Biological activities of extracts from traditionally used Nigerian plants against the European corn borer, Ostrinia nubilalis

Preliminary investigations with ethanolic (EtOH) extracts from five Nigerian plants show that extracts of Piper guineense Schum and Thonn (Piperaceae), Cedrela odorata L. (Meliaceae), Dennettia tripetala G. Baker (Annonaceae) and Aframomum melegueta (Rosch) K. Schum (Zingiberaceae) in artificial diets significantly reduced larval growth of European corn borer (ECB), Ostrinia nubilalis Hubner, at a concentration of 1000 ppm (0.1%). An extract of Xylopia aethiopica (Dunal) A. Rich (Annonaceae) was ineffective. When the extracts were subsequently incorporated into artificial diets at 300 ppm and offered to neaonates, larval mortality increased in the order A. melegueta (13%), D. tripetala (13%), P. guineense (27%), and C. odorata (48%). Larval and adult emergence periods increased with increasing concentration of P. guineense, C. odorata and D. tripetala indicating a toxic response. Nutritional indices for habituated third instar larvae with the two most promising plant extracts, P. guineense and C. odorata, showed that the efficiencies of conversion of digested food (ECD) was significantly reduced at 300 ppm suggesting a postdigestive toxicity of the extracts. P. guineense and C. odorata extracts show the best potential for development as botanical insecticides.     

Host-plant relationships of lycaenid butterflies: large-scale patterns, interactions with plant chemistry, and mutualism with ants

The Lycaenidae are the second-largest family of butterflies. From host-plant data collated for more than 1200 species worldwide, large-scale taxonomic, geographical and ecological patterns emerge which suggest that phytochemical similarities and barriers, coupled with phylogenetic conservatism and constraints are key factors governing hostplant use. More than two thirds of the lycaenid species are restricted to one plant family or genus. Affiliations with toxic plants are rare in the Lycaenidae, and excretion rather than sequestration of plant toxins appears to be their usual way of detoxifying host-plant compounds. Flavonoids are frequently sequestered by lycaenid larvae and are subsequently concentrated as pigments in the adults' wings, where they might play a role in visual communication. Mutualistic associations with ants occur in the larvae of more than 50% of the extant Lycaenidae species. Because of a conflict between the nutrient demands of the larvae and the proportion of plant-derived resources allocated to maintain the mutualism with ants, variation in resource quality often translates into variation of mutualistic capacities of the caterpillars, in particular under nutrient stress.     

An endochitinase gene expressed at high levels in the stylar transmitting tissue of tomatoes

A gene (pMON9617; Chi2;1) identified by screening a tomato pistil cDNA library has been found to encode a protein similar in sequence to class II chitinases. Using a baculovirus expression system we show that the Chi2;1 protein is an active endochitinase. The Chi2;1 protein is most similar in sequence to a previously described stylar chitinase (SK2) isolated from potato. Both proteins lack the diagnostic N-terminal cysteine-rich regions and the C-terminal vacuolar targeting signals of class I chitinases and appear to define a novel type of class II endochitinases associated with flowers. Chi2;1 is expressed predominantly in floral organs and its expression within these organs is temporally regulated. The highest level of expression is found in the transmitting tissue of the style where Chi2;1 mRNA begins to accumulate just prior to anthesis. In vegetative tissue, low levels of Chi2;1 mRNA were detected, and these levels did not increase in response to wounding or treatment with ethephon. mRNA from Chi2;1 orthologs was not detected in most other angiosperms tested, even including some members of the Solanaceae, and it is therefore unlikely that Chi2;1 is essential for stylar function. A fragment containing 1.4 kilobase pairs of 5-flanking DNA from the Chi2;1 gene was shown to drive high-level expression of an attached reporter gene in the styles of transgenic tomatoes. This fragment has utility for engineering expression of other coding regions in styles.     

Far-red enrichment and photosynthetically active radiation level influence leaf senescence in field-grown sunflower

Basal leaves frequently senesce before anthesis in high population density crops. This paper evaluates the hypothesis that quantitative and qualitative changes in the light environment associated with a high leaf area index (LAI) trigger leaf senescence in sunflower ( Helianthus annuus L.) canopies. Mean leaf duration (LD, time from achievement of maximum leaf area) of leaf 8 was significantly ( P < 0.05) reduced from 51 to 19 days as crop population density was increased from 0.47 to 4.76 plants m⁻². High compared to low plant population density was associated with earlier reduction in the photosynthetically active radiation (PAR) and red/far-red ratio (R/FR) reaching the target leaf. However the changes in R/FR preceded those in PAR. When the light environment of individual leaves of isolated plants growing under field conditions was manipulated using filters and FR-reflecting mirrors, LD was positively and linearly related with the mean daily PAR (MDR) received in the FR- (no FR enrichment) treatments. FR enrichment of light reaching the abaxial surface of the leaf significantly ( P < 0.05) reduced LD by 9 days at intermediate PAR levels with respect to FR-controls, but did not affect LD at the maximum PAR used in these experiments. However, when light reaching both leaf surfaces was enriched with FR, LD (for leaves receiving maximum PAR) was 13 days shorter than that of the FR- control. These results show that basal leaf senescence in sunflower is enhanced both by a decrease in PAR and by a decrease in R/FR.     

Effects of plant size on photosynthesis and water relations in the desert shrub Prosopis glandulosa (Fabaceae)

The Jornada del Muerto basin of the Chihuahuan Desert of southern New Mexico, USA, has undergone a marked transition of plant communities. Shrubs such as mesquite (Prosopis glandulosa) have greatly increased or now dominate in areas that were previously dominated by perennial grasses. The replacement of grasses by shrubs requires an establishment phase where small shrubs must compete directly with similar-sized grass plants. This is followed by a phase in which large, established shrubs sequester nutrients and water within their biomass and alter soil resources directly under their canopy, creating “islands” of fertility. We hypothesized that these two phases were associated with shrubs having different physiological response capacities related to their age or size and the resource structure of the environment. As a corollary, we hypothesized that responses of small shrubs would be more tightly coupled to variation in soil moisture availability compared to large shrubs. To test these hypotheses, we studied gas exchange and water relations of small (establishing) and large (established) shrubs growing in the Jornada del Muerto as a function of varying soil moisture during the season. The small shrubs had greater net assimilation, stomatal conductance, transpiration, and xylem water potential than large shrubs following high summer rainfall in July, and highest seasonal soil moisture at 0.3 m. High rates of carbon assimilation and water use would be an advantage for small shrubs competing with grasses when shallow soil moisture was plentiful. Large shrubs had greater net assimilation and water-use efficiency, and lower xylem water potential than small shrubs following a dry period in September, when soil moisture at 0.3 m was lowest. Low xylem water potentials and high water-use efficiency would allow large shrubs to continue acquiring and conserving water as soil moisture is depleted. Although the study provides evidence of differences in physiological responses of different-sized shrubs, there was not support for the hypothesis that small shrubs are more closely coupled to variation in soil moisture availability than large shrubs. Small shrubs may actually be less coupled to soil moisture than large shrubs, and thus avoid conditions when continued transpiration could not be matched by equivalent water uptake.     

使用MUG培养基定量检测植物药中大肠杆菌时荧光猝灭现象的发生与克服方法

实验中观察到,用ＭＵＧ培养基对植物药中的大肠杆菌定量时多发生荧光猝灭现象,影响检测结果。本文对此现象产生的原因与克服方法进行了系统的考察,发现以一种简便的转接方法可排除植物药介质对菌检的干扰。该方法由两组检验系列构成,当怀疑正常稀释系列（第一系列）４０ｈ培养液的荧光结果可能因猝灭现象呈假阴性时,立即分别将该系列的１—３号管培养液以０．５ｍｌ的接种量转接入新鲜的ＭＵＧ培养基（第二系列）,重新培养２４ｈ,荧光猝灭现象即可克服。综合两系列的荧光、产气和吲哚三项生化特征得出检品中大肠杆菌含量。实际应用表明,此法能显著提高使用该培养基时菌检结果的可靠性。     

A simple classification of the complex parts of vascular plants

Four operational morphological units are defined to characterize 'typical' stems, leaves, roots and hairS. Any complex part can be classified among these OMUs by a graphical representation or by a quadruplet suitable for computer-aided analyses. Thirty-nine examples are given, suggesting a continuous view of plant morphology.     

Analysis of DNA polymerase activity in Petunia protoplasts treated with clastogenic agents

Clastogenic agents, i.e. agents that can induce chromosome or DNA breakage, have been shown to enhance the rale of direct gene transfer to protoplasts. The effect was analysed at the enzymatic level using protoplast homogenates as well as intact protoplasts. For that purpose existing procedures were modified to enable measurement of DNA polymerase in vivo. In the system used, external DNA was able to enter the cells without the addition of membrane-permeabilizing compounds. When comparing total DNA polymerase activity of protoplasts irradiated with X-rays or UV-light with that of untreated cells we did not observe significant differences. Incubation of protoplasts with high doses of bleomycin affected total DNA polymerase activity negatively. but dideoxythymidine triphosphate-sensitive activity was not influenced. We conclude that the DNA strand-breaks induced by low doses of X-rays. UV-light or bleomycin do not increase the total or the repair-DNA polymerase activity and. therefore. that the increase in the transformation rates after DNA strand-breaking is not preceded by enhanced DNA polymerase activity.