巨尾桉挥发物化感作用初步研究

在实验室条件下进行巨尾桉(Eucalyptus grandis×E.urophylla)新鲜桉叶和桉油的挥发物对4种受试植物种子萌发和幼苗生长的影响试验.结果表明:巨尾桉挥发物对受试植物的种子萌发和幼苗生长均有抑制作用,且抑制作用强度,桉油挥发物均显著或极显著大于桉叶自然挥发物.桉油挥发物的作用强度有明显的浓度效应,浓度增大,抑制作用增强.不同受体植物对巨尾桉挥发物化感作用的敏感性差异明显,其中甜菜心和白萝卜敏感性较强,水稻和热研2号柱花草敏感性则较弱.     

刚果12号桉叶片水抽提物对4种植物幼苗生长的影响

采用盆栽法研究了刚果12号桉叶片水抽提物在水分胁迫（水渍与干旱）和养分缺乏与丰足的环境条件下对4种植物生长的影响。结果表明，植物种类与盆栽基质的肥力是影响植物幼苗生长的关键因素，而桉叶水抽提物与土壤水分对植物幼苗的生长虽有影响，但与前二相比作用较小。因此，在退化的桉树人工林地重建林下植被，首先应选择耐瘠薄、耐旱性强和对化感作用不敏感的植物，如柱花草等豆科植物，既能自身固氮，又能通过循环增加土壤养分，当然应该注意豆科与禾本科搭配。结果还表明，在逆境条件下，桉树的化感作用会增强，并与其它因素互相作用，抑制林下植被生长。     

南瓜根系及根部土壤水浸液化感作用研究

以黄瓜、西瓜作受体材料,研究南瓜根系及根部土壤水浸液的化感作用。结果表明,南瓜根系及根部土壤水浸液对受体种子萌发率、萌发指数、幼苗根长、苗高和苗干重存在化感促进或抑制效应。对指标进行综合效应分析,发现南瓜根系及根部土壤水浸液化感作用呈现浓度效应及受体差异性,一定浓度水浸液处理对受体种子萌发阶段、幼苗生长阶段及整体生长有促进作用,但西瓜较黄瓜对浓度敏感,0.02 g/mL南瓜根系及根部土壤水浸液对黄瓜化感促进强度最大,0.04 g/mL处理下,表现为化感促进强度降低或微弱抑制作用;0.02和0.04 g/mL南瓜根系水浸液及0.04 g/mL根部土壤水浸液对西瓜则表现为强烈抑制现象。     

空心莲子草浸提液对苏丹草根缘细胞的化感作用

采用悬空气培养法研究了入侵植物空心莲子草(Alternanthera phiLoxeroides Griseb)不同器官水浸提液对苏丹草根尖生长、根缘细胞活性和根冠果胶甲基酯酶(PME)的化感效应。结果表明:空心莲子草水溶性化感物质对苏丹草根尖的发育有明显的抑制及伤害作用,且随着处理浓度增加抑制作用显著增强;苏丹草根缘细胞存活率随着水浸提液浓度的升高而下降;苏丹草根冠果胶甲基酯酶(PME)活性与水浸提液处理浓度具有密切相关性,呈先上升后下降趋势(茎例外),经茎的水浸提液处理的苏丹草根冠PME活性则表现出与空心莲子草根、根状茎和叶相反的趋势;空心莲子草不同器官化感作用差异显著,其综合化感效应表现为:叶>根和根状茎>茎。化感作用是空心莲子草实现干扰性竞争的基础,也是排挤和绞杀土著物种迅速占领生态位的主要原因之一。     

巨尾桉小枝、叶片水浸提液对三种蔬菜种子发芽的影响

为了解巨尾桉小枝、叶片内含物对三种蔬菜种子萌发的化感作用,分别用巨尾桉新鲜叶片、小枝的水浸提液供水做萝卜、甘蓝和油青菜心种子的发芽试验,结果表明：新鲜叶片、小枝水浸提液会强烈地抑制三种供试种子的萌发和胚根的生长。对三种供试种子萌发的抑制作用叶片浸提液大于小枝浸提液。     

黄顶菊水浸提液对小麦幼苗的生理效应

为了解黄顶菊对小麦的化感效应,研究了黄顶菊茎叶、根水浸提液对小麦根系活力、叶片细胞膜透性和抗氧化特性的影响。结果表明,随提取液质量分数的提高,小麦根系活力、SOD、POD及CAT活性逐渐降低,而叶片细胞膜透性、MDA的含量逐渐上升。从化感效应指数RI和化感综合效应指数SE比较来看,黄顶菊茎叶对小麦的化感抑制效应大于根浸提液。     

苎麻根际土壤水浸提液对拟南芥幼苗生长的化感效应

通过种子萌发实验研究了不同浓度(0、1、2、10 mL/皿)不同苎麻品种根际土壤水浸液对模式植物拟南芥幼苗生长的化感效应,并运用相对实时定量PCR(QPCR)技术从基因水平探讨了不同浓度根际土壤水浸提液处理后与拟南芥生长素合成相关基因YUC1(AT4G32540)的表达。结果表明,随着苎麻根际土壤水浸液浓度的升高,拟南芥幼苗在中苎1号根际土壤处理下其根长与对照相比均呈现出抑制效应,在湘苎7号根际土壤处理下其根长与对照相比呈现出低促高抑现象。在中苎1号根际土壤处理下拟南芥幼苗丙二醛(MDA)含量随着苎麻根际土壤水浸提液浓度升高而上升,在湘苎7号根际土壤处理下拟南芥幼苗丙二醛(MDA)含量在低浓度时,与对照相比降低,当浓度升高,其含量呈现出升高趋势。在不同浓度根际土壤水浸提液处理下,拟南芥幼苗的过氧化物歧化酶(SOD)活性均表现为随处理浓度升高,SOD活性下降,且在中苎1号处理下,下降幅度较湘苎7号大。QPCR检测结果表明,2个苎麻品种处理下YUC1其基因的表达量随水浸提液浓度增加均降低,且中苎1号下降幅度较湘苎7号大。可见,随浸提液浓度升高,苎麻对拟南芥生长的化感胁迫性增强。     

假臭草水浸提液化感作用研究

以小白菜(Brassica campestris L.ssp.Pekinensis(Lour.)Olsson),萝卜(Raphanus sativus L.),水稻(Oryzasativa L.),热研2号柱花草(Stylosanthes guianensis cv.Reyan No.2)作为测试植物,研究新鲜假臭草(Praxelisclematidea(Griseb.)King and Robinson)水浸提液对种子发芽,新鲜假臭草和风干假臭草水浸提液对幼苗早期生长的化感效应以及不同生长环境下的假臭草浸提液对萝卜幼苗早期生长的化感作用。结果表明:新鲜假臭草浸提液对4种测试植物的种子发芽都有抑制作用。假臭草叶和完整植株水浸提液的化感作用明显大于其它器官水浸提液化感作用,叶可能是假臭草释放化感物质的主要器官。风干和新鲜假臭草水浸提液在低浓度时抑制所有测试植物幼苗根系生长。在逆境(如干旱和养分胁迫)中,假臭草会释放更多的化感物质,从而导致其化感作用增强。     

高粱不同组织浸提液对小麦幼苗的化感作用

为了给小麦合理轮作倒茬提供参考依据,研究了高粱不同组织的水浸提液对小麦幼苗生长的化感作用.结果表明,高粱秆、穗、叶的水浸提液对小麦幼苗的苗高和根长均有极强的化感作用,浸提液在低浓度时促进小麦生长,高浓度抑制小麦生长,且对根的化感作用大于对地上部的化感作用.高浓度高粱浸提液降低了小麦的根系活力和叶片可溶性蛋白含量,提高了小麦叶片的丙二醛(MDA)含量;小麦叶片的超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)等酶活性均显著下降.综合来看,高粱不同组织水浸提液对小麦的化感作用表现为秆＞穗＞叶.     

稻壳水浸提液对小麦及其伴生植物生长与生理的影响

为明确稻壳水浸提液对小麦(Triticu maestivum L.)和小麦田伴生植物大巢菜(Vicia sativa L.)、日本看麦娘(Aloecurus japonicus Steud.)生长与生理的影响,采用室内培养皿法分别研究了水稻稻壳水浸提液对小麦及其伴生植物苗高、苗鲜重、根长、根鲜重、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性以及丙二醛(MDA)含量等指标的影响。结果表明,0.040 g/m L以上浓度水稻稻壳水浸提液处理后,小麦苗高、苗鲜重、根长、根鲜重受到显著抑制,日本看麦娘根长、大巢菜地上部分生长受到明显抑制。稻壳水浸提液胁迫下3种受试植物叶片POD活性与MDA含量均呈逐渐上升趋势,而SOD活性呈逐渐下降趋势,它们共同作用,加速了受试植物叶片的衰老。据此认为稻壳水浸液具有一定的化感作用,其对小麦及其伴生植物的影响将有助于稻壳资源的开发和利用。     

锰对大豆氮代谢相关指标及产量品质的影响

以大豆品种垦农4号为材料,在大田小区试验的条件下,研究EDTA-Mn浸种和在初花期（R1期）叶面喷施对大豆叶片可溶性蛋白、硝态氮、游离氨基酸含量、硝酸还原酶活性及产量品质的影响。结果表明,无论在浸种处理（A）还是叶面喷施处理（B）中,中浓度锰(即A3 1.54g/L和B3 20g/L)处理对大豆叶片可溶性蛋白、硝态氮、游离氨基酸含量及硝酸还原酶活性均有一定的促进作用,但随着生育期的推进,浸种处理对各指标影响效果逐渐减弱。同时,中浓度的锰处理有利于大豆单株粒数、荚数和单株产量的提高,从而达到大豆增产的目的,且能够使大豆的蛋脂总量明显提高。高浓度的锰(即A4 15.4g/L或B4 60g/L)处理则对上述指标起抑制作用。     

新老大豆品种叶片光合特性的比较

为了了解大豆品种叶片光合特性与产量的关系，我们对跨越70多年的4个老大豆[Glycine max(L.)Merr.]品种和4个新大豆品种的光合特性和产量进行了研究。研究结果表明：新品种产量比老品种提高了91%，新品种叶片净光合速率、气孔导度、蒸腾速率、水分利用效率、叶绿素含量和比叶重也不同程度高于老品种，其中以净光合速率增加最多(17.3%)，而胞间CO2浓度却低于老品种。在盛花期和盛荚期，新老大豆品种叶片净光合速率与产量呈显著正相关（P﹤0.05），而其它光合特性指标与产量的相关性不稳定。     

The effect of sward structure as influenced by ryegrass genotype on bite dimensions and short-term intake rate by dairy cows

Abstract The effects of genotypic variation in ryegrasses on sward structure, bite dimensions and intake rate by dairy cows were investigated. Two experiments were conducted. In Experiment 1, swards were in a vegetative state whereas, in Experiment 2, they were partly reproductive and were taller with higher herbage mass but lower leaf proportion than in Experiment 1. Applicability of relationships between sward structure and bite characteristics, previously established from artificial or hand‐constructed swards, to field conditions were tested. Additional short‐term intake rates and/or sward structural characteristics were considered as indicators of potential intake for use in protocols for the evaluation of grass varieties. Four cultivars were studied: AberElan, Twins (diploid and tetraploid perennial ryegrasses respectively), Polly, a hybrid ryegrass (perennial × Italian ryegrass) and Multimo (Italian ryegrass), each established in 200‐m² plots in four replicated blocks. Herbage intake rate was determined by short‐term liveweight change (taking account of insensible weight loss) using 16 dairy cows allocated to four balanced groups with each plot grazed by one group for a 1‐h assessment period. One block was grazed per day, over a 4‐d experimental period, with each group grazing each variety in a complete crossover design. Sward characteristics and bite rate were also measured in both experiments. Bite dimensions were subsequently estimated, with bite depth being determined as a function of extended tiller height (ETH) in both experiments. Within both experiments, bite mass and intake rate did not differ significantly between swards of different cultivars despite swards containing Multimo generally having a higher ETH and water‐soluble carbohydrate concentration and lower green leaf mass, sward bulk density and neutral‐detergent fibre concentration than the other swards. However, bite depth was significantly higher (P < 0·01) in swards containing Multimo swards than in the others and, in Experiment 1, bite depth, as a proportion of ETH, was higher in swards containing Multimo and lower in those containing Twins than in the other two cultivars, whereas there was no difference in Experiment 2. Taking both experiments together, the mean bite depth was 0·5 of ETH with sward bulk density accounting for almost half the variance in the relationship between bite depth and ETH. The bulk density of the bite (bite mass per unit bite volume), measured in Experiment 2, followed a similar pattern to sward bulk density, increasing in the order Multimo, Polly, AberElan and Twins. It is concluded that the relationships between sward characteristics and bite dimensions, derived from artificial swards, are applicable to field swards, although the range in natural ryegrass sward characteristics is usually not as wide as in experiments using artificial swards. Lack of precision in the measurement of short‐term intake and in sward‐based measurements is likely to preclude their use in the evaluation of grass varieties.