadian brown mustard, and pak‐choi, Brassica campestris L. ssp. chinensis var. Joi Choi, Black Behi and Bai Tsai. Glucosinolates (GS), secondary plant compounds characteristic to the Cruciferae plant family, and their breakdown products were analyzed by using HPLC and GC‐MS‐techniques. Species differed in GS composition and concentration. Content of GS was highest in S. alba with progressively lower contents detected in B. juncea and B. chinensis. The aromatic GS, 4‐hydroxybenzyl‐GS and benzyl‐GS, were detected in S. alba. In B. juncea the alkenyl GS, allyl‐GS, dominated, whereas in varieties of B. chinensis indolyl and alkenyl GS predominated. Oviposition of H. undalis females on the non‐host‐plant Vigna unguiculata ssp. sesquipedalis (L.) Fruwirth was stimulated by application of GS extracts from the crucifer species; the extract from S. alba was preferred, followed by extracts from B. juncea and B. chinensis. Hydrolysis of GS in the plant extract from B. chinensis causes loss of the oviposition stimulatory effect of the extract. Application of the GS, allyl‐GS, and benzyl‐GS also stimulated oviposition by H. undalis. Significantly more eggs were laid on leaves treated with the aromatic GS, benzyl‐GS, than with the alkenyl GS, allyl‐GS. Host‐plant odor attracted H. undalis females but not males, in behavioral assays conducted in a Y‐tube olfactometer. Low concentrations of the GS hydrolysis product, allyl‐isothiocyanate, induced anemotaxis of females, but a high concentration of allyl‐isothiocyanate was repellent. Oviposition by H. undalis females was not stimulated by host‐plant volatiles. Females laid eggs on inserted traps and the walls of the Y‐tube regardless of presence or absence of host‐plant odor. The relevance of these results in the context of crucifer‐insect interactions is discussed.     

白花刺参中两个新三萜皂甙

从著名藏药白花刺参（Morina nepalensis var.alba Hand.-Mazz)的水溶性部分分离到2个新三萜皂甙-刺参甙K（1）和刺参甙L（2）,以及一个已知三萜皂甙mazusaponinⅠ（3)。应用波谱和化学方法,刺参甙K和刺参甙L的结构分别鉴定为3-O-α-L-arabinopyranosyl-（1→）-β-D-xylopyranosyl siaresinolic acid(1)和3-O-β-D-glucopyranosyl-(1→3)-α-L-arabinopyranosyl siaresinolic acid28-O-β-D-glucopyranosyl-(1→6)-β-D-glucopyranoside(2)。     

Histology of the interactions of Paecilomyces lilacinus with Meloidogyne incognita on Eclipta alba (L.)

Abstract

Under greenhouse conditions, the experiment was conducted to test the efficacy of opportunistic and nematophagous hyphomycete, Paecilomyces lilacinus against root-knot nematode, Meloidogyne incognita on Eclipta alba. The treatment comprised inoculation of E. alba with M. incognita alone (N) and in combination with P. lilacinus (one week before (T₁), simultaneously (T₂), one week after (T₃), two weeks after (T₄) and three weeks after (T₅)). The results showed that the application of P. lilacinus before one week of nematode inoculation (T_l) was more effective than other treatments. A significant enhancement was noticed in the growth and yield of E. alba. Root-knot and egg mass indices were suppressed due to destruction of the mature females and the egg masses. Histopathological studies revealed the presence of P. lilacinus hyphae in and around the females and the eggs.     

Temporal and spatial patterns in fire occurrence during the establishment of mixed‐oak forests in eastern North America

Question: What was the role of fire during the establishment of the current overstory (ca. 1870–1940) in mixed‐oak forests of eastern North America? Location: Nine sites representing a 240‐km latitudinal gradient on the Allegheny and Cumberland Plateaus of eastern North America. Methods: Basal cross‐sections were collected from 225 trees. Samples were surfaced, and fire scars were dated. Fire history diagrams were constructed and fire return intervals were calculated for each site. Geographic patterns of fire occurrence, and fire‐climate relationships were assessed. Results: Fire was a frequent and widespread occurrence during the formation of mixed‐oak forests, which initiated after large‐scale land clearing in the region ca. 1870. Fire return ranged from 1.7 to 11.1 years during a period of frequent burning from 1875 to 1936. Fires were widespread during this period, sometimes occurring across the study region in the same year. Fires occurred in a variety of climate conditions, including both drought and non‐drought years. Fires were rare from 1936 to the present. Conclusions: A variety of fire regime characteristics were discerned. First, a period of frequent fire lasted approximately 60 years during the establishment of the current oak overstory. Second, fire occurred during a variety of climate conditions, including wet climates and extreme drought. Finally, there was within‐site temporal variability in fire occurrence. These reference conditions could be mimicked in ongoing oak restoration activities, improving the likelihood of restoration success.     

Effects of optimum doses of nitrogen,phosphorus, potassium and calcium on silkworm,Bombyx mori L., growth and yield

Silkworm rearing has been an income source for small-holding farmers in Pakistan. Over the years efforts have been made to improve silkworm quality and quantity and thus develop better prospects for increasing yield and income. Mulberry leaves Morus alba L. in a series of experiments have been supplemented with various nutrients in different doses and combinations. Relative success has been achieved in this context. In our present experiments on silkworm Bombyx mori L., we fed the larvae on mulberry leaves supplemented with different doses of N (0.2%), P (0.1%), K (0.3%) and Ca (0.1%) at 26 ± 3°C with 65 ± 5% relative humidity. The results showed better outputs in terms of food consumption (72.55 g/10 larvae), coefficient of utilization (76.45%), body weight (70.07 g/10 larvae) and body length (8.56 cm/larvae) than where simple mulberry leaves were offered. Our net gains with these production parameters have been in terms of heavier cocoons with and without pupa (2.25 and 0.69 g/cocoon), respectively.     

Morpho‐anatomical and physiological differences between sun and shade leaves in Abies alba Mill. (Pinaceae,Coniferales): a combined approach

Morphology, anatomy and physiology of sun and shade leaves of Abies alba were investigated and major differences were identified, such as sun leaves being larger, containing a hypodermis and palisade parenchyma as well as possessing more stomata, while shade leaves exhibit a distinct leaf dimorphism. The large size of sun leaves and their arrangement crowded on the upper side of a plagiotropic shoot leads to self‐shading which is explainable as protection from high solar radiation and to reduce the transpiration via the lamina. Sun leaves furthermore contain a higher xanthophyll cycle pigment amount and Non‐Photochemical Quenching (NPQ) capacity, a lower amount of chlorophyll b and a total lower chlorophyll amount per leaf, as well as an increased electron transport rate and an increased photosynthesis light saturation intensity. However, sun leaves switch on their NPQ capacity at rather low light intensities, as exemplified by several parameters newly measured for conifers. Our holistic approach extends previous findings about sun and shade leaves in conifers and demonstrates that both leaf types of A. alba show structural and physiological remarkable similarities to their respective counterparts in angiosperms, but also possess unique characteristics allowing them to cope efficiently with their environmental constraints.     

The role of glycine in determining the rate of glutathione synthesis in poplar. Possible implications for glutathione production during stress

The terminal step of glutathione (GSH) synthesis is the condensation of γ-glutamyl-cysteine (γ-EC) with glycine. Relatively little information exists concerning the importance of photorespiratory glycine in determining the rate of conversion of γ-EC to GSH. Consequently, the effect of exogenous glycine and of illumination on foliar contents of γ-EC and GSH was studied in excised leaves and leaf discs from untransformed poplar ( Populus tremula × P. alba ) and poplar overexpressing γ-glutamylcysteine synthetase (γ-ECS; EC 6.3.2.2). Poplars strongly overexpressing γ-ECS (ggs28) had enhanced levels of γ-EC and GSH compared to untransformed poplars. The relationship between γ-EC and GSH contents in ggs28 was light dependent. In illuminated leaves, GSH contents were up to 50-fold higher than γ-EC. On darkening, γ-EC accumulated markedly and GSH declined, so that the GSH:γ-EC ratio was close to 1. These dark-induced changes were prevented by supplying glycine through the petiole or by incubation of leaf discs on glycine. Dark accumulation of γ-EC in leaf discs from untransformed poplar was also prevented by supplying glycine. Supplying cysteine in the dark to discs from untransformed poplar and ggs28 increased γ-EC levels markedly but GSH levels only slightly. Subsequent illumination caused γ-EC to decrease and GSH to increase. Supplying glycine in concert with cysteine had similar effects to illumination. The data suggest that photorespiratory glycine is essential for GSH synthesis, especially under stress conditions, where increased amounts of GSH are required.