Influence of grazing frequency and intensity on aerial and reproductive tillering in Lolium perenne L. under subtropical conditions

Abstract

Reproductive and aerial tillering dynamics in Lolium perenne L. (perennial ryegrass) was monitored for two years under grazing. Reproductive tillers were observed from winter (June) to midsummer (February) with the main period of initiation occurring in spring to early summer (August to October). For infrequent lenient grazing, reproductive tiller densities ranged from 102 (July 1993) to 1 900 (September 1993) tillers m^?2, and from 29 (June 1994) to 980 (September 1994) tillers m^?2. By contrast, simulated continuous grazing (CG) resulted in reproductive tiller densities ranging from 13 (August 1993) to 100 (October 1993) tillers m^?2, and from 25 (July 1994) to 46 (September 1994) tillers m^?2. Aerial tillers were initiated mainly during spring, and to a lesser extent autumn and winter, with no appreciable number being recorded during summer. For infrequent lenient grazing, aerial tiller densities ranged from 25 (February 1993) to 1 620 (September 1993) tillers m^?2, and from 362 (August 1994) to 1 524 (September 1994) tillers m^?2. By contrast, CG resulted in aerial tiller densities ranging from 123 (May 1993) to 14 (June 1993) tillers m^?2, and from 5 (July 1994) to 29 (May 1994) tillers m^?2. There was no indication that reproductive or aerial tillers contribute to the persistence of perennial ryegrass under the grazing frequencies and intensities tested.     

利用基因枪共转化法获得转bar与P5CS基因黑麦草

以多年生黑麦草(Lolium perenne L.)种子成熟胚为外植体进行高效诱导愈伤组织的组培条件,在此基础上用基因枪法轰击其成熟胚的愈伤组织,共转化分别携带bar基因和P5CS基因表达框架的2种质粒,经1.2‰草丁磷(Glufosinate)抗性筛选获得了转基因再生植株.经聚合酶链式反应(PCR)检测筛选到整合bar基因的株系18个,遗传转化率为0.72%,其中5个检测到P5CS,共转化效率为27.8%.     

多年生黑麦草高频再生体系的建立及优化

从外植体预处理方式、基本培养基、激素浓度等方面着手,对多年生黑麦草愈伤组织诱导、继代、不定芽分化及再生过程中的影响因素进行了研究,提高了再生频率。结果如下：切取胚端半粒种子,经75%乙醇处理1min,0.1%HgCl处理15min,在经无菌水清洗4～6次后接种方式较好;愈伤组织诱导培养基以MS＋2,4—D 8.0 mg/L（或另添加甘露醇25 g/L）为佳;愈伤组织接种于MS＋2,4—D 8.0mg/L＋甘露醇25 g/L上进行1～2次继代后于NB＋6—BA2.0 mg/L上进行分化;不定芽转接至MS＋6—BA2.0 mg/L上进行扩繁或于1/2MS＋NAA0.5mg/L＋IAA0.5mg/L上进行生根。     

Effect of grazing frequency and intensity on Lolium perenne L. pastures under subtropical conditions: Herbage quality

Abstract

The cellulase dry matter disappearance (CDMD) and herbage nitrogen (N) of Lolium perenne (perennial ryegrass) were evaluated for pastures grown under subtropical conditions for two years, under five combinations of grazing frequency and intensity, each applied in a rotational grazing system. These quality factors were also evaluated for a simulated continuous grazing (CG) system. Low frequency, low intensity grazing produced lower CDMD and herbage N levels than higher grazing frequencies and intensities. These differences were, however, generally small. Overall, levels of herbage digestibility (estimated by CDMD) and N fell within similar ranges to those observed for perennial ryegrass in temperate environments. Seasonal trends in quality were characterized by high levels during late autumn to early summer (May to October) and low levels during mid‐summer to early autumn (January to April). These data would tend to support high frequency grazing as part of the management programme for perennial ryegrass. It is cautioned, however, that for subtropical conditions in South Africa, adopting frequent grazing may reduce persistence of perennial ryegrass.     

多裂骆驼蓬水浸液对多年生黑麦草的化感作用与生理生化表现

为探讨多裂骆驼蓬(Peganum multisectum (Maxim.) Bobr.)对多年生黑麦草(Lolium perenne L.)的化感效应,采用溶液培养和盆栽土培法研究了不同浓度多裂骆驼蓬水浸液对多年生黑麦草种子萌发和幼苗生长的影响及其生理生化表现。结果表明,多裂骆驼蓬水浸液显著抑制多年生黑麦草萌发种子的α-淀粉酶和ATP酶活性及根尖细胞的有丝分裂,提高吲哚乙酸氧化酶活性,使种子萌发率和萌发指数及幼苗根长、株高和干重下降,这种抑制效应随水浸液浓度提高而增强,并与多年生黑麦草的种植密度呈负相关。在多年生黑麦草植株生长过程中浇灌多裂骆驼蓬水浸液提高了其叶片的超氧阴离子(O₂^·-)、H₂O₂和丙二醛(MDA)含量;超氧化物歧化酶(SOD)、过氧化物酶(POD)和抗坏血酸过氧化物酶(APX)活性及抗坏血酸(ASA)含量随着水浸液浓度提高先升后降,过氧化氢酶(CAT)活性升高,谷胱甘肽(GSH)含量及光合速率(Pn)、气孔导度(Gs)和蒸腾速率(Tr)降低,胞间CO₂浓度(Ci)升高。叶绿素荧光动力学资料显示,叶片初始荧光(Fo)随多裂骆驼蓬水浸液浓度提高而增加,最大荧光(Fm)、PSⅡ潜在光化学效率(Fv/Fo)、最大光化学效率(Fv/Fm)、光合电子传递量子效率(ΦPSⅡ)和光化学狡灭系数(qP)降低,非光化学狡灭系数(NPQ)先升后降,表明叶片光合机构受到伤害。     

琥珀酸黄杆菌促生机理及其对多年生黑麦草生长和抗逆性的生理调控作用

为探究琥珀酸黄杆菌(Flavobacterium succinicans)对非生物胁迫下多年生黑麦草(Lolium perenne)的缓解效应,本试验研究了菌株DSM4002的生物学特性,并在盆栽条件下,分析了干旱(维持相对含水量(30±5)％处理7 d和14 d)、低温(4℃处理3 d和7 d)和盐胁迫(150 mM...     

盐土和非盐土施氮对多花黑麦草增产改质效果差异的比较

本研究对盐土和非盐土种植多花黑麦草进行氮肥施用试验,研究施氮对不同土壤条件下多花黑麦草产量及饲用品质的影响,为提高氮肥利用效率、有效改善牧草产量品质提供依据。试验分别在江苏大丰金海农场和南京六合江苏省农业科学院试验基地进行,设置N₀(对照)、N₁(氮用量100 kg/hm²)、N₂(氮用量150 kg/hm²)和N₃(氮用量200 kg/hm²)4个处理,分别在多花黑麦草拔节期和初穗期进行刈割,测定牧草产量和饲用品质。结果表明在盐土和非盐土施用氮肥对多花黑麦草饲草品质和产量的影响存在显著差异:非盐土条件下不同施氮处理的多花黑麦草产量和饲用品质均高于盐土,其中干物质体外消化率(IVDMD),粗蛋白(CP)和非结构性碳水化合物(NSC)含量非盐土条件下高于盐土,且第1茬高于第2茬;CP含量随着施氮量的上升而升高,而NSC含量随着施氮量的上升而下降;作为NSC主要组分的淀粉在盐土条件下的含量高于非盐土;施氮组的IVDMD高于对照,但不同施氮量间差异不显著;中性洗涤纤维(NDF)含量盐土条件下高于非盐土,第2茬高于第1茬;盐土不同茬次、不同施氮处理的干物质含量(DM)均显著高于非盐土,且第2茬高于第1茬,并随着施氮量的增加而下降;非盐土条件下的牧草产量高于盐土,且第2茬高于第1茬,随着施氮量的上升而升高,N₂处理组,即氮素施用量150 kg/hm²的产量最高;但在盐土上施氮,多花黑麦草的产量增加幅度高于非盐土。     

干旱胁迫对6个坪用多年生黑麦草品种抗旱性的影响

研究6个多年生黑麦草(lolium perenne L.)品种在模拟干旱条件下相对含水量、细胞膜相对透性、游离脯氨酸、叶绿素、超氧化物歧化酶、过氧化氢酶及丙二醛含量等抗性生理生化指标的变化,并对其抗旱性进行综合评价。结果表明,抗旱性强的品种在干旱胁迫(PEG胁迫)下叶片保水力强,叶绿素含量高,游离脯氨酸维持积累时间长且累积量较高,并能保持相对较高的细胞膜完整性。经抗旱性综合评价得出,6个品种抗旱性强弱依次为:爱神特>首相>百舸>顶峰>卡特>球道。     

不同有机/无机氮添加对草原土壤氮素分配和转化特征的影响

氮沉降增加已成为全球变化的重要现象之一,已显著影响草地土壤氮素循环。以内蒙古额尔古纳草甸草原为研究对象,进行了6年不同形式氮添加试验,设置无机氮和有机氮比例分别为：10∶0 （N₁）,7∶3 （N₂）,5∶5 （N₃）,3∶7 （N₄）,0∶10 （N₅）和对照处理0∶0 （CK）。通过土壤有机质物理分组及室内矿化培养的方法,从氮素形态、氮素组分及氮素潜在矿化三方面研究不同比例有机、无机氮添加对草原土壤氮素分配和转化特征的影响。结果表明,土壤全氮含量未受氮素添加形式的影响;氮添加显著提高了0~20 cm土层矿质氮含量,尤其是土壤硝态氮,其中N₄（无机氮∶有机氮=3∶7）混合氮肥处理下硝态氮含量增幅最大,较对照处理增加1332%。不同形式氮添加没有影响氮素在土壤颗粒态有机氮（轻组）及矿物结合态有机氮（重组）中的占比;N₁（无机氮∶有机氮=10∶0）处理显著提高了0~10 cm土层颗粒态有机氮（轻组）及0~20 cm土层矿物结合态有机氮（重组）中的氮素相对含量,较对照分别增加了91%和44%。氮添加增加了10~20 cm次表层土壤硝化速率的同时降低了氨化速率,但土壤净氮矿化速率不受氮添加形式的影响。因此,有机/无机氮添加比例变化对草原土壤氮素形态和周转的影响也更加复杂。     

遮阴胁迫对麦冬和多年生黑麦草根际土壤细菌群落结构和多样性的影响

为探究麦冬（Ophiopogon japonicus（Linn.f.）Ker-Gawl.,缩写为OJ）和多年生黑麦草（Lolium perenne L.,缩写为LP）根际土壤微生物群落对遮阴胁迫的响应机制,本试验利用Illumina HiSeq2500测序平台,以16S rRNA基因为标靶进行相关研究。结果表明：遮阴改变OJ和LP土壤中硝态氮、铵态氮、全磷、全钾、速效钾和速效磷含量;遮阴显著改变OJ和LP根际土壤细菌群落组成,但是对其多样性影响不显著;OJ和LP根际土壤中变形菌门（Proteobacteria）和酸杆菌门（Acidobacteria）为主要优势菌群,相对丰度分别为26.34%~35.23%,19.79%~24.24%和19.03%~24.49%,19.20%~32.96%。遮阴导致OJ根际土壤中变形菌门、绿弯菌门（Chloroflexi）和疣微菌门（Verrucomicrobia）的丰度降低,而LP根际土壤中其相对丰度显著高于OJ。相关性分析表明：土壤速效钾、全氮是影响OJ根际土壤细菌群落结构的主要原因,而铵态氮、硝态氮、全氮是影响LP根际土壤细菌群落结构的主要原因。因此可得出,遮阴改变了OJ和LP土壤的理化性质,改变了其根际土壤中优势细菌类群组成,而植物本身对土壤细菌群落组成的影响强于遮阴胁迫。     

农牧交错带退耕还草对土壤有机质和氮的影响

在农牧交错带地区对退耕还草的草地进行土壤分析并与春小麦地比较,研究牧草对土壤有机质和氮含量的影响.结果表明,播种第2年(生产第1年),草地0～20 cm土壤有机质和全氮含量比小麦地有明显改善;单播和混播草地,播种第3年(生产第2年)较第2年土壤有机质和全氮含量均有增加,混播牧草改善土壤氮的效果比单播牧草更显著;老芒麦、无芒雀麦单播以及老芒麦 无芒雀麦混播可以明显改善土壤有机质;老芒麦 无芒雀麦、老芒麦 冰草3∶1的混播比例可以有效地增加土壤硝态氮含量.     

混播比例和施氮肥对箭筈豌豆/燕麦草地根系特性的影响

豆科和禾本科牧草混播是栽培草地的重要模式之一,能显著改善土壤,提升系统可持续生产能力。牧草根系是土壤有机质返还的重要来源,但混播草地中牧草根系特性的变化尚不清楚。以箭筈豌豆和燕麦草地为对象,研究了不同施氮肥水平和混播比例下其根生物量、根性状的变化。结果表明:1)混播比例和施氮肥对草地根生物量和根性状有显著交互作用,混播草地根生物量显著大于单播;与高氮肥处理相比,根生物量在低、中氮肥处理下更高;高氮肥对根长、比根长、根表面积和比根面积在植物生长前期表现为抑制作用,在生长后期随混播中箭筈豌豆比例的增大,抑制作用减轻。2)混播条件下土壤硝态氮含量大于单播,而土壤铵态氮含量仅在乳熟期时大于单播,且随混播中箭筈豌豆比例增大,矿质氮含量增加;施氮肥对0~30 cm土层中的矿质氮含量有显著影响,其含量在施氮肥100 kg·hm^-2下最高,不施肥下最小。3)根生物量与土壤硝态氮含量间显著正相关,根长、根表面积、根体积与土壤硝态氮含量间显著负相关。综上,混播中箭筈豌豆比例的增加有助于改善土壤矿质氮,优化混播草地根性状。     

苜蓿后茬冬小麦对氮素的响应及土壤氮素动态研究

2001至2004年,在甘肃庆阳黄土高原定位研究了施氮和不施氮对比条件下,4龄苜蓿后茬冬小麦对氮素的响应.结果表明,4龄苜蓿后茬冬小麦产量对氮连续3年有响应,至第3茬,施氮显著增加籽粒产量(P<0.05),促进了第1茬冬小麦对氮的吸收,与产量的变化趋势一致;第2茬冬小麦对氮肥的利用率最高,达47%,不施氮下土壤氮素处于亏缺状态,第1年的亏缺量最大、第2年最小;施氮明显增加第2茬冬小麦0～60 cm 土层中硝态氮的含量,且硝态氮的累积峰从2003年的0～60 cm土层,转移到2004年的60～200 cm, 表明氮有一定程度的向下淋溶.在黄土高原,4龄苜蓿后茬种植头茬作物可不施氮肥.     

Research note: Level of nitrogen fertilization and the dry matter yield of Digitaria eriantha cv. Irene in the Transvaal middleveld

Abstract

N fertilizer was applied as a single dressing in spring at 0, 20, 40, 80, 160 and 320 kg N ha^‐1 a^‐1 to an established Digitaria eriantha pasture, previously used as a hay crop. The only significant increase in dry matter (DM) yield was obtained with 80 kg ha^‐1 a^‐1. The DM production per unit of nitrogen (N) applied also reached a maximum with 80 kg N ha^‐1 a^‐1. The distribution of rainfall also influenced DM yield.     

利用方式对盐渍化土壤中有机质和盐分的影响

在河西盐渍化土地区选择了天然草地、小麦地、1年生苜蓿地、2年生苜蓿地和3年生苜蓿地,就不同利用方式对盐渍化土有机质和盐分的影响进行了研究.结果表明,种植农作物后,土壤的有机质含量明显下降;种植苜蓿后,前2年土壤有机质含量减少,3年后显著增加.土壤盐分在开垦种植后显著下降,苜蓿地的降盐效果更好.可溶性阳离子中,Mg2 含量的下降趋势最大,其变化曲线与全盐相同;Na 向土壤下层迁移,Ca2 含量随土壤深度的增加而降低, K 含量下降.     

黄土高原弃耕地植被演替及其对土壤养分动态的影响

弃耕地演替过程中植被和土壤的互动效应对于植被恢复与重建具有重要意义。本研究选择黄土高原不同演替阶段的弃耕地(弃耕时间分别为1、6、12、22年),连续2年调查各弃耕地的物种丰富度、群落地上生物量,测定0~60 cm土层的土壤容重、pH值、土壤有机质和全氮含量,分析弃耕地演替过程中群落地上生物量、土壤理化性质的变化过程和趋势以及植被土壤之间的互动效应。结果表明:1)弃耕地演替过程中,弃耕早期(1~6年)为茵陈蒿+白莲蒿的杂草群落,演替中期(6~12年)为赖草群落,演替中后期(12~22年)为无芒隐子草+短花针茅群落。随着弃耕时间的增加,物种丰富度呈先减少后增加的变化趋势,地上生物量持续增加。2)土壤有机质和土壤全氮在0~10 cm土层中最高,表现出明显的表聚效应;弃耕时间和土层深度对土壤有机质和土壤全氮产生极显著的影响,弃耕时间与土壤有机质和土壤全氮之间均表现为负相关关系,土壤有机质和土壤全氮具有较为明显的时间效应。3)群落地上生物量与弃耕时间呈显著正相关关系,与土壤有机质和土壤全氮二者之间呈负相关关系,弃耕时间对群落生物量产生正效应,土壤有机质和全氮对群落生物量产生负效应。     

Research note: A preliminary study of the root distribution of Commiphora pyracanthoides Engl. (BURSERACEAE) in the Sweet Bushveld of the Northern Province,South Africa

Abstract

The root distribution of Commiphora pyracanthoides Engl., a potential encroaching woody species in the sweet bushveld areas of the Northern Province, South Africa, was studied at the Mara Agricultural Development Centre. The root system of ten C. pyracanthoides shrubs consisted of a taproot system supported by a well developed fleshy secondary root system. Minimum branching of secondary roots occurred, resulting in the absence of tertiary and feeder roots. Weak relationships existed between root distribution, plant height and canopy diameter, but subjectively estimated, secondary roots extended horizontally at an average depth of 15 ‐20 cm to a distance of more or less 1–1.5 times the canopy diameter and 1.5–2 times tree height. It is proposed that the correct placement of soil‐applied arboricides and/or absorption mechanisms may be critical for effective chemical control of C. pyracanthoides.     

The influence of aging and low zinc nutrition on the choroid in the pig: I. The melanocyte

The effects of low zinc nutrition and aging on central choroidal melanocytes were examined in the pig. Three populations of pigs (young, pregnant and aged), were maintained on either control (C) or low zinc (LZ) diets. Twenty-five weanling boars were sacrificed at 2, 4, 8, 10, and 12-month intervals, and nine pregnant sows and eight aged sows were sacrificed after a 6-month interval. Melanocytes of the central choroid were morphologically and morphometrically examined. The melanocyte was found to be conservative in its form, which was mostly elliptical longitudinal profile, throughout the different age populations that were fed the C diet. Morphometric observations revealed that this cell type increased in size in the oldest animals, having been 40% greater than that in the younger two populations. However, the overall percentage area occupied by melanocytes remained the same throughout all age groups. In the animals that were fed the LZ diets, a large subpopulation of choroidal melanocytes was oval to round in shape in the pregnant and aged groups. Many members of this subpopulation possessed less opaque pigment than the elliptically shaped cell. Measurements of the size and percentage area occupied in these oldest groups increased significantly. In addition to the change of size, shape and melanin opaqueness, unusually large melanosomes were consistently observed in the pregnant and aged LZ groups. Low zinc nutrition had a remarkable age-related impact on the usually quiescent melanocyte.     

The influence of aging and low zinc nutrition on the choroid in the pig: II. The melanosome

The effects of low zinc nutrition and aging on central choroidal melanosomes were examined in the pig. Melanosomes of central choroidal melanocytes were morphologically and morphometrically examined in three populations of pigs (young, pregnant and aged), that were maintained on either control (C) or low zinc (LZ) diets. In C groups, the typical melanosomes decreased in size with age, although a subpopulation of larger melanosomes occurred in the oldest group. In contrast, the melanosomes of the animals on LZ diets increased in size significantly in the adult groups. The melanosomes in the pregnant and aged groups were 65% and 30–40% greater than those of the age-matched C groups. Extremely large melanosomes were frequently encountered in adult LZ choroidal melanocytes. Melanogenesis of these large bodies included the formation of one or more outer shells. Fusion of adjacent large melanosomes was also observed. Melanolysosomal-like bodies were observed, particularly among the pigmented cells in the large blood vessel region of C and LZ adults. Melanin dynamics, i.e. its production and breakdown, occurred within choroidal melanocytes throughout much of the lifespan of the pig. This dynamic was greatly influenced by low zinc nutrition, resulting in unusual and aberrant melanin activity.