梨果实贮藏中可溶性果胶和半纤维素分子结构的变化

 为了了解分子结构变化与耐藏性的关系，以耐贮性不同的苹果梨和新高梨为试材，利用Ultrogel AcA 22凝胶柱渗漏分离，比较了梨贮藏中可溶性果胶和半纤维素分子大小的变化。结果表明，苹果梨的半纤维素分子大于新高梨。在贮藏过程中，耐贮性强的苹果梨果实可溶性果胶分子大小变化不明显，但半纤维素分子明显变小。相反，新高梨的可溶性果胶分子明显变小，而未观察到半纤维素分子大小的变化。说明梨的耐贮性与可溶性果胶分子结构变化及半纤维素分子大小有关，而与半纤维素分子结构变化没有直接关系。     

Higher than optimum temperature under CO2 enrichment influences stomata anatomical characters in rose (Rosa hybrida)

There is little available information on the effects of temperature and CO₂ enrichment on stomata anatomical characteristics of plants. Effect of these two microclimates was studied on five rose (Rosa spp.) cultivars, viz. ‘First Red’ (used as check), ‘Arjun’, ‘Raktima’, ‘Raktagandha’ and ‘Pusa Pitamber’. Budded, single-stemmed rose cultivars having five lateral buds were grown in controlled environment growth cabinets under enriched CO₂ (1000 μmol mol⁻¹) and optimum (28/18 °C, T₀) or high (35/25 °C, T₁) temperature for 50 days. All observations were made on the abaxial leaf surface. Significant increases in stomatal density (68.7%), index (29.6%) and epidermal cell density (37.3%) were recorded in plants grown at high temperature over control with CO₂ enrichment. The cultivars responded differently in terms of length and width of guard cell and stoma (pore) under high temperature, however, the values averaged over treatments showed a significant reduction in these parameters. Further, number of stomata per leaf was higher (28.3%) in plants grown at high temperature, except First Red. A reduction in mean leaf area (26.7%) and dry mass (32.0%) was recorded at high rather than optimum temperature. The specific leaf area was maximum in Arjun (87%) while in First Red, a 14% reduction was noted at high temperature.     

Artificial decrease of leaf area affects inflorescence quality but not floral size in Antirrhinum majus

We have studied the effect of artificial modification of leaf area on inflorescence and floral quality in Antirrhinum majus. We used two treatments where we clipped all the leaves except the first three pairs of true leaves, or we cut every leaf visible by the time the plant had six leaf pairs. Decreased leaf area caused a decrease in stem elongation that could be traced back to a decrease in internode elongation. Leaves left on the plant increased their size beyond control. Inflorescence quality was strongly affected since total floral number showed a strong decrease with reduced leaf area. In contrast, floral size hardly changed. Breeding programs in Antirrhinum should take into account growth conditions affecting leaf area when searching for changes in inflorescence quality while floral size can be screened independently of this factor.     

风成沉积物环境敏感粒度指标的提取及意义

采用SPSS11.5软件中的主成分分析方法,对黄土高原西部末次冰期沉积的宁夏中卫冰沟剖面和兰州沙金坪剖面的粒度进行了环境敏感粒度指标的提取,沙金坪剖面和冰沟剖面的环境敏感粒级分别为24.70-27.90μm、62.47-68.97μm,冰沟剖面的阈值基本是砂粒级标准(>63μm),冰沟剖面由于距沙漠源区更近,受物源影响更大而使敏感组分更粗,不同地区的环境敏感粒度指标存在差异。另外,不同数学方法提取的指标也存在差异,数学方法的运用必须考虑其数值所表示的物理机制和环境意义。     

农牧交错带适度人口规模与人口再分布初步研究——以阴山北部丘陵区武川县为例

农牧交错带即是国家一直重视的区域也是众多专家学者高度关注的区域,作为一个生态脆弱区,人口、环境与社会经济的协调发展一直是寻根问底的问题。在众多的研究成果中多从生态环境优化、土地利用、经济发展等角度进行了探讨。本文在众多学者研究基础上,测算了土地适度人口规模、经济适度人口规模,并进一步测算了武川县乡城人口转化的进程与规模,从理论与现实角度展示了控制人口,加快转化的必要性。     

Does soil nitrogen affect early competitive traits of annual weeds in comparison with maize?

Soil nitrogen (N) is considered an important driver of crop‐weed interactions, yet the mechanisms involved have been only partially explored, especially with respect to early‐season growth, when competitive hierarchies are formed. This study characterises the effects of different N levels on biomass accumulation and plant morphology for maize (Zea mays), and four important weed species (Amaranthus retroflexus, Abutilon theophrasti, Setaria faberi, and Chenopodium album). Under glasshouse conditions, plants were grown in separate pots and irrigated with nutrient solution at four N concentrations (0.2, 0.5, 2, 5 μm L⁻¹) until 57 days after emergence. Except for S. faberi, which was unresponsive to N, the relative biomass growth rates (RGR) of maize and the broad‐leaved weeds were positively and similarly affected by increasing nitrogen. At all N levels, maize had a height advantage by virtue of its larger seed size, which conferred early growth benefits independent of RGR. At low N, biomass growth was instrumental to S. faberi’s improved competitive position, whereas height development per unit biomass improved the competitive position of A. theophrasti, C. album and A. retroflexus. The approach presented could be applied to other crop‐weed systems to evaluate environmental impacts on competitive outcomes.     

塔克拉玛干沙漠腹地纵向沙垅表面沙物质粒度特征

本文对塔克拉玛干沙漠腹地纵向沙垅表面沙粒、丘间地沙粒进行了粒度分析。结果表明,沙垅以极细沙为主,平均粒径３．０６Φ,沙粒从沙垅迎风侧到背风侧逐渐变细。沙丘沙比丘间地沙分选好,沙垅背风侧比迎风侧分选好。沙粒属极负偏,偏度－０．２２,丘间地沙比沙丘沙更趋向负偏。峰度１．３８,属尖峰态。粒径与偏度和峰度成正相关,分选和偏度成良好负相关。沙丘沙以单峰态为主,累积频率曲线为２～３段式,丘间地以双峰态为主,累积频率曲线为３～４段。大尺度地形对沙粒段式没有影响,对各段组分含量相对大小有影响。     

Evaluation of ovum storage techniques for reproductive studies of fishes

Abstract– We compared dry masses of mature oocytes and ripe eggs from Etheostoma lynceum and Etheostoma caeruleum that were stored in varying concentrations of either formalin or isopropyl alcohol. In comparison to 10% formalin, alcohol significantly reduced the weights of both mature oocytes and ripe eggs, with 25% isopropyl alcohol resulting in much smaller reductions than 50% isopropanol. Three percent formalin resulted in smaller decreases in the masses of oocytes and eggs than the alcohol treatments, and not all comparisons with 10% formalin were significantly different. We recommend fixing specimens and storing them and gametic cells removed from them in 10% formalin. In cases where specimens or eggs in alcohol must be used in addition to material in formalin, correction factors (to formalin standard) should be developed, but the correction should not be made uncritically due to the varying effects alcohol may have among samples.     

Foraging specialisms, prey size and life-history patterns: a test of predictions using sympatric polymorphic Arctic charr (Salvelinus alpinus)

Abstract –  We use arguments based on optimal foraging theory to predict body size constraints and the consequences of these on a range of life-history traits in three trophic specialist morphs of Arctic charr, Salvelinus alpinus , living in sympatry in Loch Rannoch, Scotland. As predicted, foraging specialists feeding on small prey items with a narrow size range showed evidence of deterministic growth; the ultimate body size of macrobenthos feeders being larger ( L _∞ = 238 mm) than that of planktivores ( L _∞ = 216 mm). In contrast, the piscivorous morph showed no evidence of reaching a maximal body size.
The two size-constrained morphs (benthivores and planktivores) matured earlier and died younger (living for up to 11 and 7 years, respectively, in this study) than did the piscivorous charr which showed continuous growth up to at least 17 years.
The pattern of annual reproductive investment in maturing individuals was complex. Planktivores invested in larger eggs than the other two forms, but benthivores produced a greater number of eggs than planktivores, which in turn produced more than piscivores. Planktivorous males had a greater investment in mean testis weight than the other two forms.
Lifetime reproductive output was the greatest in the benthivorous charr, intermediate in planktivorous and the lowest in the piscivorous charr when measured either as fecundity or as gonadal weight. We conclude that constraints imposed upon foraging specialists by foraging efficiency is a significant driver of body size and ultimately reproductive investment in gape-limited foraging salmonids.     

粘粒含量——夏季风的良好替代指标

通过对位于东亚季风区尾闾部位的沙沟剖面、东部半湿润区王官剖面、东部湿润区扣马剖面的气候代用指标的分析发现 ,黄土地层中 <5 μm的粘粒含量指标对各剖面中黄土-古土壤序列指示得比较清晰 ,可以较好地反映东亚夏季风的变化。对黄土地层中粘粒含量的测试及其环境意义分析以及与经典的东亚夏季风的替代指标———磁化率、红度指标 (a )的对比分析发现 ,粘粒含量指标的意义比较明确 ,适应范围更广 ,灵敏性也较高 ,是一比较可靠的、新的东亚夏季风的良好替代指标。