西昌南亚热带生态区紫花苜蓿根系性状测定分析

经选择非秋眠生长特性3年生长期苜蓿作根系测定分析,得出0～30cm、30～60cm、60cm以上根系生物量两品种平均约在73∶21∶6,表明根系分层生物量与北方基本一致,根冠比平均在1.16∶1,趋于一致,表明非秋眠苜蓿品种适应南方亚热带生态区生长,并具高产潜力。

无土草坪草根系生长状况的测定与探析

用无土栽培的方式种植草坪,通过对多年生黑麦草(Lolium paenne L.)、高羊茅(Festuca arundinacea Schreb.)、紫羊茅(Festucarubia L.)、草地早熟禾(Poapratensis L.)四种草的根系生长速度的测定。得知,多年生黑麦草>高羊茅>紫羊茅>草地早熟禾。但多年生黑麦草、高羊茅和紫羊茅属弱根茎丛生草,结网抗拉能力差。草地早熟禾生长虽慢,但有根茎,结网抗拉能力强,但成网所需时间较长。因此,要达到一个理想的效果,应采用不同草种按一定比例混播。

楸树幼林根系调查研究

对楸树１～３年生幼林进行了单株根系测定。１、２、３年生林木根系的水平分布分别达９５ｃｍ、２１０ｃｍ、４１５ｃｍ；垂直分布分别达８０ｃｍ、１８０ｃｍ、２００ｃｍ。单株根系集中分布范围：１年生林木深度４０ｃｍ以上，水平６０ｃｍ见方，占根系总干重的９３．６％；２年生林木深度１００ｃｍ以上，水平１００ｃｍ见方，占９４．８％；３年生林木深度１４０ｃｍ以上，水平２２０ｃｍ见方，占９４．３％。根系含水量６２．１％～８０％，愈接近根端部位，其组织愈幼嫩。

Determination of Organic Acids in Root Exudates byHigh Performance Liquid Chromatography: III. Effectsof Interfering Factors

A solution culture experiment was conducted to investigate the effects of collection time and interferingions on separation and determination of low-molecular-weight organic acids in root exudates of soybeanusing the method for directly collecting root exudates. The suitable collection time of root exudates andthe interfering ions affecting organic acid determination were determined. The method for removing theinterfering ions was established and analyzed. The release amount of root exudates increased with theincrease of collection time from 0 to 120 min but decreased with increasing of collection time from 120 to 240min. The maximum exuding amounts of organic acids were observed in root exudates at the collection time of120 min. There was a significant difference of organic acid components between the treatments of collectiontime of 120 min and 240 min. Citric acid was found only in the treatment of 120 min collection time. NO3-was the main interfering ion in organic acid determination and had the same retention time as oxalic acid.Anion exchangs resin (SAX) properly treated by HPLC (high performance liquid chromatography) solventcould remove NO3- anion in sample solution of root exudates, thus enhancing the recoveries of organic acidsin root exudates. There was no significant effect of the chemicals added into sample solution such as H3PO4,SAX and KNO3 on the retention time of organic acids.

放牧强度和短期休牧对青藏高原东部高寒草甸优势物种根系分泌速率的影响

根系分泌物是调节土壤养分循环的关键物质,对土壤微生物生理活性和有机物分解等土壤生态过程有关键影响.为了解放牧条件下根系分泌物分泌速率和变化规律,在放牧管理试验样地上,采用原位草本根系分泌物收集法,在生长旺季测定不同放牧强度(不放牧、轻度放牧、重度放牧)和放牧停止后1 d和21 d取样(视为短期休牧)青藏高原高寒草甸优势物种垂穗披碱草(Elymus nutans)的根系分泌速率.结果显示:放牧条件下,垂穗披碱草在生长旺季正午的根系分泌平均速率(以C计)为851.29μg g^(-1) h^(-1).放牧停止后1 d,不放牧、轻度放牧和重度放牧的根系分泌速率无显著差异;而放牧停止后21 d,轻度放牧的根系分泌速率[(1 032.33±53.63)μg g^(-1) h^(-1)]和地上生物量增量显著高于不放牧,重度放牧则与不放牧差异不显著.本研究表明,轻度放牧和适当短期休牧能够增加根系分泌速率,并可能通过正反馈作用刺激植物地上补偿生长.