栽培措施对彩色马蹄莲细菌性软腐病发生的影响

以彩色马蹄莲的红色品种(M5)和黄色品种(M13)为供试材料,研究了不同栽培基质、覆盖方式、施肥种类、施肥方法等因素对彩色马蹄莲细菌性软腐病发生的影响。研究结果表明:栽培基质的不同对细菌性软腐病的发病率影响显著,用泥炭作基质能降低发病率。栽培基质表面覆盖与否和覆盖材料的不同对细菌性软腐病的发病率高低影响较大,栽培基质表面覆盖麦草发病率最低。不同的追肥时间和肥料种类的处理显示,在营养生长时期追肥和施用高钾肥也可以有效地降低彩色马蹄莲软腐病的发生率,开花期追肥和施用氮肥则有利于彩色马蹄莲软腐病的发生。     

不同时期滴灌对紫花苜蓿种子产量及其构成因子的影响

对紫花苜蓿种子田进行了不同灌溉处理,测定了不同处理的种子产量、株高、千粒重、花序数/生殖枝、豆荚数/花序、籽粒数/豆荚等产量构成因素及发芽势、发芽率等指标.结果表明,在孕蕾-初花期灌水可形成较高苜蓿种子产量(721.8 kg·hm-2),较对照提高15.6％.不同灌水处理在株高、千粒重、结荚花序数/生殖枝、荚果数/花序...     

不同处理对瑞香狼毒种子发芽影响

研究了采集于植株上新鲜的和3℃下低温保存0.5a、1a的狼毒种子在不同温度下的发芽情况,以及鲜种在较适宜温度30℃下不同处理（即98%H2SO4浸种5min、10min、15min、20min,30﹪H2O2浸种30min、60min、90min、120min,低温层积处理,破裂种皮,120min磁场干扰16.1ht、42.1ht、61.1ht）条件下的发芽率。结果表明：狼毒种子种皮致密坚硬发芽率低,鲜种和低温保存的种子,均在30℃下发芽率最高。鲜种在30℃下,98%H2SO4和30﹪H2O2浸种对狼毒种子发芽率影响不明显,低温层积和破裂种皮发芽率显著提高,分别可以达到80%和60%且发芽时间相比对照略提前。磁场干扰,发芽时间均比对照提前,其中61.1ht影响明显,可比对照提前8d,但对发芽率影响均不明显。     

酸和热处理对膜分离牦牛乳酪蛋白功能特性的影响

选择甘肃天祝牧区的鲜牦牛乳为研究对象,采用微滤的分离方法获得牦牛乳酪蛋白,研究了在pH 6.4、6.6、6.8、7.0及80、100、120、140℃处理后牦牛乳酪蛋白的热稳定性、疏水性、粒径大小和分子质量的变化。结果表明：在pH 6.8时,不同温度处理后各个功能性质均为最差,而在远离变性温度（140℃）的条件下,酪蛋白具有良好的功能特性。在酸诱导和热处理后,蛋白质分子发生了极化,维持空间结构的疏水作用力遭到破坏,引起蛋白分子的解离或聚集,导致蛋白分子自身结构发生改变,从而影响其性质的优劣。     

Long-term impacts of prescribed burning on regional extent and incidence of wildfires—Evidence from 50 years of active fire management in SW Australian forests

Prescribed burning is advocated for the sustainable management of fire-prone ecosystems for its capacity to reduce fuel loads and mitigate large high-intensity wildfires. However, there is a lack of comprehensive field evidence on which to base predictions of the benefits of prescribed burning for meeting either wildfire hazard reduction or conservation goals. Australian eucalypt forests are among the very few forest types in the world where prescribed burning has been practised long enough and at a large enough spatial scale to quantify its effect on the incidence and extent of unplanned fires. Nevertheless even for Australian forests evidence of the effectiveness of prescribed burning remains fragmented and largely unpublished in the scientific literature.     

Beyond reduced-impact logging: Silvicultural treatments to increase growth rates of tropical trees

Use of reduced-impact logging (RIL) techniques has repeatedly been shown to reduce damage caused by logging. Unfortunately, these techniques do not necessarily ameliorate the low growth rates of many commercial species or otherwise assure recovery of the initial volume harvested during the next cutting cycle. In this study, we analyze the effect of logging and application of additional silvicultural treatments (liana cutting and girdling of competing trees) on the growth rates on trees in general and on of future crop trees (FCTs) of 24 commercial timber species. The study was carried out in a moist tropical forest in Bolivia, where we monitored twelve 27-ha plots for 4 years. Plots received one of four treatments in which logging intensity and silvicultural treatments were varied: control (no logging); normal (reduced-impact) logging; normal logging and low-intensity silviculture; and, increased logging intensity and high-intensity silviculture. Tree growth rates increased with intensity of logging and silvicultural treatments. The growth rates of FCTs of commercial species were 50–60% higher in plots that received silvicultural treatments than in the normal logging and control plots. Responses to silvicultural treatments varied among functional groups. The largest increase in growth rates was observed in FCTs belonging to the partially shade-tolerant and the shade-tolerant groups. These results indicate that silvicultural treatments, in addition to the use of RIL techniques, are more likely to result in a higher percentage of timber volume being recovered after the first cutting cycle than RIL alone.     

Inoculation treatments affect the migration and colonisation of rhizobia in alfalfa (Medicago sativa L.) plants

Purpose: The purposes of this study were to characterise the migration and the colonisation dynamics of two different fluorescent-tagged rhizobia in various alfalfa tissues (especially in seeds); and also to develop efficient inoculation treatments to promote colonisation ability of target rhizobia in elite seed varieties.

Materials and methods: Four treatments (root drench, root damaging and drench, root drench with matrine, and flower spray) were applied to inoculate alfalfa with two fluorescent-tagged rhizobia, Ensifer meliloti LZgn5f (gn5f) and Ensifer meliloti 12531f (12531f), at three different growth stages; bud, flower and pod stages. The migration and colonisation dynamics of the two fluorescent tagged rhizobia strains were monitored using UV lamp detection and a stereo fluorescence microscopy.

Results: The results showed that both rhizobia strains mainly colonised the roots and could migrate to aerial tissues. In aerial tissues, when alfalfa plants were inoculated during the bud stage, both rhizobia strains mainly colonised the leaves and stems; during the flower stage, a spray inoculation treatment resulted in more 12531f colonising reproductive tissues, while during the pod stage, more rhizobial strains gn5f colonised seeds using the root drench with matrine treatment.

Conclusions: These results indicate that endophytic rhizobia are natural inhabitants of internal regions of roots, stems, leaves and that the endophytes may arise from reproductive tissues, such as seeds. Understanding the population dynamics of endophytic rhizobia in alfalfa would considerably improve the survival of target rhizobia during seed transfer. Combining target endogenous rhizobial species with good alfalfa seed varieties may lead to the development of a novel breeding method.     

施肥、刈割对短尖苔草生理生化特征的影响

短尖苔草(Carex brevicuspis)是洞庭湖分布面积最广的植物之一,具有生物量大、营养价值高等特点,是优良的畜牧饲料资源。为探明该植物对施肥、刈割的生理响应机制,从而为开发该饲料植物提供依据,研究了该植物在不同施肥量与刈割次数条件下的生理生化变化。结果表明:随着施肥量的增加,短尖苔草可溶性蛋白含量呈现先下降后上升趋势,较对照增加140.01%;叶绿素、可溶性糖、脯氨酸、丙二醛(MDA)含量以及超氧化物歧化酶(SOD)、过氧化物酶(POD)、过氧化氢酶(CAT)活性均呈现先上升后下降的趋势。随着刈割次数的增加,短尖苔草叶绿素含量呈现下降的趋势,其降幅达21.30%;SOD活性呈现先上升后下降的趋势,可溶性蛋白含量呈现先下降后上升趋势,POD、CAT活性则呈现上升趋势。可见施肥量为20 g/m2时可促进短尖苔草光合作用,增加抗氧化酶的活性;刈割两次促进了渗透调节物质的合成,为植物恢复生长提供了生理基础。     

生长期内三种结缕草对盐胁迫的响应

试验以大穗结缕草、沟叶结缕草和日本结缕草为试材,研究了不同盐浓度(0,0.2%,0.4%,0.6%,0.8%)对生长期内3种结缕草叶片膜脂过氧化及生长的影响。结果表明,3种结缕草的生物量均随着盐浓度的增加逐渐减小;随着盐浓度的提高及处理时间的延长,3种结缕草的可溶性蛋白含量逐渐降低;相对电导率和丙二醛含量增加,在低盐浓度(0.2%~0.4%)下,两者增加幅度较小,当盐浓度为0.8%时,3种结缕草的相对电导率均达最大值,分别是38.71%,41.32%,40.97%,可溶性蛋白含量均达到最小值,分别为2.08,1.15和1.33 mg/g FW。Pro含量在处理后第10天达最大值,之后逐渐下降,后期变化比较平稳。在低盐浓度(0.2%~0.4%)下,CAT和SOD活性逐渐降低,而高盐浓度(0.6%~0.8%)下,两种酶活性呈上升-下降-上升的趋势。3种结缕草相比,大穗结缕草在高盐浓度胁迫下的相对电导率和丙二醛含量最低,而保护酶活性和可溶性蛋白含量最高。试验证明大穗结缕草抗盐能力最强,沟叶结缕草次之,日本结缕草较差。