油菜苗期叶片光合特性研究

通过测定油菜苗期叶片的光合强度,分析光强、温度、施肥等因素与光合强度的关系,结果表明：（1）油菜苗期不同叶位的我合强度、呼吸强度有较大差异,两者均以植株上最大叶最高;不同品种间光合强度也有明显的差异。（2）油菜叶片的光合强度与光照强度有密切关系,0-20klx范围内,光俣强度随着光照强度的增加而提高,其光饱和点约为20-30klx,光补偿点为2.8-4.5klx。（3）由菜叶片光合作用的最适温度为20-25℃,而呼吸作用在30℃时最旺盛。（4）施肥对油菜叶片的光合强度有一定影响,但远小于对叶面积的影响。     

旱碱地增施叶面肥对减氮棉田冠层光分布及产量的影响

为了研究机采种植模式下不同水平减施氮肥后增施叶面肥对棉花花铃期冠层光分布、叶面积指数及与产量的影响,旱碱地条件下,设置0（CK）、60（N1）、90（N2）、120（N3）、150（N4）、180（N5,当地常规施氮量）、225 kg·hm^－2 （N6）7个施氮水平,其中N1～N4喷施叶面肥4次,测定花铃期群体叶面积指数（Leaf area index, LAI）、冠层光分布和籽棉产量。结果表明：与当地常规施氮量相比,减施（60～150 kg·hm^－2）氮肥后,棉花花铃期叶面积指数降低0.7%～5.5%,冠层光总截获率降低0.2～1.7百分点,冠层光透射率升高0.2～0.8百分点;各减施氮肥处理群体叶面积指数与冠层上层叶片的光截获率均呈显著正相关,与下层叶片的光截获率则呈负相关;籽棉产量随施氮量的减少而降低,二者有较高的相关性（R²＝0.990 5）。减氮（90～150 kg·hm^－2）增施叶面肥处理的LAI、冠层光总截获率、光透射率、冠层上下层叶片光截获率以及籽棉产量与当地常规施氮量180 kg·hm^－2处理差异均不显著。综上,旱碱地机采模式棉田增施叶面肥,对减施氮肥棉花花铃期冠层光分布、叶面积指数及籽棉产量有一定补偿作用。     

旱碱地增施叶面肥对减氮棉田冠层光分布及产量的影响

为了研究机采种植模式下不同水平减施氮肥后增施叶面肥对棉花花铃期冠层光分布、叶面积指数及与产量的影响,旱碱地条件下,设置0（CK）、60（N1）、90（N2）、120（N3）、150（N4）、180（N5,当地常规施氮量）、225 kg·hm^－2 （N6）7个施氮水平,其中N1～N4喷施叶面肥4次,测定花铃期群体叶面积指数（Leaf area index, LAI）、冠层光分布和籽棉产量。结果表明：与当地常规施氮量相比,减施（60～150 kg·hm^－2）氮肥后,棉花花铃期叶面积指数降低0.7%～5.5%,冠层光总截获率降低0.2～1.7百分点,冠层光透射率升高0.2～0.8百分点;各减施氮肥处理群体叶面积指数与冠层上层叶片的光截获率均呈显著正相关,与下层叶片的光截获率则呈负相关;籽棉产量随施氮量的减少而降低,二者有较高的相关性（R²＝0.990 5）。减氮（90～150 kg·hm^－2）增施叶面肥处理的LAI、冠层光总截获率、光透射率、冠层上下层叶片光截获率以及籽棉产量与当地常规施氮量180 kg·hm^－2处理差异均不显著。综上,旱碱地机采模式棉田增施叶面肥,对减施氮肥棉花花铃期冠层光分布、叶面积指数及籽棉产量有一定补偿作用。     

穗肥运筹对超级杂交稻淦鑫688源库特征和氮肥效益的影响

通过不同穗肥运筹方式,探讨前氮后移对超级杂交稻组合淦鑫688源库特征的影响。结果表明,适量氮肥后移有利于优化群体质量、协调源库关系、增强叶片功能、延长叶片功能期、提高氮肥利用效益。抽穗后,叶面积指数和叶绿素含量随穗肥用量的增加而提高,而叶面积指数和叶绿素含量的下降速率随穗肥用量的增加而减缓。适量增施穗肥,可延长下位叶功能期,提高抽穗期茎鞘物质贮藏量、总库容量和单位叶面积承载的库容量,提高成穗率和结实率,减少籽粒库对茎鞘物质的需求量,提高植株抗倒伏能力,还能提高N素的物质生产力和稻谷生产力,提高N素吸施比和N素总积累量。对于淦鑫688而言,在施N量为175～205kg/hm2时,穗肥用量以占总施N量的40%～45%为好。     

施氮量对茶树生长及叶片光合特性的影响

采用水泥池培育的方法,研究了不同氮肥施用量对茶树生长和叶片光合特性的影响。试验设置4个施氮水平,分别为0kg N/hm2（CK）、112.5 kg N/hm2（N1）、225 kg N/hm2（N2）和450 kg N/hm2（N3）。结果表明：施氮显著促进茶树生长,施氮处理茶叶产量比CK显著提高116.98%～141.51%（P〈0.05）,但施氮处理间差异不显著（P〉0.05）;施氮处理茶树叶片叶绿素总量提高30.56%～72.67%,类胡萝卜素含量降低13.37%～29.74%,并与CK差异显著（P〈0.05）;施氮处理茶树叶片净光合速率比CK显著提高14.88%～17.26%（P〈0.05）,但施氮处理间差异不显著（P〉0.05）;氮肥施用提高茶树叶片气孔导度、蒸腾速率和水分利用效率。适量的施氮可提高茶树叶片叶绿素含量、提高光合速率,促进茶树生长和茶叶产量提高;但随着氮肥施用量的增加,单位氮肥对茶树生长的促进效应降低。     

利用SPAD值诊断赣花7号氮素营养研究

为适时精确诊断赣花7号的氮素营养状况,通过设置6个氮素水平（施纯氮0、75、150、225、300、375 kg/hm2）,在不同时期（出苗后30、45、60、75和90 d）分别测定花生不同叶位（主茎倒一完全叶、倒二完全叶和倒三完全叶）的SPAD值和相应叶位叶片的含氮量,分析其施氮水平、SPAD值和叶片含氮量之间的关系,并进行方程的拟合。结果显示：施氮水平与SPAD值、叶片含氮量之间呈显著的指数相关,SPAD值和叶片含氮量之间呈显著的线性相关,并且在各叶位中,以主茎倒3叶的相关性最好,其可作为氮素诊断的理想叶位。     

杂交稻氮素水平与物质生产关系的研究

对杂交稻“特优６３”Ｎ素水平与物质生产关系的研究结果明确：①随施Ｎ量增加，叶片含Ｎ率提高，叶面积扩大，净光合率在未到行前随之提高，到行后随之下降。因而营养器官贮藏物质的积累和中后期干物质积累速率以适量施Ｎ的处理（本试验为亩施Ｎ１１ｋｇ）为最高，产量也最高。施Ｎ过多，颖花大量退化，穗粒数、结实率，千粒重下降；施Ｎ过少，穗少穗短，单位面积总颖花数显著减少。②叶片含Ｎ率与产量呈二次曲线关系，相关达显著，极显著水平，苞分化，孕穗和齐德期最适叶片含Ｎ率分别为４．３３％，３．０３％和２．８３％。叶片含Ｎ率可望作为经济合理施Ｎ的量化指标之一。     

甘蔗苗期不同叶位叶绿素荧光特性研究

为明确不同叶位和叶片不同部位叶绿素荧光特性的分布规律及其随生长时间的变化规律,进而实现甘蔗光合潜力的快速评价,本研究通过桶栽试验对3个甘蔗主栽品种（ROC22、ROC16、桂柳05-136）不同叶位和叶片不同部位的叶绿素荧光特性进行比较分析,并研究叶绿素荧光参数对生长时间的响应。结果表明：光系统II（PSII）量子效率（ΦII）随着倒数叶位的增加而下降,在叶片不同部位之间表现为叶中部>叶尖端>叶基部,相同叶位不同品种间ΦII的差异不显著;可调节性能量耗散（ΦNPQ）则随着倒数叶位的增加而上升;非调节性能量耗散（ΦNO）在不同叶位（除倒四叶）及品种间并无显著差异。随着生长时间的推进,上部叶位具有较高的ΦII和较低的ΦNPQ;中部叶位的ΦII和光化学猝灭（qL）变化很小;下部叶位在叶片生长的前两周,能量分配在ΦII和ΦNPQ之间进行,ΦNO基本保持不变;而超过3周后,3个供试品种的ΦII、qL和最大光能利用效率（Fv/Fm）均有不同程度的下降,降幅为ΦII>qL>Fv/Fm,同时伴随着ΦNO的增加。上述结果表明光能利用效率以上部叶位最高,中部叶位稳定,而下部叶位最低且差异较为显著。而不同叶位相对电子传递速率（rETR）对生长时间的响应研究表明,在苗期上部第一片全展叶的中部叶位光能转化能力最强,可选择该叶片的中部叶位进行叶绿素荧光特性横向比较。本研究初步明确了不同叶位光能的利用效率及其随生长时间的变化趋势,为如何选择合适的叶位进行叶绿素荧光检测,进而开展甘蔗冠层光合潜力的快速评价奠定基础。     

不同穗型小麦品种叶重与叶面积关系的研究

本文以大穗型和多穗型小麦品种（系）为试材,研究了不同播种密度,不同生育时期,不同叶位叶片叶面积与叶干重,叶鲜重及单株干重的关系,结果表明：（１）叶干重,叶鲜重叶与叶面积的正相关都达到极显著水平,单株干重与叶面积的相关数显著在不同生育期表现不同;（２）叶干重与产量及其构成因素的相关关系和叶面积与产量及其构成因素的相关关系相似,且具有测定简便,受密度影响较小的特点,可以换算成叶面积或叶面积系数,建议作     

白肋烟不同叶位叶片的化学成分变化规律

在相同栽培条件下,对鄂烟1号不同叶位叶片的化学成分含量的变化规律进行研究,结果表明：（1）不同叶位叶片的无机非金属元素中,Cl和P随着叶位的变化,其含量变化波动较小,其中Cl的变化最小,且这两种元素的含量变化与叶位不存在相关性。（2）不同叶位叶片的无机金属元素中,Zn的变化程度最大,K、Mn、Ca以及Mg的含量变化均较小。在无机金属元素中,Zn与叶位呈显著相关性,K、Mn、Ca以及Mg与叶位均呈极显著相关。（3）不同叶位叶片的有机成分含量中,烟碱的含量变化最大,总N和总糖的含量变化程度小。烟碱与叶位呈极显著相关性,总N和总糖则与叶位不存在相关性。     

减氮对豫北限水灌溉冬小麦冠层结构和光合特性的影响

为了解节水栽培条件下冬小麦光合对减氮的反应,以豫北地区冬小麦为研究对象,在限水灌溉(春浇一水)条件下,以当地冬小麦生产中常规施氮量(底施氮量+追施氮量:120+210 kg·hm~(-2))为对照,设置不同减氮处理(底施氮量+追施氮量分别为120+150、120+90、120+0、0+0 kg·hm~(-2)),研究减氮对冬小麦冠层叶片和非叶器官形态特征、冠层光分布和光合速率的影响。结果表明,随施氮量的减少,小麦开花期单茎叶面积、上三叶面积及旗叶节以上非叶绿色器官面积均呈下降趋势,降幅分别为9.7%～28.0%、10.6%～30.3%和5.2%～16.8%,叶器官面积和上三叶面积下降幅度均高于旗叶节以上非叶绿色器官面积的下降幅度。减氮处理下,开花期上三叶长和宽分别减少4.4%～8.8%和11.8%～15.6%,叶片变窄变短,而倒四叶叶型无明显变化。另外,上三叶平均比叶重随氮肥减少总体呈增加趋势,表明适量减氮有助于改善上三叶叶片质量。随施氮量的减少,花后各叶层透光率呈增加趋势,其中灌浆中前期(开花至花后20 d)减氮处理的倒四叶层、倒三叶层、倒二叶层和旗叶层透光率分别比对照高39.0%、38.0%、23.8%和9.4%。随施氮量的减少,花后上三叶光合速率总体均呈先略升后降的趋势,其中旗叶和倒二叶光合速率在花后均以120+210 kg·hm~(-2)、120+150 kg·hm~(-2)和120+90 kg·hm~(-2)处理较高,且处理间差异较小,而倒三叶光合速率在开花至花后18 d均以120+150 kg·hm~(-2)和120+90 kg·hm~(-2)处理较高,分别比对照高38.7%和24.7%。这说明,减氮减少了冬小麦单茎叶面积,增加了非叶器官面积占单茎总光合面积的比例,且上三叶叶片变小,叶片质量提高,增加了花后冠层下部叶片受光比率,改善了冠层下部叶片的受光状况,有利于提高冠层下部叶片的光合速率。     

蔗叶过腹还田对甘蔗生长及土壤性状的影响

在N、P、K养分相等的情况下 ,探讨了蔗叶过腹(牛粪)还田、蔗叶过腹配施化肥 (N、P、K)、单施化肥 (N、P、K)3个处理对甘蔗生长和土壤性状的影响。结果表明 :蔗叶过腹还田可以提高甘蔗萌芽率和后期生长 ,但甘蔗糖份在3处理中最低 ;单施N、P、K化肥利于甘蔗的分蘖和前期生长 ,提高了成茎率 ;蔗叶过腹配施N、P、K化肥处理 ,甘蔗产量最高 ;分蘖初期、伸长期和成熟期的叶面积系数、 3叶叶绿素、 3叶比叶重在3种处理中差异不明显 ;3种处理均能提高土壤有机质含量和全氮含量 ,在一定程度上改善土壤通透状况 ,其中以蔗叶过腹还田处理效果最好     

Effect of nitrogen supply on leaf appearance,leaf growth,leaf nitrogen economy and photosynthetic capacity in maize (Zea mays L.)

Leaf area growth and nitrogen concentration per unit leaf area, N_a (g m⁻² N) are two options plants can use to adapt to nitrogen limitation. Previous work indicated that potato (Solanum tuberosum L.) adapts the size of leaves to maintain N_a and photosynthetic capacity per unit leaf area. This paper reports on the effect of N limitation on leaf area production and photosynthetic capacity in maize, a C4 cereal. Maize was grown in two experiments in pots in glasshouses with three (0.84–6.0 g N pot⁻¹) and five rates (0.5–6.0 g pot⁻¹) of N. Leaf tip and ligule appearance were monitored and final individual leaf area was determined. Changes with leaf age in leaf area, leaf N content and light-saturated photosynthetic capacity, P_max, were measured on two leaves per plant in each experiment. The final area of the largest leaf and total plant leaf area differed by 16 and 29% from the lowest to highest N supply, but leaf appearance rate and the duration of leaf expansion were unaffected. The N concentration of expanding leaves (N_a or %N in dry matter) differed by at least a factor 2 from the lowest to highest N supply. A hyperbolic function described the relation between P_max and N_a. The results confirm the ‘maize strategy’: leaf N content, photosynthetic capacity, and ultimately radiation use efficiency is more sensitive to nitrogen limitation than are leaf area expansion and light interception. The generality of the findings is discussed and it is suggested that at canopy level species showing the ‘potato strategy’ can be recognized from little effect of nitrogen supply on radiation use efficiency, while the reverse is true for species showing the ‘maize strategy’ for adaptation to N limitation.     

氮高效水稻主要源库性状的基本特点及其调控

【目的】本研究皆在阐明氮高效水稻源库性状的基本特点。【方法】在大田条件下,于2012-2014年设计了两个试验。2012年和2013年,以染色体单片段代换系遗传群体114个水稻株系为供试材料,依据成熟期吸氮量和产量两个性状将114个株系群体分为6种不同氮效率类型。2014年,在前2两年试验的基础上,以筛选出的氮高效株系(L68)和氮低效株系(L2)为供试材料,研究施氮量对两种氮效率水稻株系产量、源库性状的影响。【结果】1)114个株系群体成熟期吸氮量和产量差异均较大,吸氮量变幅为11.53~27.66 g/m~2,产量变幅为311.74~763.35 kg/666.7 m~2,随着吸氮量的增加,产量呈上升趋势。产量类型与吸氮量类型并不完全一致,高吸氮量是高产的重要基础,但产量还可能受到其他因素的影响;2)氮高效水稻抽穗期叶面积系数(包括有效叶面积、高效叶面积、总叶面积)、成熟期叶面积系数均显著大于氮低效水稻,叶面积构成因子中氮高效水稻绿叶质量明显高于氮低效水稻,但比叶重不同氮效率品种间差异较小;3)氮高效水稻单位面积库容量、单位面积颖花量显著高于氮低效水稻,氮高效水稻单位干质量、单位叶面积和单位氮素库容量大,库容形成能力强;4)氮高效水稻单位叶面积颖花数、单位叶面积籽粒产量大,结实期净同化率高,氮高效水稻"流"畅,叶片光合能力强;5)综合分析表明,库容量对氮素高效吸收影响较大。提高单位氮素库容量有助于提高单位面积库容量。不同施氮水平下,氮高效水稻叶面积系数、库容量、吸氮量和产量均明显高于氮低效水稻,叶面积系数在低氮水平下两者差异最大,其他3个指标以低、中氮差异较大。【结论】氮高效水稻源库指标均优于其他类型,且这一优势在不同施氮量亦是如此。     

耕作方式和施氮量对旱地冬小麦开花后干物质转运特征、糖含量及产量的影响

为探讨耕作方式和氮肥对旱地小麦的互作效应,在甘肃半干旱雨养农业区大田试验条件下,采用双因素裂区设计,以常规耕作(CT)、秸秆还田(CTI)、全膜覆土穴播(PM)、免耕秸秆覆盖(NTS)4种耕作方式为主区,75、150、225、300kg·hm~(-2)4个施氮量(分别用N1～N4表示)为副区,分析了不同耕作方式及施氮量组合处理下旱地冬小麦花后干物质转运、糖含量及产量的差异。结果表明,4种耕作方式中,PM的株高最高,叶面积最大,籽粒产量最高,较CT增产14.50%。PM增产主要是通过增加穗长和穗粒数来实现,也归因于花前营养器官干物质的积累量及其在花后向籽粒中转运量、转运效率和对籽粒产量的贡献率较CT显著增加,特别是增加了叶片和颖壳的干物质转运量、转运效率。CTI的千粒重和有效穗数虽然最高,但产量与CT无显著差异;NTS的株高、千粒重、有效穗数、干物质积累量和花后向籽粒中转运量均处于较低水平,产量较CT降低16.74%。施氮显著增加了旱地冬小麦的籽粒产量,平均产量表现为N4N2N3N1。CT、CTI、NTS下,施氮的增产作用显著,但PM下不显著。在所有处理中,PMN2的籽粒产量最高,比最低的NTSN1增加70.55%。施氮增产的原因主要是促进了不同器官干物质积累和开花后干物质转运。NTS提高了各器官的可溶性糖含量,但其效应在不同生育时期存在差异,茎秆主要表现在开花后20～30d,叶片和颖壳在开花后10～40d,叶鞘在开花后20～40d,籽粒在开花后10～30d。施氮显著降低了开花后0～30d茎秆和叶片的可溶性糖和蔗糖含量,但显著增加了开花后20d籽粒的可溶性糖含量。以上结果说明,在甘肃旱地雨养农业区,常规耕作、秸秆还田、全膜覆土穴播下冬小麦高产的氮肥施用量以中等水平(150kg·hm~(-2))最佳,免耕秸秆覆盖下需增加氮肥施用量(300kg·hm~(-2))。     

Responses of rice leaf thickness,SPAD readings and chlorophyll a/b ratios to different nitrogen supply rates in paddy field

The objective of this paper was to investigate the influence of different nitrogen (N) application rates to some morphological and physiological features of leaf blades, including leaf thickness, chlorophyll content at different leaf ages and chlorophyll a/b ratios. A paddy field and a cement tank experiments were conducted simultaneously. Rice leaf thickness was measured through a specially developed displacement sensor. Meanwhile, chlorophyll content was estimated using chlorophyll meter (SPAD) and spectrophotometer after ethanol extraction of leaf samples. With the increase of N application, leaf thickness became thinner and chlorophyll a/b ratios decreased. Moreover, the sensitivity of the SPAD readings of the same leaf at different leaf ages to N rates was assessed through coefficients of variation (CV). CV of SPAD readings increased from 8.8% to 21.6% during leaf lifetime, which indicates that SPAD readings became more and more sensitive to nitrogen rates as leaf aged. Therefore, SPAD readings of the lower leaves, which were physiologically older than the upper ones, were more sensitive to nitrogen rates.     

秧苗密度和施氮量对超高产杂交籼稻秧苗素质的影响

 2007年在云南省永胜县涛源乡水稻特殊高产生态区,利用杂交籼稻组合协优107,设计了氮肥处理（10.3、207、31.0和41.4 g/m2N）和秧苗密度处理（353、706、1059和1412苗/m2）双因子试验,旨在探讨施氮水平、秧苗密度和秧龄对超高产杂交籼稻秧苗素质的影响。结果表明：1)秧苗密度降低或施氮量增加,均降低出叶所需的有效积温,加快秧苗的出叶,且秧苗密度的效应更显著;2)高密度或低氮条件下,秧苗单株带蘖数随着秧龄的增加有减少的趋势;而在高氮或低密度条件下,秧苗单株带蘖数在播种后27 d（7叶期）内呈增加趋势,之后进入分蘖衰减期;3)施氮对秧苗新分蘖的发生和大分蘖保持、苗床叶面积指数的增大、单株干质量的增加以及植株含氮量的提高均有正效应;4)秧苗密度对秧苗新分蘖的发生和大分蘖保持、单株干质量的增加均有负效应,并比氮效应明显;对植株含氮量的提高也有一定的负效应;对苗床叶面积指数的增大有正效应。     

硫素水平对夏玉米产量及生理特性影响的研究

每公顷基施0(CK)、36.3(S1)、413.85(S2)kg硫时,玉米每公顷产量分别为9 784.5、10639.5和11322kg,处理分别比对照增产8.73%和15.71%,并提高了果穗长度,增加了穗行数和行粒数,对千粒重影响不大.玉米单株的千物质积累量、株高、绿叶面积、比叶重及光合势、净同化率均表现为S2>S1＞CK.施用硫肥后,提高了功能叶片的叶绿素a、b以及叶绿素总含量,但施硫处理间在前期差异不大,后期S2处理叶绿素含量较高,叶绿素a/b比值各处理间相对稳定.施用硫肥提高了玉米叶片的光合速率,表现为S2>S1＞CK.施用硫肥还提高了玉米植株的气孔导度和蒸腾速率.     

Land Equivalent Ratio of Groundnut-Fingermillet Intercrops as Affected by Plant Combination Ratio,and Nitrogen and Water Availability

Abstract

Field experiments were conducted to characterize intercropping advantages in groundnut-fingermillet intercrop in relation to crop combination ratios, soil moisture and nitrogen (N) availability. Three intercrops in 1 : 2, 1 : 1 and 2 : 1 alternating rows of groundnut and fingermillet were examined for their growth and yield in comparison with their respective sole crops in 1996. The effect of well watered (W) and water stressed (D) conditions on the intercropping advantage was also examined for 1 : 1 intercrops in 1995 and 1996. Fertilizer N was applied at the rate of 20 kg ha^?1 in 1995 and 50 kg ha^?1 in 1996. The total above-ground biomass (DM) and its land equivalent ratio (LER) were highest in the 1 : 1 combination ratio. The DM production of intercropped fingermillet was higher in 1996 with higher N than in 1995 with low N application, while those of groundnut were similar in both years. The intercropped groundnut exhibited significantly higher DM production after the fingermillet harvest. The LERs in grain yield were higher in 1996 (1.43 under W and 1.45 under D), than in 1995 (0.87 under W and 1.22 under D). Also, LERs were consistently higher under D than W conditions. Water stress severely reduced the leaf area index (LAI) of fingermillet at a low N, especially in the later stages, whereas higher N alleviated the water stress effect. A close linear relationship was observed between LAI and leaf area (LA) per unit leaf N both for groundnut and fingermillet, with intercrops producing larger LA per unit leaf N than sole crops. Intercropping maintained higher ability in leaf net photosynthesis and transpiration of groundnut up to later stages, and significantly reduced water evaporation from the soil surface under the canopy than sole cropping of fingermillet. These results suggest that three processes associated with the intercropping yield advantages in the groundnut-fingermillet intercrop; 1) higher leaf photosynthesis and vigorous growth of groundnut after the fingermillet harvest, 2) higher LA production per unit N and 3) efficient water use. In conclusion, interspecific shading was considered to be the key mechanism associated with these processes, leading to the intercropping advantages. The degree of the interspecific shade and its effect on growth and yield depended on the available soil N and water.     

The effects of variety, cutting interval and nitrogen application on the morphology and development of stolons and leaves of white clover

Six varieties of white clover, each grown with perennial ryegrass, four intervals between cuts and two levels of applied nitrogen in all combinations, were compared in a field experiment during the first 27 months after sowing. Information about yields, crop fractions, heights and ryegrass tillers has been presented in an earlier paper (Wilman and Asiegbu, 1982). The present paper is concerned with the more detailed studies of white clover, which help to explain the yield results and contribute to the understanding of the response of this species to management when grown in competition with grass. Increasing the interval between harvests increased the length of clover stolon per unit area of ground and increased stolon diameter, petiole length, weight per leaf and number of leaves harvested as a proportion of the number present in the sward while only slightly reducing the rate of leaf emergence, helping to explain the positive effect of increasing the interval on clover yield noted in the earlier paper. During regrowth, successive leaves had longer petioles and the length of individual petioles increased beyond the stage at which the leaflets were fully opened. Weight per leaf in clover increased considerably from April to June and declined to below the April value by October. It was shown that weight per leaf can be greatly increased by increasing the interval between harvests without reducing the number of leaves harvested per unit area per year. The stolon length measurements provided some support for the view that medium large-leaved varieties of white clover can with advantage be defoliated rather less frequently than small-leaved varieties. Stolon length was less adversely affected by applied N in the medium large- than in the small-leaved varieties. The small-leaved varieties had thinner stolons than the medium large-leaved varieties but about twice the stolon length when no N was applied, and a relatively high proportion of leaves which escaped defoliation. The application of N reduced stolon diameter, increased petiole length and had little or no effect on weight per clover leaf.