A novel endoperoxide diterpene, 7α-hydroxy-abieta-8(14)-en-18-ol 9,13α-endoperoxide (compound 1), was isolated from the stems of Microtoena insuavis (Hance) Prain ex Dunn, along with 4,4''-dihydroxytruxillic acid (compound 2), gallic acid (compound 3), ellagic acid (compound 4), 3-O-methylellagic acid 3''-O-α-rhamnopyranoside (compound 5), 3''''''-O-methylcrenatoside (compound 6), crenatoside (compound 7), apigenin (compound 8), succinic acid (compound 9), β-sitosterol (compound 10), and β-daucosterol (compound 11). The structures of these compounds were elucidated on the basis of spectral evidence.(Author for correspondence.Tel (Fax): (0)28 8522 5401; E-mail: zhanggl@cib.ac.cn)

The developmental types of secretory cavities in Citrus remain controversial. The relationship between secretory cavity development and the accumulation of essential oil in fruits of Citrus species is also unknown. In order to develop better insights into these problems, histological, histochemical, and cytochemical methods were used to investigate secretory cavity development and the accumulation of essential oil at different developmental stages of fruits of Citrus medica L. var. sarcodactylis (Noot.) Swingle. The results indicate that the secretory cavity of the variety seemed to originate from an epidermal cell and a subepidermal cell. These two cells underwent successive divisions, resulting in the formation of two parts: (i) a conical cap; and (ii) a globular gland. The formation of the lumen was schizolysigenous. Regular changes in the size of vacuoles and the accumulation of essential oil were revealed during the process of secretory cavity development. In addition, when fruits were a light yellow or golden color, the structure of secretory cavities was well developed and the content of essential oil in a single fruit reached a maximum. It would be most appropriate to collect the fruit as a medicinal material at this time.(Author for correspondence.Tel: (0)20 8528 8393; Fax: (0)20 8528 2180; E-mail:wh@scau.edu.cn)

nifB– MoFe protein (nifB–Av1), ΔnifE MoFe protein (ΔnifE Av1) and ΔnifZ MoFe protein ΔnifZ Av1) were obtained by chromatography on DE52, Sephacryl S-300 and Q-Sepharose columns from nifB point-mutated, nifE deleted and nifZ deleted mutant stains (UW45, DJ35 and DJ194) of Azotobacter vinelandii Lipmann, respectively. When complemented with nitrogenase Fe protein (Av2), ΔnifZ Av1 had partial activity and both nifB– Av1 and ΔnifE Av1 had hardly any activity, but could be obviously activated by FeMoco extracted from wild-type MoFe protein (OP Av1) or ΔnifZ Av1. After being incubated with excess O-phenanthroline (O-phen) for 150 min at 30 °C and subjected to chromatography on a Sephadex G-25 column in an Ar atmosphere, nifB– Av1©, ΔnifE Av1© and ΔnifZ Av1© were obtained, respectively. Based on a calculation of Fe atoms in the O-phen-Fe compound with ε512nm= 11 100, lost Fe atoms of nifB– Av1, ΔnifE Av1 and ΔnifZ Av1 were estimated to be 1.35, 2.89 and 8.44 per molecule of protein, respectively. As a result of the Fe loss, ΔnifZ Av1 loses its original activity. In the presence of both MgATP and Av2, these Fe-losing proteins, but not the original proteins untreated with O-phen, could be significantly activated by reconstituent solution (RS) composed of dithiothreitol, ferric homocitrate, Na2S and Na2MoO4, or K2CrO4, or KMnO4. But in the absence of MgATP or Av2, the activation did not occur, with the exception that ΔnifZ Av1© was partially activated, and the activity was only 17%. These findings indicate that: (i) ΔnifZ Av1 with half P-cluster content is somewhat different from FeMoco-deficient nifB– Av1 and ΔnifE Av1 with respect to protein conformation either before or after treatment with O-phen; (ii) full activation of these proteins with RS requires pretreatment with O-phen and the simultaneous presence of MgATP and Av2.(Author for correspondence.Tel: (0)10 6283 6219; Fax: (0)10 6259 0833; E-mail:jfhuang@ibcas.ac.cn)

The growth characteristics, different physiological parameters, photosynthetic activity (14CO2 fixation), and the translocation rate of photoassimilates in different taro (Colocasia esculenta L. Schott) genotypes was studied in order to determine the possible use of these parameters as selection criteria for different widely used genotypes of taro (Delta No. 9, 15, 20, 21, and balady). The results obtained suggest that Delta No. 21 shows the most significant increase in all parameters tested compared with the control (balady), followed by Delta No. 9, 15, and 20, respectively. The results show a positive correlation between photosynthetic activity, translocation efficiency, and total yield. The selected clone Delta No. 21 is recommended for cultivation in the delta region of Egypt.(Author for correspondence.Tel: +20 2337 0588; Fax: +20 2337 1082; E-mail:helal_moussa@hotmail.com)

In the present study, the relationship between the nutritional status of leaves and the development of symptoms of cotton leaf curl virus (CLCuV) in two cotton (Gossypium hirsutum L.) cultivars (i.e. CIM-240 and S-12) was investigated. The incidence of disease attack was found to be 100% in the S-12 cultivar and 16% in the CIM-240 cultivar. Geminivirus particles in infected leaves were confirmed by transmission electron microscope examination of highly specific geminivirus coat protein antisera-treated cell sap. The CLCuV impaired the accumulation of different nutrients in both cultivars. A marked decrease in the accumulation of Ca2+ and K+ was observed in infected leaves. However, the disease had no effect on leaf concentrations of Na+, N, and P. It was observed that the curling of leaf margins in CLCuV-infected plants was associated with the leaf Ca2+ content; leaf curling was severe in plants with a significant reduction in Ca2+ content. Moreover, leaf K+ content was found to be associated with resistance/susceptibility to CLCuV infection.(Author for correspondence.Tel: +92 41 265 2666; Fax: +92 41 265 4213; E-mail: niabmyashraf@yahoo.co.uk)

In the present study, we investigated the induction of volatile organic compounds (VOCs) of Lycopersicon esculentum Mill. and its resistance to Botrytis cinerea Pers. by burdock oligosaccharide. The disease severity of L. esculentum was evaluated 48 h after treatment with 0.6% burdock oligosaccharide, followed by inoculation with a spore suspension of B. cinerea. The formation of O2-., the activity of lipoxygenases (LOX), peroxidase (POD), catalase (CAT), and superoxide dismutase (SOD), and the quantity and quality of changes in VOCs were determined a period of time after treatment with 0.6% burdock oligosaccharide. The results demonstrated that the disease index in treated plants was decreased by 42.5% compared with control 96 h after inoculation. The production of O2-. reached a maximum 6 h after treatment (1.36-fold compared with control). There was an increase in LOX, POD, CAT and SOD activity in response to burdock oligosaccharide treatment and the enzymes showed different trends in the time-course of induction. At 120 h after treatment, (E)-2-hexenal was increased by 92% compared with control, whereas methyl salicylate showed a gradual increase with induction period. Previous results had demonstrated that chitosan elicitor enhanced the production VOCs of L. esculentum and decreased plant susceptibility towards B. cinerea. Together, these findings suggest that increasing the production of VOCs in response to burrdock oligosaccharide may be an important mechanism for L. esculentumin its defense against pathogens. In addition, burrdock oligosaccharide may act as a potent elicitor of resistance to disease in L. esculentum.(Author for correspondence.Tel: +86 (0)532 8896 7422; Fax: +86 (0)532 8896 9292; E-mail: ksc313@126.com)

The present experiment, involving both the in vivo injection of abscisic acid (ABA) into apple (Malus domestica Brohk.) fruits and the in vivo incubation of fruit tissues in ABA-containing medium, revealed that ABA activates both soluble and cell wall-bound acid invertases. Immunoblotting and enzyme-linked immunosorbent assays showed that this ABA-induced acid invertase activation is independent of the amount of enzyme present. The acid invertase activation induced by ABA is dependent on medium pH, time course, ABA dose, living tissue and developmental stage. Two isomers of cis-(+)-ABA, (–)-ABA and trans-ABA, had no effect on acid invertases, showing that ABA-induced acid invertase activation is specific to physiologically active cis-(+)ABA. Protein kinase inhibitors K252a and H7 as well as acid phosphatase increased the ABA-induced effects. These data indicate that ABA specifically activates both soluble and cell wall-bound acid invertases by a posttranslational mechanism probably involving reversible protein phosphorylation, and this may be one of the mechanisms by which ABA is involved in regulating fruit development.(Author for correspondence.Tel：010-62732784；Fax：010-62731899；E-mail：zhangdp@sohu.net)

Biomass accumulation, leaf longevity and growth rate of two spring forest geophytes, Scilla bifolia L. and Arum maculatum L. were estimated separately for three size groups within each population of these species. Despite the differences in leaf longevity, both species showed a similar pattern of biomass accumulation in relation to their phenologies and reproductive demands. Eco-physiological acclimation to changing light environment was assumed through photosynthetic parameters and dynamics of leaf area index in the predominant size group of each species. A light response curve was measured under natural light for each species through the continuum of its phenology to quantify the photosynthetic photon flux density at light saturation, light-saturated photosynthetic rate, light compensation point, and dark respiration. Light-saturated assimilation per leaf area basis, dark respiration rate and light compensation points were significantly higher in S. bifolia relative to A. maculatum. However, the acclimation of photosynthesis that would respond to light changes in environment was not found in S. bifolia. In contrast, in A. maculatum a marked shift in the light dependence of photosynthesis through the season was noticed, which resulted in a strong photosynthetic acclimation to the low-light conditions. Accompanied by significant leaf area index, this efficient low-light photosynthesis enabled greater leaf longevity, and consequently longer accumulative period to A. maculatum. From the different parameters that we determined (both photosynthetic acclimation and growth strategy) it would appear that these species belong to two distinct subgroups: S. bifolia to the early and A. maculatum to the late vernals.(Author for correspondence.Tel: +381 11 207 8360; Fax: +381 11 276 1433; E-mail:zoricaj@ibiss.bg.ac.yu)

Plants growing on both sides of the Tarim River in western China serve as a natural barrier containing the deserts and protecting the oasis, and their growth is greatly affected by water conditions in their local habitat. We studied the physiological responses of three different types plants (i.e. Populus euphratica Oliver, Tamarix ramosissima L., and Apocynum venetumas Linn) to changing groundwater levels by analyzing changes in chlorophyll, soluble sugar, proline (Pro), malondialdehyde (MDA), superoxide dismutase (SOD), peroxidase (POD), indoleacetic acid (IAA), giberellic acid, abscisic acid (ABA) and cytokinin (CK). Relationships between these physiological characteristics and groundwater levels were analyzed in order to assess the drought tolerance of the three plant species based on the values of average membership function. We found that MDA, SOD and ABA were more susceptible to changes in groundwater level, followed by POD, IAA and CK. Among the three plant species, Populus euphratica responded physiologically less to changing groundwater level than T. ramosissima and A. venetumas.(Author for correspondence.Tel. +86 (0)991 7885432; E-mail:chenyn@ms.xjb.ac.cn)

Comparisons between competing and non-competing sunflower (Helianthus annuus L.) populations demonstrate pronounced effects of density on plant height growth, height-to-crown width ratio, and a population’s height inequality. In the present study, non-destructive measurements of height and the projected crown area of sunflower plants were taken at seven times from emergence to fruit maturation in even-aged monospecific stands with initial densities of 1, 4, 16, and 64 plants/m2. The mean height of populations increased and then decreased with increasing population density; the height inequalities of uncrowded populations decreased during stand growth, whereas the height inequalities of crowded populations decreased first and then increased during stand development. The interindividual relationships between the relative height growth rate and height within uncrowded populations became significantly negative during population growth, whereas these relationships were negative first and then became positive during the development of crowded populations. In the uncrowded populations, the static interindividual relationship between height-to-crown width ratio and volume was positive, whereas for the crowded population these relationships became negative with increasing competition for light. The data suggest that the plastic responses of plant height and height-to-crown width ratio to light competition will become more intense with increasing competition intensity. The results of the present study argue strongly for the importance of size-dependent individual-level plastic responses due to size-asymmetric light competition in generating the variations in population height inequality.(Author for correspondence.Tel:0931-8912849；Fax:0931-8912823； Email：wangg@lzu.edu.cn)

After converting cropland to forest, carbon is sequestered in the aggrading biomass of the new forests, but the question remains, to what extent will the former arable soil contribute as a sink for CO2? Quantifying changes in soil carbon is an important consideration in the large-scale conversion of cropland to forest. Extensive field studies were undertaken to identify a number of suitable sites for comparison of soil properties under pasture and forest. The present paper describes results from a study of the effects of first rotation larch on soil carbon in seven stands in an afforestation chronosequence compared with adjacent Korean pine, pasture, and cropland. An adjacent 250-year-old natural forest was included to give information on the possible long-term changes in soil carbon in northeast China in 2004. Soil carbon initially decreased during the first 12 yr before a gradual recovery and accumulation of soil carbon occurred. The initial (0–12 yr) decrease in soil carbon was an average 1.2% per year among case studies, whereas the increase in soil carbon (12–33 yr) was 1.90% per year. Together with the carbon sequestration of forest floors, this led to total soil carbon stores of approximately 101.83 Mg/hm2 over the 33-year chronosequence. Within the relatively short time span, carbon sequestration occurred mainly in tree biomass, whereas soil carbon stores were clearly higher in the 250-year-old plantation (184 Mg/hm2). The ongoing redistribution of mineral soil carbon in the young stands and the higher soil carbon contents in the 250-year-old afforested stand suggest that nutrient-rich afforestation soils may become greater sinks for carbon (C) in the long term.(Author for correspondence.Tel: +86 (0)10 6488 9697; Fax: +86 (0)10 6485 1844; E-mail:ohua@igsnrr.ac.cn)

The localization of 18S ribosomal RNA genes (rDNA) by fluorescence in situ hybridization (FISH) had been performed for some species of Paeonia. However, the pattern of 18S rDNA loci among populations is indistinct. In the present study, we localized 18S rDNA loci on meiotic or mitotic chromosomes of six populations of Paeonia obovata Maxim. (Paeoniaceae). Different numbers of rDNA loci were found with different diploid (2n=10) populations, namely eight (Lushi and Mt. Jiuhua populations), 10 (Mt. Taibai population), and seven (Mt. Guandi population), whereas tetraploid (2n=20) populations were all found with 16 loci. All rDNA loci were mapped near telomeres of mitotic chromosomes and there was no chromosome with two loci. The present results show that molecular cytological polymorphism exists among P. obovata diploid populations, indicating that structural variations occurred frequently during the evolutionary history of this species, accompanied with differentiation among populations.(Author for correspondence.Tel: (0)10 6283 6492; Fax: (0)10 6259 0843; E-mail:zhangdm@ibcas.ac.cn)