Monitoring stomatal conductance of Jatropha curcas seedlings under different levels of water shortage with infrared thermography

Model simulations and experimental measurements were used to investigate the applicability of infrared thermography for the estimation of stomatal conductance and drought stress under sub-optimal meteorological conditions. The study focused on the stomatal conductance index I_g, calculated from the leaf temperature and the temperature of a dry and wet reference leaf. The simulations revealed that I_g is influenced by leaf dimension, wind speed and air temperature and not or hardly by leaf angle, albedo, relative humidity or insolation. In addition, I_g was found to be very sensitive to differences in wind speed, air temperature, insolation, leaf dimension and leaf angle between the measured and the reference leaves. In the experimental part, we evaluated if infrared thermography can be used to improve the knowledge on the water use of Jatropha curcas L., a tropical biofuel crop. Thermal images from Jatropha seedlings grown under three different drought treatments were made on a day with very variable insolation and a day with very low insolation. Smaller newly formed leaves and the active control of the leaf angle proved efficient ways of Jatropha to protect leaves under drought stress from overheating. I_g, assessed in four different ways, and four simplified drought stress indices were derived and related to the measured stomatal conductance (g_s) of the seedlings. The strongest correlation with g_s and the highest discriminative power between the different water treatments were achieved when I_g was calculated by taking the average leaf temperature per plant and the temperature of the dry and wet reference leaves of this plant, rather than the average temperature of several reference leaves. Using the difference between the dry reference and the measured leaf (T_dry − T_l) as a simplified index gave similar results, although correlations were weaker. Other simplified thermal indices were not well correlated with leaf stomatal conductance or with water treatment. Recommendations were formulated for the measurement of I_g and (T_dry − T_l).     

葡萄果实在压缩载荷作用下的力学模型(英)

建立了葡萄的非线性力学模型。把葡萄简化成球形的、均匀的、各向同性的和内部充满不可压缩液体的弹性膜。研究了葡萄在压缩载荷作用下的应力分布和变形。利用膜理论建立了接触区域与非接触区域的平衡方程，确定了边界条件与连续条件。利用Runge-Kutta方法，进行数值求解，得到了在压缩载荷作用下葡萄的张力。结果表明：在压缩载荷作用下，葡萄纬线方向的张力大于经线方向的张力，最大拉力发生在赤道平面上，葡萄在压缩载荷作用下的损伤主要是由最大拉应力造成的，该结论与试验观察的结果相一致。     

The exploitation of helix pomatia L.

The evidence at present available, although incomplete, gives rise to fears for the future of the edible snail Helix pomatia L. The scale of exploitation is increasing, particularly in Eastern Europe, to meet growing demand, mainly from the West. The growth of legislation to control collecting supports the evidence of declining numbers, but the legislation does not appear to be backed by sufficiently detailed population ecology studies. The need for co-ordinated international action on farming, legislation and ecological study is urged.     

麻疯树复垦酸性矿山废弃地及其生长影响因子研究

粤北大宝山矿开采产生大量的毒性金属,严重地威胁着矿区周边地区的土壤和水体环境[1],给矿区周边居民的身体健康造成巨大威胁[2]。因此,解决大宝山矿区周边环境的重金属污染已刻不容缓。目前,在矿山重金属污染土壤的修复技术中,植物复垦因具有成本低、效益高的优点而成为合适的修复技术[3]。其可以通过向土壤中添加改良剂来降低金属迁移和生物有效性,并通过所种植的金属耐性植物的根部积累、表面吸附或根际沉积作用来稳定土壤中的重金属,从而降低人类或动物接触重金属污染物的风险[3-4]。理想的耐性植物应该能耐受极端环境、具有非食用性及经济价值的特点,然而目前这类植物的报道较少[5]。麻疯树(Jatro-pha c     

大蒜种瓣机械压变处理对其出苗及生长的影响（英文）

为探明大蒜种瓣机械压变处理对大蒜出苗及生长的影响规律,以东北白皮蒜为研究对象,利用万能物理试验机对大蒜种瓣进行横向施压（大蒜种瓣平放受压）和纵向施压（大蒜种瓣直立受压）,以受压变形量与原基本尺寸比值的百分数来表示受压程度,2个方向受压程度为5%～45%,取一组未处理的大蒜种瓣作为对照。将处理后的大蒜种瓣与对照进行播种试验,探索机械压变处理对大蒜出苗天数、出苗率、植株茎粗和植株高度的影响,通过回归分析得出植株茎粗与施压程度之间的回归模型,并进行植株高度与施压程度之间的相关性分析。试验结果表明,与未处理的大蒜种瓣相比,横向受压中,受压程度为10%～45%时,机械压变对大蒜种瓣出苗天数、出苗率、植株茎粗和植株高度有显著影响（P<0.05）,其中受压程度为10%～25%的大蒜种瓣出苗时间短于对照,出苗率、植株茎粗和植株高度均大于未处理的大蒜种瓣;在纵向受压中,受压程度为10%～45%时,机械压变对大蒜种瓣出苗天数、出苗率、植株茎粗和植株高度有显著影响（P<0.05）;其中受压程度为10%～15%时,大蒜种瓣出苗时间均长于对照,出苗率和植株茎粗均大于未处理的大蒜种瓣。相比纵向机械压变处理,横向机械压变处理的大蒜出苗快,相同压缩条件下,大蒜的各项指标更优。植株茎粗与施压程度之间的回归模型拟合较好（R≥0.91）,植株高度与施压程度之间的相关性显著(P<0.05)。     

大蒜种瓣机械压变处理对其出苗及生长的影响

为探明大蒜种瓣机械压变处理对大蒜出苗及生长的影响规律,以东北白皮蒜为研究对象,利用万能物理试验机对大蒜种瓣进行横向施压(大蒜种瓣平放受压)和纵向施压(大蒜种瓣直立受压),以受压变形量与原基本尺寸比值的百分数来表示受压程度,2个方向受压程度为5%～45%,取一组未处理的大蒜种瓣作为对照。将处理后的大蒜种瓣与对照进行播种试验,探索机械压变处理对大蒜出苗天数、出苗率、植株茎粗和植株高度的影响,通过回归分析得出植株茎粗与施压程度之间的回归模型,并进行植株高度与施压程度之间的相关性分析。试验结果表明,与未处理的大蒜种瓣相比,横向受压中,受压程度为10%～45%时,机械压变对大蒜种瓣出苗天数、出苗率、植株茎粗和植株高度有显著影响(P0.05),其中受压程度为10%～25%的大蒜种瓣出苗时间短于对照,出苗率、植株茎粗和植株高度均大于未处理的大蒜种瓣;在纵向受压中,受压程度为10%～45%时,机械压变对大蒜种瓣出苗天数、出苗率、植株茎粗和植株高度有显著影响(P0.05);其中受压程度为10%～15%时,大蒜种瓣出苗时间均长于对照,出苗率和植株茎粗均大于未处理的大蒜种瓣。相比纵向机械压变处理,横向机械压变处理的大蒜出苗快,相同压缩条件下,大蒜的各项指标更优。植株茎粗与施压程度之间的回归模型拟合较好(R≥0.91),植株高度与施压程度之间的相关性显著(P0.05)。     

The mechanical behavior of structured and homogenized soil under repeated loading

Soil deformation is increasingly important in crop production since nowadays weights of agricultural machines exceed the bearing capacity of most soils. Often this is counteracted by distributing the weight over more axles leading to an increase in wheeling frequency. Machine passages during one year can, depending on the crop and equipment used, range between two and five times for the majority of the field and up to twenty times and more for a wheeling track. These add up to hundreds of loading events for a crop‐rotation period. In this study, we investigated the effect of multiple loading with the same load in a cyclic‐compression test on soil‐pore‐volume change. The tests were conducted on homogenized soil samples with varying texture and undisturbed soil samples from a field experimental site comparing conventional and conservation‐tillage systems. Of particular interest was the question whether there is significant plastic soil deformation for soil stresses that remained sufficiently below the precompression stress, which is commonly neglected. Our results show that especially for cohesive soils, the assumption of fully elasticity in the recompression range may not be justified since those soils show distinct cyclic‐creep behavior. We found that deformation under cyclic loading follows a logarithmic law. We used the slope of the logarithmic fit of void‐ratio changes vs. loading cycles as a parameter to characterize the sensitivity of soils to cyclic compression. The results suggest that for characterizing the mechanical stability of soils that show cyclic creep, we have (with respect to long‐term deformation effects) to consider both precompression stress and cyclic compressibility.     

河套蜜瓜机械特性与静载损伤关系的研究

为解决河套蜜瓜在储运过程中因静载产生的机械损伤问题,通过对不同条件下完整形态的河套蜜瓜静载破坏时损伤体积的测定和分析,研究了河套蜜瓜机械特性以及各试验因素、机械特性参数对破坏损伤体积的影响.试验结果表明,屈服极限和变形能在随载荷速率增大而增加的过程中有极值现象存在,而破坏极限与破坏能则随载荷速率增大而持续增加;随果实硬度降低,屈服极限、变形能、破坏极限、破坏能等指标均明显降低;试验获得了完整近球形蜜瓜果实的应力-应变曲线,应力-应变曲线反映出完整形蜜瓜在受压初期载荷增长滞后于受压面积的增长.试验结果同时表明,河套蜜瓜准静载机械特性参数、影响因素如载荷速率、果实硬度、加载部位等对果实受压产生的机械损伤均有明显影响,缓慢加载使果实内部微观组织较早出现破坏,易扩大损伤体积,受压后果实的损伤体积较大;垂直受压使果实破坏后产生的损伤体积大于果实水平受压时的损伤体积.建立了完整形河套蜜瓜准静载机械特性参数、影响因素与蜜瓜果实损伤体积的回归方程.数据分析表明,所建立的回归方程是有意义的,可以用其预测和控制河套密瓜储运过程中的静载损伤.机械特性参数之间均存在一定相关性,其中生物屈服极限与变形能的相关程度最高(r=0.870),生物屈服极限与破坏极限的相关程度最小(r=0.366).     

不同温度条件下玉米种子发芽的量化模型

选用龙单５、四单１９和吉单１５９三个不同熟期的玉米品种做发芽试验,控制温度分别为１３℃、１７℃、２１℃和２５℃,研究不同温度条件下玉米种子发芽与经历时间的关系,结果表明,各个品种在不同温度条件下的发芽率与经历时间符合生长曲线函数ｙ１＝Ｃ／（１＋ｅ＾ａ＋ｂｘｉ）。     

Does the acephaline gregarine Monocystis sp. modify the surface behaviour of its earthworm host Lumbricus terrestris?

The earthworm Lumbricus terrestris has relatively low dispersal rates. This can represent a challenge for the internal gregarine parasite Monocystis, the dispersal of which often depends on the host. Mating of Monocystis can also be restricted to parasite stages within the current host individual. Adaptations, including host behavioural modification, that improve parasite transmission and simultaneously avoid inbreeding within a single host individual should be favoured by selection. We used a correlative approach to investigate the question of parasitic manipulation in this Gregarine-Lumbricid system. We observed mature earthworms (n=24) for 3 weeks while recording various measures of activity (surface activity, burrowing activity, surfacing delay, number of surface visits) and correlated parasite load with these activity measures. We found a significant positive correlation between surface activity and midden (or cast) production, which suggests a simple method for assessing the overall activity of local earthworm populations. However, we found no evidence of behavioural manipulation of any measure of host activity. We discuss these results in the context of inbreeding depression and host-parasite coevolution.     

Food quality affects production of Lumbricus terrestris (L.) under controlled environmental conditions

Birch leaves and horse manure were used to determine the effects of food quality on growth and reproduction of laboratory-reared Lumbricus terrestris. Animals grew to maturity within 6 months but attained a significantly (p < 0.001) larger adult size with manure (6.17 g) versus leaves (4.20 g). Cocoon production by recently-mated adults maintained in isolation, fed with birch leaves or horse manure, resulted in 4.53 and 3.84 cocoons ind.⁻¹ month⁻¹ respectively, with an initial hatchability of 86%, falling to zero after 18 months. Re-mating of these known individuals permitted long term monitoring of reproductive output (to 30 months). For the whole experimental period, overall hatchability of the 2010 cocoons produced was 44.4%. Median incubation time of those cocoons that hatched within accepted norms (less than 5 months at 15 °C) was 103 days and was not influenced by adult food type. A proportion (35.5%) of cocoons took in excess of 12 months to hatch. Adult mortality was minimal (25%) during the long term experiment but abnormal cocoon production was recorded after 2 years. Overall results demonstrate that food quality can have a significant influence on somatic and reproductive production of L. terrestris and these data may aid construction of production models for this earthworm in ecosystems with contrasting food quality.     

The value of white clover Trifolium repens L., Cultivar S100 planted on motorway verges to honeybees Apis mellifera L.

During two years the preferences shown by bees for five cultivars of white clover (S100, S184, Sabeda, Kent Wild and New Zealand Huia) were tested. Honeybees and bumblebees visited all the cultivars, but S100, the cultivar commonly planted on motorway verges, was one of the most attractive to them.     

基于准静态压缩的果实黏弹塑性模型

目前对果实黏弹塑性特征与模型进行表征比较困难。基于果实等速压缩变形特征,提出了一表征其黏弹塑性的流变模型。该模型包括3个非线性弹簧元件、一个黏性元件以及一个滑块元件。结合压缩应力—应变试验曲线特征与模型特性提出了模型参数的数值确定方法。采用梨果实全果肉、带核果肉两种试样进行试验,获得了其黏弹塑性模型参数。结果表明试验与理论模型结果非常吻合,果核对其黏弹塑性有较大影响。采用本模型结合试验结果能较准确简便地确定类似特性果实的流变特征参数。研究结果为果品黏弹塑性流变特性分析以及模型表征提供了一种新的方法。     

Ecological history of yew Taxus baccata L. In Southern England

Yew was widespread but uncommon during the post-glacial period, though planting has extended its natural range and abundance. However, it is now common on the chalk hills of southern England as a dominant or minor species. Rainfall and humidity appear to influence its distribution on the South Downs. A developmentas study of yew-dominated woods on the Hampshire-Sussex border showed they originated on abandoned sheep down or rabbit warrens, as a result of rapidly changing agricultural practices during the last two centuries. Yew woods occur on high, steep slopes, often along parish boundaries, and their possible origin from parental seed trees marking those boundaries is discussed. It is suggested that they are a seral stage of secondary scrub; this has implications for their long-term conservation. The present conservation measures regarding 16 yew woods on the South Downs are described.     

Biological activity of alpha-galactoside preparations from Lupinus angustifolius L. and Pisum sativum L. seeds.

Biological activity tests were performed on alpha-galactoside preparations obtained from Lupinus angustifolius L. cv. Mirela (alkaloid-rich) and Pisum sativum L. cv. Opal seeds. The studies included the following tests: acute toxicity, cytotoxic test, delayed type hypersensitivity (DTH), plaque-forming cell number (IgM-PFC), and influence on the growth of bifidobacteria and coliform presence in rat colon. Results of these studies showed that alpha-galactosides from lupin and pea seeds were essentially nontoxic. Their acute toxicity (LD(50)) in mice was >4000 mg kg(-1) of body weight. alpha-galactoside preparations were not cytotoxic for mouse thymocytes in vitro. The in vitro test shows that oligosaccharides from lupin and pea are utilized by selected beneficial colon bacterium strains. The in vivo experiment demonstrated that alpha-galactosides from legume significantly influenced the growth of bifidobacteria in rats colon. Simultaneously, the decrease of the coliform presence was observed. The chemical composition of the tested preparations had no significant effect on their biological activity.     

Studies of field populations of rhizobium: Effectiveness of strains of rhizobium trifolii associated with trifolium subterraneum L. pastures in South-Eastern Australia

Field populations of Rhizobiuin trifollii from eight regions in south-eastern Australia were sampled over a period of 5 years from 1966 to 1970. The R. trifolii isolates were tested under bacteriologically-and environmentally-controlled conditions for effectiveness of nitrogen fixation in combination with Trifalium subterraneum L. cv. Bacchus Marsh; the effective strain TA1 was used as a standard of comparison.Mean effectiveness of the R. trifolii populations for any region at any sampling varied between 62 and 93 percent of the effectiveness of the standard strain. The principal feature was the large variability within sampling sites, between sites within paddocks, and between paddocks within regions. In addition there was some variability with time in the range of effectiveness values of isolates within a site and in the absolute values for both sites and paddocks. Effectiveness values were not related to soil pH, size of population of R. trifolii, inoculation procedure at sowing, age of pasture, annual rate of fertilizer application, or mean annual rainfall.     

Aggregate strength and mechanical behaviour of a sandy loam soil under long-term fertilization treatments

Current concern for soil quality has stimulated research on soil biological and chemical properties. In contrast, the mechanical behaviour of soil is somewhat neglected. We have examined the effects on soil mechanical properties of more than 100 years of contrasting fertilization employing three treatments from the Askov long‐term experiment: UNF (unfertilized), NPK (mineral fertilized) and AM (animal manured). We have measured tensile strength of aggregates when air‐dry and when adjusted to ?10, ?30 and ?100 kPa pressure potential. Four aggregate size classes were investigated (1–2, 2–4, 4–8 and 8–16 mm diameter). Soil fragmentation was characterized in the field using a drop‐shatter test. Bulk soil strength was determined in the field using a shear vane and a torsional shear box. Soil texture, pH, cation exchange capacity and microbial biomass were measured. The unfertilized soil has little soil organic matter and microbial biomass and is dense. Its aggregates were strong when dry and weak when wet. In contrast, the manured soil had strong aggregates when wet and rather weak ones when dry. The NPK soil generally had intermediate properties. The differences between the soils when dry seem to be related to differences in dispersible clay content, whereas the differences when wet are related to differences in the amount of organic binding and bonding material. The optimal water content for tillage as well as the tolerable range in water content was largest in the manured soil and smallest in the unfertilized soil. Our results indicate that soil mechanical properties should be measured over a range of water regimes to determine the effects of various long‐term fertilization treatments.