兰州银滩黄河湿地4种植物的光合特性

本研究以兰州银滩黄河湿地自然生长的千屈菜(Lythrum salicaria)、芦苇(Phragnites awstralis)、藨草(Scirpus triqueter)、菖蒲(Acorus calamus)为研究对象,对4种典型植物生长季不同阶段的光合特性及其与环境因子间的关系进行比较分析,探讨了4种植物对湿地的适应特性和机制。结果表明,1)5月11日千屈菜、芦苇的净光合速率(P_n)呈不明显的双峰曲线,藨草和菖蒲的Pn变化较为平稳,日均P_n表现为芦苇千屈菜菖蒲藨草;8月19日,千屈菜、芦苇、藨草的Pn呈双峰曲线,光合"午休"现象明显,菖蒲为单峰曲线,日均Pn表现为芦苇菖蒲千屈菜藨草。2)5月11日,光合有效辐射(PAR)、大气温度(Ta)、大气CO_2浓度(C_a)、相对湿度(RH)、蒸腾速率(T_r)、气孔导度(G_s)、胞间CO_2浓度(C_i)、水分利用效率(WUE)与4种植物P_n的日变化存在不显著、显著(P0.05)或极显著(P0.01,P0.001)的正相关关系;8月19日,PAR、C_a、T_r、G_s、WUE、土壤湿度(SM)与4种植物P_n的日变化存在不显著、显著或极显著的正相关关系;3)5月11日,PAR、C_a、T_a、RH对4种植物的P_n影响较大,是主要的环境生理影响因子;8月19日,PAR、T_r对千屈菜、藨草的Pn影响最大,PAR、WUE对芦苇、菖蒲的P_n影响较大,是主要的环境生理影响因子。尽管各因子对4种植物的光合速率均有不同影响,但PAR是对植物光合生理特性产生影响的根本原因。     

Seasonal effects on the aerobic bacterial and fungal conjunctival flora of normal thoroughbred brood mares in Florida

Objective To evaluate seasonal effects on the presence or absence of fungal and aerobic bacterial flora of the conjunctival fornix of normal Florida Thoroughbred horses. Sample population Both eyes of 100 horses. Procedure Horses with normal anterior segment ophthalmic examinations from three farms in north central Florida were included. Each animal had the ventral conjunctival fornix of each eye swabbed with sterile culturettes. Samples were taken in October, January, April, and July (1999–2000). Aerobic and fungal cultures were plated. Bacterial cultures were reviewed at 24 and 48 h. Fungal cultures were reviewed weekly for 4 weeks. Logistic regression analysis with season as a factor and age of the horse as a covariate was performed. Statistical significance was set at P < 0.01. Results Horses ranged from 3 to 24 years of age, with a median age of 9 years. Twenty‐four genera of bacteria and 35 genera of fungi were recovered. Corynebacterium sp., Staphylococcus sp., Bacillus sp. and Moraxella sp. were the bacteria most frequently isolated. Mold species, dematiaceous mold species, Chrysosporium sp., Cladosporium sp., and Aspergillus sp. were the most frequently recovered fungi. Season did not have a significant effect on the presence of microorganisms isolated for individual horses adjusted for age. Younger horses had an increased incidence of gram‐negative rods and fungal isolates. The number of bacteria and fungi isolated are not uniform across seasons. Conclusion There were no significant differences between the number or type of organisms cultured during the sampling seasons in normal Florida horses. A large range of normal bacterial and fungal flora were isolated from these horses. The number of bacteria and fungi isolated are not uniform across seasons. The likelihood of detecting an organism depends on the horses’ age.     

禾草内生固氮菌的研究现状及应用前景

植物内生固氮菌是一类重要的固氮微生物资源,其潜在的可开发利用价值越来越受重视。本文综述了禾草内生固氮菌的研究动态、种质资源多样性、侵染途径、定殖方式、作用机理及发展前景,以期为内生固氮菌的进一步开发探究提供参考。     

华北山地阳坡中生灌草植被对CO2浓度和温度变化的光合响应

利用便携式光合气体分析系统(LI-6400),从全球变化的角度分析华北山地阳坡灌草植被群落中5种具有代表性的植物光合特征对CO2浓度和温度变化的响应.结果表明:随着温度的升高,狗尾草Setaria viridis和龙牙草Agrimonia pilosa净光合速率呈明显增大趋势,在华北山地阳坡灌草群落中具有较强的竞争力,而达乌里胡枝子Lespedeza davurica的净光合速率对CO2的响应值降低,在环境温度升高的条件下不利于其光合产物的积累.     

EMA与PCR结合检测沙门氏菌方法的研究

为了建立一种快速区分样品中沙门氏菌的死细菌与活细菌的检测方法,将叠氮溴化乙锭（EMA）与PCR技术相结合。以沙门氏茵的invA为靶基因,以沙门氏菌的纯培养细胞做模板进行扩增,并进行灵敏度、特异性、曝光时间及EMA浓度试验。结果显示,灵敏度为14CFU／mL,最佳曝光时间为2min,当EMA的浓度小于18μg／mL时．EMA对活菌靶基因的扩增没有明显的抑制,而终浓度为1μg／mL的EMA,能有效抑制lxlosCFU／mL沙门氏菌死菌的扩增。EMA—PCR能有效降低沙门氏菌检测过程中的假阳性。     

Phytotoxic sites of action for molecular design of modern herbicides (Part 1): The photosynthetic electron transport system

A bird's eye review was tried to select the bio‐rational targets from known and novel plant‐specific ones for the molecular design of modern herbicides, which exhibit efficient phytotoxicity at a low‐use rate and preserve a good environment in the 21st century. In phytotoxic sites in the photosynthetic electron transport (PET) system discussed in the present article (Part 1), the generally called bleaching herbicides interfering with the biosynthesis of photosynthetic pigments, chlorophylls and carotenoids, and the biosynthesis of plastoquinone, were considered to be good models for the molecular design of modern herbicides. The PET itself was still considered as an interesting target site for new herbicides, although they need to exert their action in all green leaves of weeds to achieve herbicidal efficacy. Because these herbicides never form a tight binding with D1‐protein, their use‐rate cannot be expected to be as low as the herbicides inhibiting chlorophyll or branched amino‐acid biosynthesis. Other herbicidal targets found in chloroplasts, namely ATP and NADPH formations, have already been omitted from the worldwide biorational molecular design program of herbicides targeting the PET system.     

茄科植物内生细菌的分离及拮抗菌的筛选

从番茄和辣椒植株中共分离到9株对植物病原真菌具有拈抗作用的内生细菌。其中，来自樱桃番茄的内生细菌株系BS-1和湘研辣椒的内生细菌株系BS-4对辣椒根腐病菌等具有较强的拈抗作用，两者在植株体内均可以定殖。BS-1和BS-4均属于芽孢杆菌。     

水稻细菌性条斑病菌拮抗细菌的筛选、评价与应用研究

从江苏省南京、泰州、扬州和宿迁等地区水稻田采集水稻病叶、健叶、根围土等样品90份,分离纯化得到1173个细菌分离物,对其进行水稻细菌性条斑病菌Xanthomonasoryzaepv．oryzicola皿内抑制试验,共获得12株拮抗能力较强的细菌,其中4株拮抗细菌抑菌圈直径大于27mm。盆栽试验结果表明,12株拮抗能力较强的细菌中有4株对水稻细菌性条斑病菌防效大于50％,其中菌株Lx-1l盆栽防效达62．5％。大面积示范试验结果表明菌株Lx．11田间防效达60．2％,显著高于化学药剂20％叶枯唑的防效（51．2％和45．8％）。形态特征、理化特性和分子鉴定分析确定菌株Lx．11为解淀粉芽孢杆菌Bacillusamyloliquefaciens。     

中苜一号紫花苜蓿碳同化分配与转移速率的研究

对紫花苜蓿(Medicago sativa L.)(中苜一号)的生长条件进行控制,并在分枝期对其进行¹³C脉冲标记,收集标记后第6,12,18,24,30 d的叶、茎、根以及土壤样品,测定各样品中¹³C含量,以此来探讨苜蓿光合碳的吸收与转移。结果表明:苜蓿各组分光合产物的分配顺序为茎>叶>根;¹³C转移速率为叶>茎>根,随着时间的延长,苜蓿各组分¹³C含量逐渐减少,最终达到稳定状态;渗漏到土壤中的¹³C含量在0~10 cm土壤层显著高于10~20 cm,但10~20 cm的¹³C含量比较稳定。     

4种结缕草光合特性及叶绿素含量的比较研究

以结缕草属4个不同种为试验材料,采用叶绿素测定仪以及光合测定仪,测定4种结缕草光合特征参数以及叶绿素含量。结果表明:(1)4种结缕草叶绿素含量由大到小依次为:日本结缕草,中华结缕草,沟叶结缕草,细叶结缕草;(2)日本结缕草和沟叶结缕草的光补偿点(LCP)为40μmol/(m2.s),接近于自然光照条件下阳性植物的光补偿点30μmol/(m2.s);(3)中华结缕草和细叶结缕草的LCP较高,为80μmol/(m2.s),光饱和点(LSP)都平均为1200μmol/(m2.s);(4)4种结缕草的表观量子效率(AQY)与自然光照条件下植物的AQY(0.03~0.06 mol/mol)一致,但是中华结缕草却显著高于其他3种,因此,可初步推断结缕草为阳性、且耐荫性较强的草坪草,并且中华结缕草以其优异的表现成为亚热带地区草坪草建坪中的最佳草种。