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991.
Hydraulic architecture and water relations of Spartium junceum branches affected by a mycoplasm disease 总被引:1,自引:0,他引:1
Plant water relations, xylem anatomy and the hydraulic architecture of 1‐year‐old twigs of Spartium junceum, both healthy and affected by a phytoplasm disease, were studied. The disease causes twigs to be either shortened (witches broom disease, WBD) or flat (fasciate disease, FD). WBD twigs show a sevenfold increase in total leaf area, smaller and shorter xylem conduits, a higher stomatal conductance (gl) and a decline of minimum leaf water potentials ( Ψ l) below the turgor loss point. FD twigs had nearly twice the leaf area of the healthy controls as well as high gl values and Ψ l values below the turgor loss point. Moreover, significant differences between healthy and affected twigs in stem stomatal conductance (gs) and in the total stem area were recorded. Affected twigs die back under drought stress, which is explained by a pronounced loss of hydraulic conductivity of the infected stems (40 and 60%) in FD and WBD as well as by the unfavourable ratio of weighted conduit radius ( Σ r4) to total surface area (At), so that the efficiency of the stem in supplying the whole transpiring area with water is strongly reduced. 相似文献
992.
Tansley Review No. 119 总被引:2,自引:0,他引:2
993.
Competition in tree row agroforestry systems. 1. Distribution and dynamics of fine root length and biomass 总被引:4,自引:0,他引:4
Complementarity in the distribution of tree and crop root systems is important to minimise competition for resources whilst
maximising resource use in agroforestry systems. A field study was conducted on a kaolinitic Oxisol in the sub-humid highlands
of western Kenya to compare the distribution and dynamics of root length and biomass of a 3-year-old Grevillea robusta A. Cunn. ex R. Br. (grevillea) tree row and a 3-year-old Senna spectabilis DC. (senna) hedgerow grown with Zea mays L. (maize). Tree roots were sampled to a 300 cm depth and 525 cm distance from the tree rows, both before and after maize
cropping. Maize roots were sampled at two distances from the tree rows (75–150 cm and 450–525 cm) to a maximum depth of 180
cm, at three developmental stages. The mean root length density (Lrv) of the trees in the upper 15 cm was 0.55 cm cm−3 for grevillea and 1.44 cm cm−3 for senna, at the start of the cropping season. The Lrv of senna decreased at every depth during the cropping season, whereas the Lrv of grevillea only decreased in the crop rooting zone. The fine root length of the trees decreased by about 35% for grevillea
and 65% for senna, because of maize competition, manual weeding, seasonal senescence or pruning regime (senna). At anthesis,
the Lrv of maize in the upper 15 cm was between 0.8 and 1.5 cm cm−3. Maize root length decreased with greater proximity to the tree rows, potentially reducing its ability to compete for soil
resources. However, the specific root length (m g−1) of maize was about twice that of the trees, so may have had a competitive uptake advantage even when tree root length was
greater. Differences in maize fine root length and biomass suggest that competition for soil resources and hence fine root
length may have been more important for maize grown with senna than grevillea.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
994.
Lin Junping Kawasaki Masako Aoki Masanori Ishizaki Hiroshi You Gang Li Ruoyu 《Mycopathologia》2000,148(2):69-72
Mitochondrial DNA (mtDNA) types based on restriction fragment length polymorphism (RFLP)patterns with HaeIII were investigated in clinical isolates of Sporothrix schenckii in China. In addition to 23 mtDNA types (Types 1–23) so far reported, a new mtDNA type (Type 24) was found in this study. Type 24 was divided into two subtypes, Subtype 24A and 24B based on RFLP with EcoRV. Sixty-seven isolates in China consisted of 58 isolates of Type 4, 5 of Type 6, 1 of Type 5, 1 of Type 20 and 2 of Type 24. Based on the phylogeny of the mtDNA types (Types 1–24) constructed by estimating sequence divergences of mtDNA, mtDNA types clustered into two groups: Group A (Types 1–3, Type 11, Types 14–19 and Types 22–23) and Group B (Types 4–10, Types 12–13,Types 20–21 and Type 24). These results suggest that mostS. schenckii isolates in China belong to Group B.This revised version was published online in October 2005 with corrections to the Cover Date. 相似文献
995.
玉米自交系遗传变异的RFLP分析 总被引:10,自引:0,他引:10
利用RFLP标记研究了13个玉米(Zca nays L.)自交系的遗传变异。从30对探针/酶组合中筛选出杂交带型清晰、稳定、重复性好的24对组合,在13个自交系中获得85个等位基因杂交片段,平均每个位点为3.3条,平均多态性指数为0.499。13个自交系之间的遗传相似系数为0.523-0.802,平均为0.649。UPGMA聚类分析表明,供试自交系共分为5个类群,分群结果与其系谱关系基本吻合;表明 相似文献
996.
997.
Uma Bhattacharyya A. K. Dasmahapatra A. K. Medda 《Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology》2000,125(4)
Different doses of vitamin B12 (0.25, 0.5, 1, 2 and 4 μg/g, injected intraperitoneally for three consecutive days) altered the activities of mitochondrial-α-glycerophosphate dehydrogenase (α-GPD) and NADP-dependent cytosolic malic enzyme (ME) in the brain of singi fish. The α-GPD activity increased at doses of 0.5, 1, 2 and 4 μg/g vitamin B12. A dose of 0.5 μg/g vitamin B12 induced less activity than higher doses. ME activity increased with 1, 2 and 4 μg/g of vitamin B12/g. The mitochondrial and cytosolic protein content remained unchanged after vitamin B12 administration. Cycloheximide treatment inhibited the vitamin B12-induced increase in α-GPD and ME activity. Thus, vitamin B12 is involved in the induction of some enzymes in fish brain. 相似文献
998.
Motoko Oarada Hiroshi Furukawa Toshiro Majima Teruo Miyazawa 《Biochimica et Biophysica Acta (BBA)/Molecular and Cell Biology of Lipids》2000,1487(1):1-14
The effect of dietary polyunsaturated fatty acids and α-tocopherol supplementation on erythrocyte lipid peroxidation and immunocompetent cells in mice was studied comparatively using seven dietary oils (15% oil/diet, w/w) including fish oil rich in eicosapentaenoic acid (EPA, 20:5, n–3) and docosahexaenoic acid (DHA, 22:6, n–3). A 43% increase in spleen weight, about twice as many spleen cells and no change in the subpopulations of spleen cells, as well as a significant depression of mitogen-induced blastogenesis of both T and B cells in the spleen were observed in mice fed fish oil for 30 days in comparison with soybean oil diet-fed mice. In the fish oil diet-fed mice, membranous lipid hydroperoxide (hydroperoxides of phosphatidylcholine and phosphatidylethanolamine) accumulation as a marker of oxidative senescence in red blood cells (RBC) was 2.7–3.5 times higher than that in mice fed soybean oil, although there was no difference in the plasma phosphatidylcholine hydroperoxide concentration. In spite of the supplementation of α-tocopherol to up to 10 times the level in the basal diet, the degeneration of spleen cells and the stimulated oxidative senescence of RBC found by the fish oil feeding could not be prevented. The results suggest that oral intake of excess polyunsaturated fatty acids, i.e. EPA and DHA, in a fish oil diet can lead to acceleration of membrane lipid peroxidation resulting in RBC senescence linked to the lowering of immune response of spleen cells, and that supplementation of α-tocopherol as antioxidant does not always effectively prevent such oxidative degeneration as observed in spleen cells and RBC in vivo. 相似文献
999.
Aluminum in lake water and in the organs of the fish Tribolodon hakonensis was investigated in Lake Usoriko (pH 3.6), Lake Inawashiroko (pH 5.0), and the Tenryu River (pH 7.7). The concentration of
total soluble aluminum in the water was 0.51 mg l−1 in Usoriko, 0.05 mg l−1 in Inawashiroko, and less than 0.01 mg l−1 in the Tenryu. The chemical forms of soluble aluminum in the acid water were characterized as Al3+, AlL2+, and AlL≦1+. More than 90% of soluble aluminum in the water of Usoriko was Al3+, whereas AlL2+ was dominant in the water of Inawashiroko. The aluminum concentration in the organs of T. hakonensis in Usoriko was 42 μg g−1 wet weight in gills, 4.2 μg g−1 in muscle, 6.9 μg g−1 in bone, 12.7 μg g−1 in liver, 6.0 μg g−1 in kidney, and 6.0 μg g−1 in intestine, indicating accumulation of aluminum in the gills. The aluminum concentration in the organs of T. hakonensis living in Inawashiroko was approximately the same, in spite of the difference in water chemistry of the two acid lakes, especially
for pH and aluminum. This suggests that aluminum accumulation might be controlled in the fish living in the acid lakes. In
contrast, the aluminum concentration in the gills of T. hakonensis from the Tenryu was 2 μg g−1.
Received: May 20, 1999 / Accepted: December 10, 1999 相似文献
1000.
幼胚长度、2,4-D浓度、光强度等对花生体细胞胚发生的影响及高效再生系统的建立 总被引:2,自引:0,他引:2
花生幼胚在含2,4-D的诱导培养基中,形成近球状的致密的胚性愈伤组织、杆状两极结构及子叶期体胚。继代培养也有体胚发生。光照明显抑制体胚发生类似于自然栽培的情况。成熟培养基中诱导体胚根、芽两极发育完全。光下,具有根、芽的体胚于再生培养基中长成小植株后移栽于盛沙土的盆中正常生长、结实。在较好的影响因素(光照、幼胚长度、激素、切分方式、接种密度)组合下,体胚发生频率达75%以上,每子叶形成体胚3个以上。该体细胞胚高效再生系统与合子胚的发育相似,是遗传转化和胚发育研究的良好系统。 相似文献