贵州山区3种木本植物无机碳利用特性的比较

以生长在喀斯特高原地区玉舍国家森林公园内的成熟银鹊树(Tapiscia sinensis)、白栎(Quercus fabri)和亮叶桦(Betula luminifera)为实验材料,通过对光合作用、叶绿素含量、叶绿素荧光参数、羧化效率(CE)、呼吸速率(Resp)、碳酸酐酶活性(WA)以及稳定碳同位素组成(δ13 C)等指标的测定,分析3种植物不同的无机碳利用特性,为该区生态环境修复选择合适的建群植物种提供依据。结果显示:(1)银鹊树、白栎和亮叶桦分布都较为广泛,银鹊树生长的最佳土壤pH是4.5~5.5,而白栎更倾向于中性到弱酸性土壤,肥沃的酸性土壤则更有益亮叶桦生长;白栎和亮叶桦都能忍受干旱和贫瘠,但是银鹊树不能忍受干旱和高温。(2)银鹊树叶片的Pn、Tr和Gs显著大于白栎和亮叶桦,亮叶桦和白栎的Pn、Tr和Gs分别是银鹊树的69.5%、48.2%、66.7%和28.6%、21.7%、22.2%;亮叶桦叶绿素含量均为银鹊树和白栎的2倍,但3种植物间的WUE则无显著差异。(3)3个树种叶片净光合速率均随着CO2浓度升高呈持续上升的趋势,但它们之间的CO2补偿点和饱和点明显不同。其中,银鹊树和亮叶桦的CO2补偿点均低于50μmol·mol-1,而白栎的则在250~300μmol·mol-1之间;银鹊树的CO2饱和点在1 200μmol·mol-1左右,亮叶桦则在2 300μmol·mol-1左右,而白栎的CO2饱和点明显高于2 300μmol·mol-1。(4)3个树种的CE、Resp和WA均为银鹊树>亮叶桦>白栎;而δ13 C值则以银鹊树最低,亮叶桦和白栎较高。其中,白栎和亮叶桦的CE、Resp、WA分别为银鹊树的5.1%、25.7%、4.0%和45.3%、54.6%、6.8%,且树种间差异显著;白栎和亮叶桦的δ13 C值显著高于银鹊树。研究表明,银鹊树能够吸收大气中的CO2或者在高活性碳酸酐酶作用下转化利用细胞内的HCO3-,它拥有较高的CO2利用能力及无机碳同化效率,因而能够拥有较高的产能;亮叶桦只能获取大气中的CO2作为无机碳源,但它对CO2的利用能力也较高,其产能仅次于银鹊树;白栎同样只能获取大气中的CO2作为无机碳源,同时它对大气中CO2的捕获、利用能力均低于银鹊树和亮叶桦,因而白栎生长非常缓慢,造成其本身对无机碳的需求也最低,所以其产能最低。     

Seed Coat Retention and Hypocotyl Hook Development in Mutants of Arabidopsis thaliana L.

Germination and growth of wild-type and two mutant strains (aux-1and Dwf) of Arabidopsis thaliana L. have been examined. Seedlingsof aux-1 exhibit agravitropic roots whereas Dwf display bothagravitropic roots and shoots. Wild-type seedlings retained the seed coat at the root-hypocotyltransition zone and developed hypocotyl hooks. In contrast,aux-I and Dwf seedlings did not retain their seed coats andlacked hypocotyl hooks. A positive gravitropic response of theroots was essential for the retention of the seed coat at theroot—hypocotyl transition zone by the attachment of roothairs to the seed coat. The development of the hypocotyl hookwas aided by the retention of the seed coat. The apical regionof the hypocotyl apparently remained agravitropic during formationand maintenance of the hypocotyl hook. Arabidopsis thaliana L., auxins, gravitropism, hypocotyl hook, mutants, peg formation, germination     

Morphological variation in Polydora ciliata complex (Polychaeta: Annelida)

Intraspecific variation in Polydora ciliata (Johnston) was assessed on the basis of evidence from morphological characters, which were studied by scanning electron microscopy. Differences were observed between populations of P. ciliata with respect to the setae of the fifth modified segment and in the caruncle. Two other species, namely P. ligni Webster and P. limicola (Annenkova), were also studied in order to assess interspecific variation. The two forms of P. ciliata , that is boring and non-boring, were found to be different morphologically.     

CHANGES IN PROTEIN BIOSYNTHESIS DURING GIBBERELLIC ACID INDUCED INDUCTION AND FORMATION OF ANTHERIDIUM IN THE FERN ANEMIA PHYLLITIDIS

Changes in protein biosynthesis have been studied during the induction and formation of antheridium in Anemia phyllitidis .
Based on incorporation of ¹⁴C-amino acid mixture into TCA precipitable material two distinct phases of accelerated protein biosynthesis were observed. First phase initiates at 4th day, while the second at 8th day of development. The first phase is likely associated with antheridium induction and second with spermatogenesis. From electrophoretic pattern of proteins on stained acrylamid gels and from radioactivity profiles of labelled proteins distinct quantitative differences between vegetative and reproductive prothalli were observed at different stages of antheridial development. Radioactivity profiles reveal characteristic pattern of each stage of antheridial differentiation.     

Germination of sclerotia of Botrytis tulipae, the cause of tulip fire

Sclerotia of Botrytis tulipae (Lib) Lind. buried in field soil germinated mainly in winter and early spring to produce conidiophores and conidia and then decayed. Except when buried very late in the year sclerotia germinated and decayed in the season following burial. In the laboratory, sclerotia from pure culture germinated in two ways. On sterile water-agar they formed colourless mycelium but no conidiophores; the rate of germination was greatest at 25 d?C. On unsterile filter paper and on soil they produced mainly conidiophores and conidia; the rate of germination was greatest at 5 d?C and was enhanced by previous cold treatment. It was unaffected by soil-moisture or pH. Primary infections of tulips arose from sclerotia placed in the soil but only when they were close to the shoot tip or developing stem. It is suggested that, because of their limited survival, soil-borne sclerotia are of importance only when tulips are planted in annual succession.     

Testing the viability of fungal sclerotia

Simple methods for producing, handling and testing the viability of sclerotia were used on five fungi, three of which produced sclerotia freely in sand-maizemeal cultures; the other two did not, and were grown on agar. After air drying, which did not affect viability, sclerotia were buried in the field in bags of nylon fabric. After recovery from soil they were surface-sterilized with calcium hypochlorite and plated on a medium containing chloramphenicol and streptomycin sulphate. Some fungi, particularly those having basidiomycete affinities, are sensitive to high concentrations of chloramphenicol.