Occurrence and correlations of nematodes,Fusarium oxysporum and edaphic factors on banana plantations

Problems caused by nematodes and Fusarium wilt (Panama disease) on banana plantations are responsible for yield losses and are limiting to its cultivation. In the state of Goias, there is little information about the nematode occurence on this crop, and its relation with the incidence of Fusarium oxysporum f.sp. cubense (Foc). This research had the purpose to identify the occurrence of plant‐parasitic nematodes on banana plantations and to verify its correlation with the Fusarium wilt and with the soil attributes (pH, texture, nutrients). Twelve banana orchards in the state of Goias were sampled in the municipalities of Anapolis, Caiaponia, Goiatuba, Itaguaru, Itumbiara (two areas), Jatai, Morrinhos, Ouro Verde, Palestina, Taquaral and Uruana. All sampled areas, except Morrinhos, revealed contamination with Foc, and all areas had different genera of nematodes either in the soil or in the roots samples. Meloidogyne sp., Helicotylenchus sp. and Rotylenchus sp. were the main genera of plant‐parasitic nematodes found in the samples, with Meloidogyne sp. and Rotylenchus sp. being the most dominant and abundant genera. The presence of Pratylenchus sp. increases the population levels of F. oxysporum. Helicotylenchus sp. is highly correlated with high concentrations of Mn. High population density of Meloidogyne sp. was found in irrigated areas with low concentrations of P, Ca, Mg and soil pH.     

Effects of atmospheric CO2 enrichment and root restriction on leaf gas exchange and growth of banana (Musa)

The effects of atmospheric CO₂ enrichment and root restriction on photosynthetic characteristics and growth of banana (Musa sp. AAA cv. Gros Michel) plants were investigated. Plants were grown aeroponically in root chambers in controlled environment glasshouse rooms at CO₂ concentrations of 350 or 1 000 μmol CO₂ mol^-1. At each CO₂ concentration, plants were grown in large (2001) root chambers that did not restrict root growth or in small (20 1) root chambers that restricted root growth. Plants grown at 350 μmol CO₂ mol^-1 generally had a higher carboxylation efficiency than plants grown at 1 000 μmol CO₂ mol^-1 although actual net CO₂ assimilation (A) was higher at the higher ambient CO₂ concentration due to increased intercellular CO₂ concentrations (C_i resulting from CO₂ enrichment. Thus, plants grown at 1 000 μmol CO₂ mol^-1 accumulated more leaf area and dry weight than plants grown at 350 μmol CO₂ mol^-1. Plants grown in the large root chambers were more photosynthetically efficient than plants grown in the small root chambers. At 350 μmol CO₂ mol^-1, leaf area and dry weights of plant organs were generally greater for plants in the large root chambers compared to those in the small root chambers. Atmospheric CO₂ enrichment may have compensated for the effects of root restriction on plant growth since at 1 000 μmol CO₂ mol^-1 there was generally no effect of root chamber size on plant dry weight.     

Embryogenic cell suspensions from the male flower of Musa AAA cv. Grand nain

There are very few reports on the establishment of long-term embryogenic cell cultures of banana, especially of triploid cultivars of commercial interest. Embryogenic cell suspensions were prepared using the cultivar Grand nain, the most widely grown dessert banana in the world. After culture for 5 or 6 months of immature male flowerbuds adjacent to the floral apex, yellow, compact calluses and white, friable embryogenic tissues were induced. Suspension cultures were initiated from embryogenic tissues placed in liquid medium. The packed cell volume (PCV) of the suspensions increased 2- to 5- fold with each monthly culture cycle. Plating of the embryogenic suspensions resulted in approximately 370×10³ embryos per ml of PCV. Depending on the size of embryos, 3 to 20% germination was observed. A histological survey of cell suspensions and embryo development was carried out. Cellular aggregates with cells displaying typical embryogenic features were formed. Most of the somatic embryos were probably of unicellular origin.     

Interactions between the root-knot nematode Meloidogyne incognita and Glomus mosseae in banana

The effects of the interaction between the arbuscular mycorrhizal fungus Glomus mosseae and the root-knot nematode Meloidogyne incognita on growth and nutrition of micropropagated ;Grand Naine banana (Musa AAA) cultivar was studied under greenhouse conditions. Inoculation with two G. mosseae isolates significantly increased growth of plants in relation to non-mycorrhizal plants. Response to mycorrhizae was as effective as with an optimum P fertilization in promoting plant development for most growth parameters. Meloidogyne incognita had no apparent effect on the percentage of root colonization in mycorrhizal plants. In contrast, G. mosseae suppressed root galling and nematode buildup in the roots. The percentage of mycorrhizal colonization was high (over 80%) in low P fertilized plants, but optimum P rates for bananas (four times higher than low P) significantly reduced mycorrhizal colonization. Most elements were within sufficiency levels for banana with exception of N which was low for all treatments. Mycorrhizal plants fertilized with a low P rate showed higher N, P, K, Ca, and Mg contents as compared to non-mycorrhizal plants low in P with or without the nematode. Inoculation with G. mosseae favours growth of banana plants by enhancing plant nutrition and by suppressing nematode reproduction and galling during the early stages of plant development.     

广东中部两种常见灌木的生态学比较

 通过对广东中部的阳生性灌木桃金娘和阴生性灌木九节的形态学、解剖学、植物生态学以及植物生理学等方面的比较发现：处于强光照下的桃金娘通过大的根系、多的枝叶和小的叶片在水分和养分竞争中处于优势,并利用小的枝角和叶毛来避免强光的伤害,而九节则是通过其叶、枝的最经济数量和最佳位置排列来充分利用阴暗不足的光线;桃金娘通过叶片和栅栏组织厚度以及短的小脉间距在强光下能继续进行光合作用并尽快运出光合产物,而九节的叶片则可充分利用森林底层有限的光照;在南亚热带,30％左右的透光率是林下耐荫性树种九节入侵和阳生性灌木桃金娘消亡的辐射条件;九节的生态对策为K对策,而桃金娘遵循r对策;九节和桃金娘的平均光合速率分别为5.9±1.6μmol CO2·m-2·s-1和11.9±0.4μmol CO2·m-2·s-1,光补偿点分别为0.005和0.012mmol·m-2·s-1,光饱和点分别为0.04和0.39μmol CO2·m-2·s-1,气孔传导率分别为0.053±0.037μmolCO2·m-2·s-1和0.101±0.013 mol·m-2·s-l,暗呼吸速率分别为0.42±0.0lμmol CO2·m-2·s-1和0.16±0.15μmolCO2·m-2·s-1,这些生理学差异、形态解剖学差异等与其生境差异有密切的关系。     

四种单宁植物形成层的活动周期和次生韧皮部的季节变化

余甘子Ｐｈｙｌｌａｎｔｈｕｓｅｍｂｌｉｃａ．Ｌ杨梅Ｍｙｒｉｃａｒｕｂｒａ（Ｌｏｕｒ）．Ｓｉｅｂ．ｅｔＺｕｃｃ,黑荆树ＡｃａｃｉａｍｅａｒｓｉｉＤｅＷｉｌｄｅ形成层的活动有明显的季节性,形成层活动期分别为５～１１月,３～１２月,２～１０月,其他时间休眠,细枝木麻黄ＣｗａｓｕａｒｉｎａｃｕｎｎｉｎｇｈａｉａｎａＭｉｑ的形成层周年都在活动１,２月的材料中也见到成膜林,４种树木在冬季都保留相当数量的具功能     

天然落葵红色素研究初报

落葵紅色素系以成熟的落葵果实为原料,经由物理方法提取获得的一种水溶性天然食用红色素。该色素在酸性至中性的介质中呈鲜艳的紫红色;经毒理学实验和卫生学检验,证明它是一种安全无毒,符合一般食品添加剂卫生学要求的良好的食品着色剂。据实验结果分析,落葵红色素中主要化学成分是甜菜花青素(betacyanines):甜菜苷(betanin)。     

Non-stomatal limitation of CO2 assimilation in three tree species during natural drought conditions

The effect of drought on CO₂ assimilation and leaf conductance was studied in three northern hardwood species: Quercus rubra L., Acer rubrum L. and Populus grandidentata Michx. Leaf gas exchange characteristics at two CO₂ levels (320 and 620 μl I⁻¹) and temperatures from 20 to 35°C were measured at the end of a dry period and shortly after 10 cm of rainfall. The effects of drought varied with species, temperature and CO₂ level. Calculated values of internal CO₂ concentration showed little or no decline during drought. Differences in assimilation, before vs after the rains, were most apparent at the higher CO₂ level. These latter two observations indicate nonstomatal disruption of CO₂ assimilation during the dry period. In P. grandidentata there was a substantial interaction between drought and temperature, with a resultant shift in the temperature for maximum assimilation to lower temperatures during drought. During drought, internal CO₂ concentrations increased sharply in all three species under the combined conditions of high temperatures and the higher CO₂ level.     

Some properties of polysaccharides of microorganisms from degraded straw

Extracellular polysachcarides from bacteria and yeasts isolated from decomposed straw contained various proportions of d-galactose, d-glucose, d-mannose, uronic acid, d-xylose, l-fucose and l-rhamnose. Molecular weights of the polymers determined by viscometry and gel filtration were in the range 40 000–1800 000. All the polysaccharides stabilized aggregates of volcanic ash and most were more effective than the polysaccharide from Lipomyces starkeyi. Effectiveness seemed to be more related to molecular weight than to chemical composition.