Impact of Seasonal Fluctuations on the Sediment-Mercury, its Accumulation and Partitioning in Halimione portulacoides and Juncus maritimus Collected from Ria de Aveiro Coastal Lagoon (Portugal)

The availability of metals to plants is a complex function of numerous environmental factors. Many of these factors are interrelated, and vary seasonally and temporally. The current study intended to understand the influence of seasonal fluctuations and the vegetation of salt marsh plants (SMPs; Halimione portulacoides, Juncus maritimus) on sediment??s mercury (Hg) and its pH and redox potential (Eh), as well as their cumulative effect on the plant??s Hg-accumulation and Hg-partitioning potential. The area selected for the study was Laranjo Basin at Ria de Aveiro lagoon (Portugal) where a known Hg gradient was existed due to chlor-alkali plant discharge. Three sampling sites (L1, L2 and L3) were selected along a transect defined by the distance from the main Hg source. Samples were also collected from the Hg-free site (R). Irrespective of the plant vegetation, Hg in sediments gradually increased with a decreasing distance towards Hg-point source. The sediment colonised by J. maritimus showed more Hg concentration compared with H. portulacoides irrespective of the season. As a whole, J. maritimus accumulated Hg more than H. portulacoides at all the sampling sites, whereas in root, stem and leaf, the concentration was ranked as: L1 > L2 > L3 in both the plant species and was differentially influenced by seasonal changes. Moreover, root of both plants exhibited highest Hg concentration compared with stem and leaf. In addition, the leaf of H. portulacoides exhibited more Hg than leaves of J. maritimus. Bioaccumulation and translocation factors and dry weight were differentially influenced by seasonal changes. Taking together the results, the physico-chemical properties of sediment especially the sediment-Eh seems to be influnced by the type of plant vegetation and seasonal changes which in turn may have influenced the chemistry of sediments; thus, it enfluences the bioavalability of Hg and the Hg-retention capacity of both salt marsh sediments (SMSs) and SMPs (bioaccumulation factor). Moreover, SMSs vegetated by J. maritimus exhibited a stronger capacity for the retention and phytostabilization of Hg belowground (in sediments and/or roots) than those dominated by H. portulacoides. Conversely, those SMSs extensively vegetated by H. portulacoides are expected to translocate more Hg to aboveground parts, acting as a potential source of this metal to the marsh ecosystem. Therefore, J. maritimus and H. portulacoides may be used repectively for phytostabilization (in rhizosediments) and phytoextraction (by accumulation in aboveground plant tissue for subsequent plant removal).     

Nitrogen source‐sink relationship in cotton

Although attempts have been made in developing soil and plant analysis procedures for cotton (Goseipium hirsutum) , N nutrition is not completely understood. To the present it has not been possible to predict when the maximum N utilization efficiency could be achieved. By exposing cotton plants to a ¹⁵N enriched solution for 5 periods of 30 days each in a temperature controled greenhouse, the accumulation and redistribution of N within the plant was followed in order to define the main N sources and sinks for each period. The main N source within the cotton plant after the first square stage was the leaves. Stems and burs acted as temporary storage organs remobilizing N to the seeds late in the growing season, while the roots were fairly neutral. Dry matter accumulation during the reproductive stage was not related to N redistribution in the plant, except for bolls. So at this stage, dry matter accumulation was not a important component in the N source‐sink relationship within the cotton plant.     

Growth and light receipt by mainstem cotton leaves in relation to plant density in the field

The expansion of individual mainstem cotton leaves and light receipt at their natural angle of display were measured in the field to determine simple expressions for growth and light interception of cotton leaves. Plant density and planting date were varied in three seasons to generate a range of leaf and plant sizes.When expressed in thermal time, leaves appeared regularly at intervals of 2.9 physiological days (or 41 day degrees) and the leaves expanded for a relatively constant time of 18 p-days (253 day degrees), being insensitive to plant density and planting date. Leaf size and, therefore, daily rate of leaf expansion were strongly influenced by position on the plant, plant density and planting date (largest leaves in the middle region of the plant, at low plant densities and late planting dates). These effects were consistent with leaf size at initiation and relative leaf expansion rate being influenced by assimilate competition within the plant either between leaves and fruiting branches, or due to mutual shading. Planting date effects were consistent with a temperature response.Leaves faced the sun in the early morning and late afternoon, which a simulation study suggested allowed an extra 40% photosynthesis at these times. However, since absolute light levels were low at these times, simulated daily photosynthesis was only increased by 9% over leaves which stayed at constant leaf display.Plant density highly influenced light extinction coefficients (K) for mainstem leaves when measured at their natural angle of display. For plant densities of 2, 8 and 24 m⁻² K was 3.56 ± 0.26, 1.76 ± 0.08 and 1.15 ± 0.10, respectively. These effects were attributed to the more “clumpy” nature of plants at low density. When measured at ground level with a linear sensor held horizontally under a medium plant density crop, K was 0.87 ± 0.03. Therefore, it was postulated that K for fruiting branch leaves might be substantially lower than for mainstem leaves. It was demonstrated that K could have a large effect on calculated photosynthesis of lower leaves in a crop model based at the single leaf level.     

Influence of elevated CO2 and mild water stress on nonstructural carbohydrates in field-grown cotton tissues

Root, stem and leaf tissues, from cotton plants exposed to CO₂ at ambient (370 μmol mol⁻¹ (control)) or elevated (550 μmol mol⁻¹ (FACE; free-air carbon dioxide enrichment)) levels in the field during the 1990 and 1991 growing seasons, were analyzed for nonstructural carbohydrates (glucose, fructose, sucrose and starch). Besides the FACE treatment, these plants were also exposed to two irrigation levels: 100% and 67% replacement of evapotranspiration. FACE had a greater effect upon cotton plant nonstructural carbohydrates than did irrigation treatments. Leaf carbohydrate content was increased by FACE, but this increase was much more pronounced in the stems and roots. Starch and soluble sugars in leaves in FACE plots tended to be consistently greater than in control leaves, without much change in carbohydrate content during the growing season. In contrast, root and stem, starch and soluble sugar pools were strongly increased by FACE and fluctuated strongly during the growing season. In both seasons, stem and taproot nonstructural carbohydrate content passed through a minimum during periods of heavy boll set. The fluctuations in stem and root carbohydrate content were therefore probably caused by the varying metabolic demands of the developing plant. These results suggest that a significant effect of CO₂ enrichment on starch-accumulating plants is an increase of nonstructural carbohydrate, especially starch, in nonleaf storage pools. This buildup occurs somewhat independently of the water status of the plant, and these enlarged pools can be drawn upon by the growing plant to maintain growth during periods of high metabolic demand.     

不同液体有机肥对新疆棉花生长及土壤养分的影响

为研究不同液体有机肥对新疆棉花生长及土壤养分的影响，进而确定滴灌棉田最适宜的液体有机肥类型，为优化新疆滴灌棉花施肥技术提供理论依据，采用盆栽试验，设置5个处理包括不施肥（CK）、常规施肥（化肥，CF）、含氨基酸液体有机肥（AF）、含腐殖酸液体有机肥（HF）、酸性有机肥浸提液（BF），考察了不同施肥处理对棉花生长、叶片光合能力、产量构成、土壤养分以及养分利用率的影响。结果表明：与CF处理相比，不同液体有机肥均能促进棉花生长，提高土壤有效养分含量。其中，AF处理较CF处理显著提高了棉花叶片气孔导度（G_s），增加7.18%；与CF处理相比，HF处理对棉花株高、茎粗、叶片蒸腾速率（T_r）、总根表面积的促进作用最显著，分别增加了6.38%、3.92%、11.01%和14.52%~11.84%，棉花茎和地下部干物质量最高；BF处理棉花总根长显著提高41.21%~49.48%，同时叶片净光合速率（P_n）最强，棉花单株成铃数、衣分最高，棉花蕾铃、籽棉和整株干物质量显著提高了27.91%、11.83%和9.76%。对于土壤理化性质，AF、HF和BF处理较CF处理均显著提高了土壤有效磷含量；BF处理显著降低了土壤pH，且土壤有机质、碱解氮和速效钾含量均高于其他处理。BF处理棉花肥料偏生产力、肥料农学效率和肥料贡献率较CF处理提高了5.83%~19.33%，显著高于其他处理。总之，3种液体有机肥均能促进棉花生长，增加棉花干物质积累，提高土壤有效养分含量以及肥料利用率，其中以酸性有机肥浸提液效果最佳。因此，在滴灌棉田应用酸性有机肥浸提液可以获得更高的棉花产量及肥料利用率，有利于新疆滴灌棉田可持续发展。     

Cotton responses to ultraviolet-B radiation: experimentation and algorithm development

The potential impact of an increase in solar ultraviolet-B (UV-B) radiation due to human activity on higher plants has been the subject of many studies. Little work has been carried out so far on cotton responses to enhanced UV-B radiation. The objective of this study was to determine whether or not the current and projected increases in UV-B levels affect cotton growth and development, and to quantify and develop UV-B radiation functional algorithms that can be used in simulation models. Two experiments were conducted during the summer of 2001 using sunlit plant growth chambers in a wide range of UV-B radiations under optimal growing conditions. Leaves exposed to UV-B radiation developed chlorotic and necrotic patches depending on the intensity and length of exposure. Along with changes in visible morphology, cotton canopy photosynthesis declined with increased UV-B radiation. The decline in canopy photosynthesis was partly due to loss of photosynthetic pigments and UV-B-induced decay of leaf-level photosynthetic efficiency (maximum photosynthesis) and capacity (quantum yield) as the leaves aged. The total leaf area was less due to smaller leaves and fewer leaves per plant. Less plant height was closely related to a shorter average internode length rather than a fewer mainstem nodes. The UV-B did not affect cotton major developmental events such as time taken to square, time to flower, and leaf addition rates on the mainstem. Lower biomass was closely related to both smaller leaf area and lower photosynthesis. The critical limit, defined as 90% of optimum or the control, for stem elongation was lower (8.7 kJ m⁻² per day UV-B) than the critical limit for leaf expansion (11.2 kJ m⁻² per day UV-B), indicating that stem elongation was more sensitive to UV-B than leaf expansion. The critical limits for canopy photosynthesis and total dry weight were 7 and 7.3 kJ m⁻² per day, respectively. The identified UV-B-specific indices for stem and leaf growth and photosynthesis parameters may be incorporated into cotton simulation models such as GOSSYM to predict yields under present and future climatic conditions.     

Macronutrient concentration in plant parts of cotton fertilized with broiler litter in a marginal upland soil

Effectiveness of surface-applied unincorporated broiler litter as a fertilizer relative to conventional inorganic fertilizers under no-till or conventional-till cotton (Gossypium hirsutum L.) production systems in the upland soils of the southern and southeastern USA is not well documented. The objectives of this research were to (1) test if broiler litter improves plant macronutrient (N, P, K, and Mg) nutrition of cotton above that of cotton fertilized with conventional inorganic fertilizers and (2) determine if lack of incorporating litter into the soil reduces macronutrient concentration in cotton plant parts in an upland soil considered marginal for cotton. Six treatments consisting of an unfertilized control, a fertilized standard (STD), two litter-only, and two litter plus inorganic N as urea–ammonium nitrate solution (UAN) were tested in two adjacent fields, one under no-till (NT) and the other under conventional-till (CT) systems. Litter alone, UAN, or a combination of litter plus UAN were applied to supply 101 kg ha⁻¹ plant available N assuming nearly all of the UAN-N and 50% of the total litter N becomes plant available during the cotton growing season. Concentration of N, P, K, and Mg were measured in leaves, stems, and reproductive parts on three or four dates between early flowering and maturity. Cotton fertilized with the litter-only treatments always had less N concentration but greater P and K concentration in leaves, stems, and reproductive parts than cotton that received the STD treatment. Leaf and stem Mg concentration seems to depend on the N concentration in these plant parts. Lack of incorporating litter into the soil reduced N concentration in nearly all plant parts at all growth stages, suggesting some amount of the litter-derived N is lost due to lack of incorporation. Lack of incorporation also reduced leaf and stem Mg concentration, which seemed to be due to its reducing effect on N concentration. Unlike N and Mg, lack of incorporation did not consistently affect concentrations of P and K in all plant parts. Regardless of the incorporation treatment, fertilization with the litter-only treatments increased tissue P and K concentration and supported lint yield exceeding that of the STD without increasing tissue N concentration.     

Stenotrophomonas rhizophila DSM14405T promotes plant growth probably by altering fungal communities in the rhizosphere

Stenotrophomonas rhizophila DSM14405^T is of high biotechnological interest as plant growth stimulator, especially for salinated conditions. The objective of this study was to determine the effect of plant species (cotton, tomato, and sweet pepper) on colonisation and plant growth promotion of this beneficial bacterium in gnotobiotic systems and in non-sterile soil. All plant structures (leaves, stems, and roots) were densely colonised by DSM14405^T reaching up to 10⁹ cells g^?1 fresh weight; under gnotobiotic conditions the abundances were 4–5 orders of magnitude higher than in non-sterile soil. Under non-sterile conditions and ambient humidity, tomato shoots were more densely colonised than shoots of sweet pepper and cotton. S. rhizophila DSM14405^T was shown to grow endophytically and colonise the vicinity of root hairs of tomato. Plant growth promotion was particularly apparent in tomato. In general, the impact of plant species on colonisation and plant growth promotion was more pronounced in soil than under gnotobiotic conditions and likely due to the control of diseases and deleterious microorganisms. S. rhizophila DSM14405^T was shown to control diseases in sweet pepper and in cotton. Molecular profiling via single strand conformation polymorphism of internal transcribed spacers and 16S rRNA genes (PCR-single strand conformational polymorphism (SSCP)) revealed that S. rhizophila DSM14405^T strongly affected fungal, but not bacterial communities in the rhizosphere of tomato and sweet pepper. Major SSCP bands related to uncultured fungi and Candida subhashii, disappeared in tomato rhizosphere after Stenotrophomonas treatment. This suggests an indirect, species-specific plant growth promotion effect of S. rhizophila via the elimination of deleterious rhizosphere organisms.     

Epiphytic bacterial complexes in grain crops: Taxonomic composition and antagonistic properties

It is shown that the taxonomic composition of epiphytic bacteria on the leaves of wheat and barley changes in the course of vegetation. Pseudomonas and Arthrobacter predominated on young leaves and were later replaced with the ageing of the leaves by bacteria of the hydrolytic block: myxobacteria and bacilli. Representatives of myxobacteria were found as dominants on grains in wheat and barley ears as well. Thus, the replacement of eccrisotrophs, which feed on plant excreta, with the bacteria of the hydrolytic block, which are capable of destroying dying plant tissues, was observed in the phyllosphere. Bacteria of the same taxa as those from the phyllosphere of the studied crops were isolated from the rhizosphere and the soil, where only the fraction of typical pedobionts increased, such as bacilli, Arthrobacter, and Rhodococci. It was established that the bacteria that prevail on the studied agricultural plants possess antibiotic activity toward three species of phytopathogenic bacteria used in the experiment, which indicates the protective role of epiphytic prokaryotes toward host plants.     

Decomposition of plant tissue submerged in an extremely acidic mining lake sediment: phenolic CuO-oxidation products and solid-state C NMR spectroscopy

In extremely acidic mining sediments of the Lusatian mining district, the alkalinisation process relies on organic C, which can serve as electron donor for microbially induced sulfate reduction. Plant material of the pioneer plant Juncus bulbosus is an important organic matter source in lake sediments. Therefore, decomposition of the plant tissue was assessed during the exposure of litterbags for 30 months in the 0-5 cm layer of waterlogged mining sediments, which have a pH between 2.5 and 3. The ash free dry weight (AFDW) and elemental content of the plant tissue were recorded several times during the exposure. Changes in chemical structure were analyzed by solid-state ¹³C cross polarization magic angle spinning nuclear magnetic resonance (CPMAS NMR) spectroscopy and the lignin component characterized by wet-chemical CuO oxidation. The AFDW accounted for about 34% of initial biomass after field exposure for 30 months. Mass loss of biomass occurred in two phases with decomposition rates varying between 30 and 430 mg AFDW d⁻¹. The mass loss increased considerably after 5-7 months when litterbags were invaded by fresh J. bulbosus plants. With respect to higher mass loss, ¹³C CPMAS NMR spectroscopy, showed slight changes of the bulk chemical composition after 11 months, indicating that microorganisms present in the sediments or in the rhizosphere degrade plant material as a whole, rather than selectively. During the second phase from about 11 months until the end of the exposure period, contribution of O-alkyl C most probably assignable to easily degradable polysaccharides decreased. In contrast, the contribution of alkyl, aromatic and carboxyl C increased. CuO oxidation showed that the lignin component of J. bulbosus is degraded oxidatively during field exposure. Our results indicate that the exposed plant material is decomposed in the sediment due to changes in sediment conditions that followed plant invasion of the litterbags. It is suggested that the rhizosphere of J. bulbosus by its influence on the redox potential, pH and the microbial component plays a crucial role in organic matter degradation in acidic mining sediments.     

Long-Term Effects of Aluminum and Cadmium on Growth,Leaf Anatomy,and Photosynthetic Pigments of Cotton

Aluminum (Al) and cadmium (Cd) are two elements that contaminate soil in different ways as waste products of some industrial processes and that can be tolerated by some plant species in different concentrations. In this study, growth parameters of leaves and stems (fresh and dry weights, stem lengths, leaf surface area, and lamina thickness), anatomical changes in leaves (lower and upper epidermis, stomata and mesophyll tissue), and photosynthetic pigment contents (chlorophyll a and b, total chlorophyll, and carotenoids) were investigated in cotton (Gossypium hirsutum L. cv. Nazilli 84S), which was treated with Al and Cd for 3 months. Cotton seedlings were grown in greenhouse conditions and watered with Hoagland nutrient solutions, which contained 0, 100, and 200 μM aluminum chloride (AlCl₃) and cadmium chloride (CdCl₂). It was observed that reduced soil pH positively affected many parameters in cotton plants. Aluminum accumulation was greater in leaves than stems while the opposite was true for Cd accumulation. Leaves and stems of cotton plants treated with 100 and 200 μM Al and Cd showed slight growth changes; however, high concentrations of Al (200 μM) caused significant reductions in leaf area and leaf fresh weight, whereas stem fresh weight decreased with 200 μM Cd treatment. Anatomical parameters were mostly affected significantly under both concentrations of Al and Cd solutions (100 and 200 μM). The results revealed that the anatomical changes in the leaves varied in both treatments, and the long-term effect of the tested metals did not include harmful effects on anatomical structures. Moreover, the variations could be signals of tolerance or adaptive mechanisms of the leaves under the determined concentrations.     

Characterization of resveratrol content in ten wild species of section Arachis, genus Arachis

Peanut is one of the few plants that synthesizes resveratrol, a phenolic compound of the stilbene class, which has been associated with reduced risk of developing chronic diseases, such as cancer, cardiovascular diseases, skin diseases, pulmonary diseases, diabetes and neurological diseases. Resveratrol was detected in different parts of the peanut plant, including roots, leaves, seeds and their derivatives. The wild species of the Arachis section are also strong candidates to synthesize resveratrol because they are phylogenetically closely related to cultivated peanut. Our objective was to characterize the resveratrol content in ten wild species of Arachis with three different genomes (A, B and K). The plant material was composed of leaves of the ten species treated (test) and not treated (control) with ultraviolet (UV) radiation. The test and control samples were extracted and the identification and quantification of resveratrol was performed using high performance liquid chromatography (HPLC). All species studied synthesized resveratrol and the concentrations ranged from 299.5 μg/g in A. kempff-mercadoi to 819.9 μg/g in A. cardenasii. DPPH antioxidant activity varied between 18.7 % for A. duranensis and 48.2 % in A. simpsonii. The results showed that wild Arachis species are a potential source of alleles for improvement of cultivated peanut, with the aim of achieving higher resveratrol content in leaves.     

Modelling interannual and spatial variability of leaf senescence for three deciduous tree species in France

The annual timing of temperate forest leaf colouring is affected by climate change; to date, its modelling remains a challenge. We take advantage of a ca. 400 leaf colouring observations database acquired in France during the period of 1997–2006 in order to develop a new modelling framework aimed at predicting the spatial and year-to-year variability of leaf colouring in European beech and oak (Fagus sylvatica L., Quercus petraea (Matt.) Liebl. and Quercus robur L.). We postulate colouring to be the outcome of a one-way process triggered by photoperiod and progressing through a photoperiod-sensitive cold-degree day summation procedure. Observations were pooled according to genus for the fitting and ensuing validation procedures. Parameters of the model suggest that colouring processes start earlier, and are sensitive to higher temperatures for Quercus than for Fagus. Errors associated with the modelled predictions are up to 13.0 days in Fagus and 10.3 days in Quercus, which are significantly lower than errors associated with (1) the overall mean (null model) or (2) previously published modelling frameworks. When averaged on a site basis, model predictions reproduced spatial variability of leaf colouring over the French territory with good efficiency (modelling efficiencies: 0.44 for Fagus, 0.45 for Quercus). The interannual variability of leaf colouring over France was fairly reproduced (r² = 0.74 for Fagus, 0.83 for Quercus). On that basis, we claim that the modelling framework developed herein can be efficiently integrated into more general schemes aimed at simulating matter and energy fluxes on a regional scale, and we provide a generic parameterisation of the model to be integrated into such schemes. When used in a prospective analysis, the model predicts a trend towards delay in leaf colouring of 1.4 and 1.7 days per decade in Fagus and Quercus, respectively, over the period of 1951–2099 in France.     

Dynamics of mineral nutrient element concentrations in developing cotton leaves,bracts, and floral buds in relation to position in the canopy

Plant mineral nutrient element status is an important factor influencing cotton (Gossypium hirsutum L.) growth, development, metabolism, and yield. A field study was conducted to determine changes in mineral nutrient element concentrations in leaves, bracts, and floral buds of field‐grown cotton plants during development of squares (floral bud with three bracts) as affected by fruiting position within the plant canopy. During square ontogeny, the nitrogen (N), phosphorous (P) and potassium (K) concentrations of sympodial leaves and floral bracts decreased, whereas the calcium (Ca) and magnesium (Mg) increased, and sulfur (S) concentration exhibited little change (leaves) or increased (bracts) with increasing square age. The N, P, Ca, and S concentrations in floral buds declined synchronously; K and Mg concentrations showed an increasing trend within the first 20 days, peaked at about 25‐day square age, and then sharply decreased three to five days before flowering. During square development, the effect of main‐stem node (MSN) and sympodial branch fruiting position in the plant canopy on mineral nutrient element concentrations of bracts was greater than on those of floral buds. Differences in the mineral nutrient element concentrations existed among the sympodial leaves, bracts, and floral buds. This study provides the patterns of mineral nutrient element concentrations in these plant tissues during the square development phase in relation to MSNs and branch fruiting positions in the cotton plant canopy.     

Lithium toxicity in plants

Abstract

The toxicity of Li to three plant species was studied to determine if there were interactions with other elements and to determine if a chelating agent modified Li toxicity. Bush beans (Phaseolus vulgarls L. C.V. Improved Tendergreen), grown in solution culture, were sensitive to 0.5 X10^‐3Li which resulted in 10 μg/g in leaves, 48 in stems, and 24 in roots. Higher concentrations of Li produced marked reductions in plant yield accompanied by increased Li concentrations in leaf, stem, and root tissues. For most treatments, root concentrations of Li were lower than those in shoots, but those in stems were higher than those in leaves. Higher levels of Li decreased Zn in leaves, increased Ca in stems, and generally increased Fe and Mn in all plant tissues. Ethylenediamine tetraacetic acid (EDTA) resulted in slightly increased Ii levels in leaves, stems, and roots. Bush bean plants were injured slightly with 25 μg Li/g of Yolo loam soil applied as LiCl; 50 μg Li/g soil caused more severe injury. Leaf concentrations of about 200 μg Li/g resulted in significant yield reduction and around 600 μg//g of leaves resulted in severe toxicity. There were some interactions of Li with other elements which resulted in an increase of them in both leaf and stem tissues. Barley plants (Hordeum vulgare L. C.V. Atlas 57) were severely stunted when grown with 500 and 1000 μg Li/g soil as Li oxalate. Increasing the soil pH even further with lime and decreasing it with S had no influence on the toxicity. Shoot concentrations of Li ranged from 800 to over 2000 in the various treatments resulting in severe disruption of the Ca and K balance. Leaf concentrations of Li were higher than those for stems in cotton (Gossypium hirsutum L. C.V. Acala 442). Cotton was tolerant of a leaf concentration of 587 μg Li/g. High levels of Li increased concentrations of several elements in cotton leaves and in stems. Cotton leaves accumulated more Li than did bush beans.     

INFLUENCE OF NEONICOTINOID INSECTICIDES ON THE PLANT GROWTH ATTRIBUTES OF COTTON AND OKRA

Neonicotinoids are crop protection agents used against sucking pests acting on receptor proteins of insect nervous system. Although many reports detail their insecticidal properties, reports on the effect on plant growth are minimal. We investigated the effect of neonicotinoids viz. imidacloprid, thiamethoxam, acetamiprid and thiacloprid on plant height, chlorophyll, and soluble protein of cotton and okra. Thiamethoxam was found to exert an influence on the plant height of cotton and okra. There was no marked influences of neonicotinoids on the total chlorophyll content of cotton leaves, whereas acetamiprid recorded a gradual increase in the total chlorophyll content of okra leaves at 7, 14 and 21 days after treatment. All the neonicotinoid insecticides under study showed an increase in the soluble protein content of cotton and okra. An increase in soluble protein content is reported to increase the ability of plants to fix carbon dioxide (CO₂) effectively and thus increase photosynthesis.     

滴灌条件下盐分对棉花养分及盐离子吸收的影响

在温室条件下,通过盆栽试验研究了滴灌条件下不同土壤盐度对棉花养分、盐离子吸收的影响。结果表明,棉花干物质生产受土壤盐分影响显著,高盐度条件下棉花生育进程滞后,生殖生长与营养生长不协调,造成脱落率增加,经济产量下降。土壤盐度显著影响棉花对N、P和K养分的吸收和分配;N、P和K的积累总量以及在籽棉和铃壳中的吸收量随土壤盐度增加显著降低,而茎秆和叶片受影响较小。棉花植株体内的盐分离子（Ca2+、Na+与Cl-）含量随土壤盐度的增加显著增加;吸收的盐分离子主要积累在茎叶,尤其以叶片中的盐分离子含量为最高,而籽棉的盐分离子含量较少。     

Amaranthus genetic resources in Indonesia: morphological and protein content assessment in comparison with worldwide amaranths

The morphological variations (growth habit, leaf shape, leaf color, height, stem diameter, number of branches and internodes, leaf area, blade ratio, leaf thickness, number of leaves, and total leaf area) and protein content of 53 Indonesian amaranths (Amaranthus spp.), consisting of weedy-, vegetable-, and ornamental-types, were assessed. The extent of variation in the Indonesian Amaranthus accessions were compared with the worldwide collection (26 accessions from United States Department of Agriculture (USDA) and 5 ornamentals from Nepal) in the experimental field of the University of Tsukuba, Japan. The variation in average values of most morphological traits and protein content in the Indonesian accessions were similar to those of the worldwide germplasm, but the important parameters that influence vegetable yield (e.g., number of leaves and stem diameter) were superior in the Indonesian accessions. Protein content showed a positive correlation with the number of leaves, whereas a negative correlation was observed with leaf thickness. The Indonesian accession of A. viridis and A. dubius showed a great potential to be further selected as parental lines for high protein content and number of leaves. The relatively high protein content of the leaves of Celosia may also potentially serve as an alternative protein source in the tropics.     

盛铃期补施钾肥对不同群体棉花光合特性和产量品质的影响

在大田条件下,采用随机区组设计,研究了中期(7月28日)补施75.kg/hm2钾肥对去叶枝常规密度群体和留叶枝稀植大棵群体后期棉花叶片光合特性和产量品质的影响。结果表明,两种不同类型棉花群体中期补施钾肥,均能延缓叶片衰老,保持生育后期有较高的叶面积,并能显著提高棉花生育后期主茎叶片叶绿素含量、光合效率、PSⅡ潜在光化学活性FV/FO、实际光化学效率ФPSⅡ和气孔导度Cs;显著降低非光化学猝灭系数(NPQ),从而提高了后期群体和叶片对光能的利用;有效地增加了总铃数和铃重,使子棉产量提高8.9%～9.3%,纤维比强度增强。     

Colonization of buried cotton stems by microarthropods

Initial colonization of cotton stems by microarthropods proceeded more rapidly while buried in soil under laboratory conditions (20–23°C) than while buried in the field during the winter months when soil temperatures ranged from 5–10°C in the study area in the San Joaquin Valley of California. While 15 species were found frequently in cotton stems held in the laboratory for 20 weeks, only seven species were found in field buried stems. Arthropods found under both conditions were a species of pyemotid mite; an astigmatid mite, Tyrophagus dimidiatus; two collembolans, Proisotoma minuta and Tullbergia sp.; and a sciarid fly larval stage, Bradysia impatiens. Even though the soils at teh field sites possessed a number of microarthropods in common, the stem colonization at each site was restricted to a single group which differed from each of the other sites. Microenvironments affect stem colonization patterns by microarthropods but microarthropods did not appear to have a significant influence on early cotton stem decomposition rates nor was there evidence that their activities reduced Verticillium microsclerotia populations.