气孔下腔间的水汽扩散

本文把气孔及其下腔看作截面为椭圆形的柱形区域,提出一个水汽从气孔下腔内所有细胞表面扩散到气孔外端的三维扩散模型。根据 Fick 定律和质量守恒定律建立了支配该模型的水汽扩散方程。用有限差分法,借助于计算机求得水汽从气孔下腔的所有细胞表面扩散到气孔内端所遇到的阻力及其近似表达式。并从理论上对该阻力的倒数——导度随气孔面积而变化的方式做了分析和解释。通过将本模型求得的气孔下腔阻力计算公式与 Brown 等以及 Cooke 的公式比较,发现在气孔开度变化相当大的范围内用后面两公式计算的阻力偏大0.5—1倍左右。此外,计算结果还表明:在气孔下腔水散失总量中,腔内表皮细胞表面上的水散失量占86—96%,而保卫细胞表面上的水散失量又占后者的88—93%,副卫细胞表面上的水散失量仅7—12%。     

小哺乳动物在高寒环境中的生存对策 Ⅰ.高原鼠兔和根田鼠褐色脂肪组织(BAT)重量和显微结构的季节性变化

本文研究了高寒草甸生态系统中两种非冬眠草食性哺乳动物——高原鼠兔和根田鼠的褐色脂肪组织(BAT)的重量和显微结构的季节性变化,结果表明严寒季节BAT增多、BAT细胞中的脂肪滴小而多、线粒体增大及嵴数目增多,温暖季节较低,这些变化与产热需要有关。     

猪生长激素cDNA的全序列分析

本文报道了两个猪生长激素cDNA的全序列分析的结果。猪生长激素cDNA是我们由猪垂体mRNA经过反向转录、克隆和筛选后获得的。文中还将这两个序列与Seeburg等(1983)报道的序列以及Vize等(1987)报道的猪基因组生长激素基因的序列进行了比较和讨论。     

植物绿叶对光的吸收规律的实验研究

实验结果表明:(1)光线照射到植物绿叶时,光的反射不仅仅发生在叶子表面,还发生在表面以下各组织层;(2)在190—860nm之间,绿叶在190—500nm段出现一个吸收区,在680nm处出现一个吸收峰,它们的吸收比均高达85％以上;(3)虽然710—750nm的红光对叶片的反射比大于500—570nm的绿光,但人眼看到叶片仍然是绿色,我们对这一现象进行了解释。本文将为研究绿叶的光学性质和光合作用等提供有用的参数。     

Control of Seed Respiration and Growth in Vicia faba by Oxygen and Temperature: No Evidence for an Oxygen Diffusion Barrier

The rate of dry matter accumulation by seeds of Vicia faba L. cv. Minica increases with temperature in the range of 16 to 26°C. The duration of dry matter accumulation decreases with temperature, resulting in a decrease of final seed dry weight. In this study we test the hypothesis that a diffusion barrier for O₂, located in the seed coat, inhibits seed respiration and growth. The rate of O₂ uptake of intact seeds and of excised embryos and seed coats (separated seeds) was measured in air and buffer at 16, 20, and/or 26°C at various O₂ concentrations and developmental stages. Oxygen uptake rates of intact seeds in buffer were only 9 to 15% of those in air. In buffer, the respiration rate of intact seeds decreased at a pO₂ below air saturation (21 kilopascals), whereas separated seeds showed a decline of O₂ uptake only below 80% of air saturation. In air, embryo excision had no effect on the sensitivity of seed respiration to pO₂, at both 20 and 26°C. In air at 20°C, separated and intact seeds showed similar rates of O₂ uptake. Oxygen uptake by intact seeds, both halfway and beyond the linear growth phase, showed a temperature coefficient Q₁₀ of 2.3 and was insensitive to pO₂ in the range of 80 to 100% of ambient. These results indicate that V. faba seed respiration in air is not limited by the diffusion of O₂ into the seed.