‘MaxClover’ grazing experiment: I. Annual yields,botanical composition and growth rates of six dryland pastures over nine years

Six dryland pastures were established at Lincoln University, Canterbury, New Zealand, in February 2002. Production and persistence of cocksfoot pastures established with subterranean, balansa, white or Caucasian clovers, and a perennial ryegrass‐white clover control and a lucerne monoculture were monitored for nine years. Total annual dry‐matter (10.0–18·5 t DM ha^?1) and sown legume yields from the lucerne monoculture exceeded those from the grass‐based pastures in all but one year. The lowest lucerne yield (10 t ha^?1 yr^?1) occurred in Year 4, when spring snow caused ungrazed lucerne to lodge and senesce. Cocksfoot with subterranean clover was the most productive grass‐based pasture. Yields were 8·7–13·0 t DM ha^?1 annually. Subterranean clover yields were 2·4–3·7 t ha^?1 in six of the nine years which represented 26–32% of total annual production. In all cocksfoot‐based pastures, the contribution of sown pasture components decreased at a rate equivalent to 3·3 ± 0·05% per year (R² = 0·83) and sown components accounted for 65% of total yield in Year 9. In contrast, sown components represented only 13% of total yield in the ryegrass‐white clover pastures in Year 9, and their contribution declined at 10·1 ± 0·9% per year (R² = 0·94). By Year 9, 79% of the 6.6 t ha^?1 produced from the ryegrass‐white clover pasture was from unsown species and 7% was dead material. For maximum production and persistence, dryland farmers on 450–780 mm yr^?1 rainfall should grow lucerne or cocksfoot‐subterranean clover pastures in preference to ryegrass and white clover. Inclusion of white clover as a secondary legume component to sub clover would offer opportunities to respond to unpredictable summer rainfall after sub clover has set seed.     

不同播种方式对岷山红三叶草产量的影响

通过在海拔2 450 m的岷县南部高寒阴湿地区进行岷山红三叶Trifolium pratense cv.Minshan干草丰产栽培试验,得到以下结论：条播为岷山红三叶进行干草生产的最佳播种方式,行距以20 cm最为理想,该行距下生长速度快,而且产草量最高。播种当年A组（行距20 cm）鲜草产量比对照组(撒播)高出4 987.5 kg/hm2,是对照组的1.27倍,差异极显著（P＜0.01）;A组鲜草产量比B组（行距40 cm）高101 kg/hm2,差异显著（P<0.05）。生长第2年,A组鲜草产量均高于对照组和B组,是对照组的1.16倍,差异极显著（P＜0.01）,是B组的1.02倍,差异显著（P＜0.05）。不同播种方式对岷山红三叶鲜干比无影响。     

盐胁迫对白三叶种子萌发及幼苗生长的影响

研究盐胁迫对白三叶种子抗盐萌发和幼苗生长的影响,结果表明:不同浓度的NaCl胁迫下,白三叶种子的发芽势、发芽率、株高均呈下降趋势,处理和对照之间的差异达到极显著水平;盐胁迫对白三叶叶片的叶绿素含量和根系活力均有一定的影响,叶绿素含量对照与处理之间差异达到极显著水平,根系活力对照与低浓度处理差异不显著,与高浓度处理之间达到极显著水平。     

种间互作对苹果/白三叶复合系统根系生长及分布的影响

设置苹果(Malus demestica Borkh)和白三叶(Trifolium repens L.)单作与间作栽培处理,通过根箱试验研究种间互作对苹果、白三叶根系生长及其分布的影响。结果表明:种间互作导致苹果根系生长发育的正效应和白三叶根系生长发育的负效应;苹果、白三叶不同径级根系对种间互作的响应能力不同,细根比粗根表现出较强的可塑性;苹果细根占总根中的比例提高,而白三叶细根占总根中的比例则降低;种间互作对苹果、白三叶不同径级根垂直分布格局影响不明显,但对不同径级根在各土层中的分布比例产生了明显影响,苹果粗根和细根均有下移的趋势,细根下移的趋势更明显,而白三叶细根分布有上移的趋势,粗根则无明显变化。总之,种间互作对苹果、白三叶根系生长发育及其垂直分布产生了一定的影响,对不同径级根生长及其垂直分布的影响不同。     

不同温度对白三叶种子发芽及幼苗生长的影响

试验研究了温度对白三叶(Trifolum repens L.)种子发芽及幼苗生长的影响.结果表明,温度过高或过低,对白三叶发芽及幼苗生长情况均会产生影响.温度为25%时,白三叶种子的发芽速度、发芽率和发芽势最好,株高和地上部的生物量也是最大值;当温度升高至30℃时,发芽速度显著降低,发芽势有所下降,而发芽率、株高和地上部生物量与25%处理下无显著差异;温度低至15℃时,发芽率、发芽势、株高和地上部生物量显著下降,发芽速度与25℃处理下无显著差异.     

遮阴强度对西南地区野生马蹄金生理特性的影响

以5份西南地区野生马蹄金(Dichondra repens J.R.Forst.＆G.Forst)为材料,1份美国引进的品种普通马蹄金为参照,在4个光照梯度下(遮阴0、遮阴30%、遮阴50%、遮阴70%)进行耐阴性研究,测定其叶片相对电导率、游离脯氧酸、MDA和可溶性糖含量等生理指标.结果表明,参试的5份西南地区马蹄金材料中,小哨(YD200503)、壁山(SD200411)、纳溪(SD200310)的耐阴性较差,兰田(SD200309)和三都(GD200503)的耐阴性较强.     

红车轴草总黄酮对小鼠免疫功能的影响

［目的］研究红车轴草总黄酮对小鼠免疫功能的影响。［方法］设计迟发变态反应试验、炭粒廓清试验、脏器指数试验,每个试验均用40只小鼠,随机分成4组,设对照组与高、中、低剂量3个试验组。3个试验组分别给予85 mg/（kg·d）（高剂量组）,53 mg/（kg·d）（中剂量组）,22 mg/（kg·d）（低剂量组）红车轴草总黄酮灌胃,对照组以吐温-盐水液灌胃。［结果］3个试验组48 h足跖增厚与对照组均有增加,以中剂量试验组增加显著（P〈0.05）;中剂量组与低剂量组的吞噬指数较对照组有显著增高（P〈0.05）;脏器指数试验结果表明,试验组与对照组均有增加,但没有显著的统计学意义。［结论］试验全面评价了红车轴草总黄酮的各种生理药理功能及其对免疫功能的影响,为其开发应用提供了可靠的参考资料。     

不同盐胁迫对白三叶种子萌发及幼苗生长的影响

采用不同浓度的NaCl、Na₂CO₃、Na₂SO₄溶液以及NaCl和Na₂CO₃ 的混合液,NaCl、Na₂CO₃和Na₂SO₄的混合液对白三叶种子进行胁迫处理,每个处理3个重复,测定白三叶种子的发芽率、发芽势、发芽指数、活力指数以及幼苗根长和苗高等指标。结果表明,与对照相比,随着NaCl、Na₂CO₃以及NaCl和Na₂CO₃ 混合液浓度的增加,白三叶的发芽率、发芽势、发芽指数、活力指数及幼苗的根长和苗高均呈下降趋势。随着Na₂SO₄及NaCl、Na₂CO₃和Na₂SO₄混合液浓度的增加,白三叶种子的发芽率、发芽势、发芽指数、活力指数呈先上升后下降趋势,幼苗的根长和苗高呈下降趋势。白三叶种子对不同类型盐的耐受性各异,对NaCl、Na₂CO₃、Na₂SO₄的耐受浓度阈值分别为300 mmol/L,100 mmol/L,150 mmol/L。     

新疆野生白三叶表型性状变异研究

以新疆13份白三叶(Trifolium repens)为材料,通过观测其株高、叶形、叶色、花色、茎长、茎节间长和千粒重等特征,研究新疆野生白三叶表型性状差异。结果表明:白三叶的各个指标在群体间存在显著差异,具有丰富的遗传多样性。通过聚类分析可将13个群体分为3类,呼图壁M单独聚为1类;呼图壁J、呼图壁K、呼图壁L、乌市南山D和昌吉F聚为1类;其余7个聚为1类。本研究结果能够为开展野生白三叶的生物学特性和遗传育种研究提供基础数据。     

Shikimate accumulation in nine weedy species following glyphosate application

Glyphosate is commonly used in a variety of weed control scenarios and plants respond biochemically by continuing to attempt to push carbon through the shikimate pathway. The result is an accumulation of shikimate in sensitive plants in the days immediately after application. This research determined shikimate accumulation dynamics in nine problematic plant species from 0 to 6 days after treatment (DAT). Ambrosia artemisiifolia, Trifolium repens and Conyza canadensis showed rising concentrations through 6 DAT to >4000 mg L^?1. Chenopodium album, Xanthium strumarium and Urochloa platyphylla showed concentrations levelling off to a constant of about 2000 mg L^?1. Ambrosia trifida, Amaranthus palmeri and Polygonum pensylvanicum generally showed lower levels of shikimate accumulation and concentrations were decreasing after 3 DAT. No apparent relationships were evident between shikimate accumulation pattern and plant growth rate or speed of glyphosate activity. There also appeared to be no pattern in the shikimate accumulation trends that would allow for an informed decision as to which of these species would be most likely to develop glyphosate resistance. Shikimate concentrations were in agreement between field and glasshouse conditions for C. canadensis, but did not agree with those from A. palmeri.