大针茅典型草原土壤CO2排放规律的研究

采用静态室/碱吸收法研究了内蒙古大针茅典型草原土壤呼吸的时空动态.大针茅群落地上部和地下部生物量的时空变异不同步,用地上部生物量不能很好地预测群落的根系量.群落土壤呼吸具有明显的时空动态,控制群落土壤呼吸空间变异与时间变异的因子是不同的.土壤呼吸的季节变化与地上部生物量及土壤水分状况关系密切.根据大针茅群落分别计算了大针茅群落1995、1997和1998年的年CO₂排放总量,分别为180、45.8和225gC·m^-2·a^-1,年际变异很大.过度放牧大大降低了群落的生物量,也降低了土壤CO₂排放量.讨论了建立以降水量为驱动因子的草地群落土壤呼吸动态模型的可能性.     

福建省中部地区抗寒速生尾巨桉优株筛选

本文通过自然选择与优势木选择方法,选择了适生性状良好的尾巨桉品种的多个优良单株。根据不同选择标准,筛选出抗寒适生优良单株21株,抗寒速生优势木单株13株;对所选单株采用无性系繁殖方法,利用1000mg/L ABT生根粉处理所选择优良单株的穗条,用营养袋扦插培育无性系种苗,并建立无性系采穗圃和优良单株基因库。     

巨桉人工林地土壤微生物类群的生态分布规律

研究了四川省洪雅县巨桉人工林地土壤微生物数量及其类群分布规律.结果表明,洪雅县巨桉人工林地土壤微生物数量具有明显的季节变化,各样地均以秋季最多,达到17.42×10⁶CFU·g^-1,春季次之,夏季最少.土壤微生物主要集中在0～20cm的土层,随着土层的加深,微生物数量迅速减少;在0～60cm土层,同一类群微生物数量变动范围较大,其中好气性细菌0.31×10⁶～14.39×10⁶CFU·g^-1,放线菌0.06×10⁶～0.79×10⁶CFU·g^-1,真菌0.02×10⁶～0.07×10⁶CFU·g^-1,厌氧细菌0.07×10⁶～3.22×10⁶CFU·g^-1.巨桉人工林地微生物以细菌为主要类群,占微生物总数的92.83%以上,其次是放线菌和真菌,其微生物组成结构合理.与青冈次生林和农耕地相比,巨桉人工林地微生物数量远远高于青冈次生林地,有利于土壤微生物生长.细菌生理类群的Simpson多样性指数和Shannon-Wiener多样性指数分别达到0.773和1.896.     

不同放牧强度下内蒙古温带典型草原优势种植物防御策略

放牧是草原的主要利用方式, 但对牧草造成了一定的生物胁迫。面对生存压力, 牧草会通过调节初级与次级代谢过程启动防御机制。该研究以内蒙古温带典型草原优势种植物为研究对象, 通过测定其在5个放牧水平下不同营养器官中的次级代谢产物及木质素等含量, 探讨大针茅(Stipa grandis)和羊草(Leymus chinensis)的各营养器官在防御机制中的角色及其碳氮权衡策略。结果表明: 面对放牧胁迫, 大针茅和羊草会产生大量的单宁、总黄酮、酚类以及生物碱等次级代谢产物, 并以叶片为主要的合成及储存器官。中度放牧使羊草的化学防御机制得到较充分的诱导及表达。但二者地上部分木质素含量并无显著增加, 因此, 二者在避牧性机制上更倾向于化学防御而非机械防御。由于羊草有更高的氮利用效率, 这使得羊草可以通过碳氮两种代谢途径进行防御, 但大针茅在生长初期并不能将氮高效地分配到化学防御中。大针茅和羊草在生长初期面对轻度放牧胁迫, 较多的资源仍然用于初级代谢, 增加了植物耐牧性。因此, 轻度放牧有利于提高牧草的碳氮资源利用效率、提高生态系统生产力及稳定性。     

巨枝叶绿体基因组密码子偏好性分析

该文针对巨桉叶绿体基因组序列,选取其中长于300 nt且以AUG为起始密码子的43个非重复基因作为研究对象,采用CodonW1.4.2软件分析巨桉叶绿体基因组的密码子使用偏好性。结果表明:第3位密码子的平均GC含量为27.97%; ENC的变化范围为39.49～61.00,平均为47.04; RSCU1的密码子有31个,其中29个以A/U结尾;中性分析显示,GC12与GC3无显著相关;回归分析未达到显著性水平; ENCplot分析发现,大部分基因落在曲线上或附近;对应分析表明第1轴的贡献率为17.68%,第2轴的贡献率为11.49%,第3轴、第4轴的贡献率分别为8.00%和5.76%,前4轴累计贡献率达42.93%,第1轴与GC、ENC、CAI达到极显著相关。上述分析结果表明,巨桉叶绿体基因组的密码子偏好较弱,密码子第3位偏好以A或U结尾,选择和突变在巨桉叶绿体基因组密码子偏好中起相对均衡的作用,最终确定UUG、CUU、GUU、UCC、UCA、ACA、UAU、UAA、CAU、AAU、AGA和GGA 12个高频高表达密码子为最优密码子。这为转化叶绿体基因密码子优化,提高表达效率和改良巨桉目标性状奠定了坚实基础。     

Photosynthetic and stomatal responses of two tropical and two temperate trees to atmospheric humidity

The effects of leaf to air vapour pressure differences (ΔW) on net photosynthetic rate (P_N) and stomatal conductance (g_s) were examined in the leaves of two tropical rain forest trees, Eugenia grandis and Pongamia pinnata, and two temperate evergreen trees, Viburnum awabuki and Daphniphyllum macropodum. A single leaf was set inside a small chamber and ΔW was varied from 7 to 24 mmol mol^-1 at 25 and 500 μmol m^-2 s^-1 of photon flux density. P_N and g_s of the two tropical rain forest trees decreased with increasing ΔW, while the two temperate evergreen trees were not highly responsive to ΔW. P. pinnata was more sensitive to ΔW in its stomatal response, and had a higher stomatal density and higher stomatal index than did the two temperate trees and another tropical tree. Significant reductions i n g_s and intercellular CO₂ concentrations in the two tropical trees at high ΔW suggest that the decline of P_N was due to the decrease in g_s. The responses of P_N and g_s indicated that the tropical trees were more sensitive to ΔW than were the temperate ones. This revised version was published online in September 2006 with corrections to the Cover Date.     

琯溪蜜柚汁囊分化和粒化过程的解剖学观察

用徒手切片、石蜡切片、细胞化学等方法观察了琯溪蜜柚（Ｃｉｔｒｕｓ　ｇｒａｎｄｉｓ（Ｌ．）Ｏｓｂｅｃｋ）汁囊的分化和粒化过程。结果表明,心皮内表皮细胞和表皮下细胞分裂共同形成汁囊原基。由汁囊原基发展成柱状结构。柱状结构顶端有类似分生组织的细胞群,中心有类似分生组织的细胞柱。它们的细胞呈多角形,细胞核大,原生质浓厚。类似分生组织的细胞柱纵贯柱状结构中心（除柄部外）。开花后７周近柄端明显分化。开花后约两个半月,汁囊雏形形成。汁囊的粒化分为４个阶段：（１）正常汁囊阶段,汁囊透明,切开溢出果汁。表皮下细胞为角隅加厚的厚角组织,个别薄壁组织细胞原生质体已死亡。（２）凝胶化阶段,汁囊透明、坚挺,切开为凝胶状,表皮下细胞区的厚角组织细胞壁全面加厚。有的汁囊中已有部分细胞的细胞壁木质化。（３）粒化阶段,汁囊乳白色或部分乳白色。表皮、表皮下细胞区、长细胞区和汁细胞区等四个细胞区均有较多细胞的细胞壁木质化加厚。（４）粒化后期,汁囊黄白色,部分硬化,部分萎缩,汁囊变形,硬化部分大部细胞木质化,萎缩部分死亡的细胞被挤压,随果实贮存时间延长,正常汁囊减少,汁囊中淀粉量减少,油滴增多。     

THE GENUS BALLIELLA ITONO & TANAKA (RHODOPHYTA: CERAMIACEAE) FROM EASTERN AUSTRALIA1

Three new species of the genus Balliella Itono & Tanaka are described from eastern Australia. Balliella amphiglanda from Lord Howe I. and Port Hacking, N.S.W., is distinctive in producing either abaxial or adaxial gland cells from the basal cells of lateral branches and in having tetrasporangia restricted to short branches. Balliella repens, from Tryon I., Heron I and Wistari Reef Qld., and Lord Howe I., N.S.W., is distinguished from the other species of the genus by its regularly developed prostrate systems and clustered tetrasporangia. Balliella grandis, from Wistari Reef, North West I. and One Tree I., Qld., is the largest recorded species of Balliella. It has correspondingly large gland cells and abaxial as well as adaxial tetrasporangia. Our work supports the placement of Balliella in the tribe Antithamnieae, a move which necessitates emending Wollaston's definition of the tribe to include species with procarps that form at successive levels along main axes rather than at only one or two points behind the apices.     

Effects of host on functional response of offspring in two populations of Trissolcus grandis on the sunn pest

Trissolcus grandis Thompson is the most important egg parasitoid of Eurygaster integriceps Put. in Iran. It can be reared on some alternative hosts such as eggs of Podisus maculiventris (Say). In this study, the functional response of female wasps that emerged from the factitious host, P. maculiventris, has been compared with that of females that emerged from the primary host, E. integriceps. In both wasp groups, at 23 ± 1°C, 70 ± 10% relative humidity and 15.00 : 9.00 hours (L : D) photoperiod, a type III functional response was observed. Parameters of Holling's disk equation for both populations were estimated and compared with an equation with indicator variable. Estimated handling time for females that emerged from Eurygaster and Podisus eggs are 0.62 and 0.77 h and parameter b, which describes the change in attack rate with host density in a type III functional response, was 0.004 and 0.005, respectively. The results indicated that the functional responses of the two populations differed in handling time. Longer handling time in wasps that emerged from factitious host showed that the wasps have lower quality in comparison with the wasps that emerged from primary host. This may be the first evidence of the effect of host on functional response of offspring and a promising result for use of functional response in quality testing.     

香榧与油茶籽中脂肪酸成分的GC-MS分析

用石油醚提取香榧与油茶籽油,经过皂化、甲酯化处理,利用气相色谱-质谱(GC-MS)联用技术对其脂肪酸组成进行了检测。研究结果表明:香榧籽油共检测出6种脂肪酸,油茶籽油中共检测出5种.均以油酸和亚油酸为主。其中,香榧籽油中二者占总量的67.91%.油茶籽油中二者占总量的51.38%.本文对比分析了香榧籽油和油茶籽油中脂肪酸的主要成分及含量,为这两种木本食用油的开发利用提供理论基础。