The Effect of Shading During Vegetative and Reproductive Growth on the Photosynthetic Capacity of Leaves in a Grass Sward

The decline in photosynthetic capacity of successive newly expandedleaves, which occurs as a vegetative grass sward increases inleaf area, was prevented in a field sward of S24 perennial ryegrass(Lolium perenne L.) by protecting tillers from shading by theirneighbours. This adds support for the view that the declineis caused by the shading of leaves during their expansion. However, in a flowering sward where there is no such decline,the photosynthetic capacity of leaves was not reduced by shadingthem with a plastic mesh during expansion, although it was bypegging down tillers so that they developed at the bottom ofthe sward. Lolium perenne, perennial rye-grass, photosynthetic capacity, growth, shading     

The Effects of Shading and Cutting Treatments on the Photosynthetic Rate of Ryegrass Leaves

As the leaf area of miniature simulated swards of S24 perennialreygrass (Lolium perenne L.) grown in controlled environmentincreased, successive leaves which expanded on the main stemof a sample plant within the sward had progressively lower photosyntheticcapacities. When the plants surrounding the sample plant were cut, the photosyntheticcapacity of the next leaf to expand was increased, whether ornot other leaves on the sample plant had been removed. Whenall fully expanded leaves on the sample plant were removed butthe surrounding plants left uncut, the photosynthetic capacityof successive leaves on the sample plant continued to decreaseas in uncut swards. These results support the view that the changes in photosyntheticcapacity in grass swards are consequences of changes in thelight climate of the developing leaf rather than of changesin demand for assimilates or growth substance supply. The declinein photosynthetic capactiy was contributed to by both stomataland residual diffusion resistances.     

遮荫对甜瓜叶片光合特性的影响

以适宜不同栽培条件的3个甜瓜品种为材料,研究了遮荫对其光合色素含量、净光合速率及比叶重等叶片特性的影响。结果表明:与正常光照相比,遮光处理能诱使甜瓜叶片叶绿素和类胡萝卜素含量显著提高,叶绿素a/b显著降低。全光照条件下,3个甜瓜品种的净光合速率日变化曲线均呈双峰型,有明显的"光合午休"现象,而在遮荫条件下则呈单峰曲线变化,且光合峰值出现的时间比全光照下推迟;遮光条件下甜瓜叶片气孔导度日变化曲线与其净光合速率日变化类似。3个品种间比叶重在全光照条件下差异不显著,但遮荫显著降低了壮龄叶片的比叶重,且遮荫强度越重,比叶重越小;品种‘黄河蜜3号’壮龄叶的比叶重降幅(31.83%)显著大于‘银帝’(27.22%)和‘玉金香’(26.01%)。可见,遮荫降低了甜瓜叶片的净光合速率和功能叶片的比叶重,植株通过增加自身叶片光合色素含量以增强对环境的适应性,缓解遮荫对其的影响,品种‘银帝’表现出较强的耐弱光性。     

遮阳对白花前胡叶片光合特性的影响

为规范白花前胡(Peucedanum praerupterum)种植和提高产量,对不同光强下白花前胡的光合特性进行了研究.结果表明,与遮阳40％和60％相比,对照(CK)和遮阳20％的白花前胡叶片具有更高的最大电子传递速率[分别为247.129和266.866μmol/(m2·s)]和最大净光合速率[分别为25.621...     

遮荫对半夏叶片光合色素与保护酶活性的影响

对半夏进行不同程度遮荫处理,研究了其生长过程中叶组织的光合色素含量、叶绿素a/b值、保护酶体系(SOD、POD、CAT)活性和丙二醛(MDA)含量的变化及其生理特性.结果表明:不同处理的半夏在生长过程中,光合色素的含量呈先升后降的趋势;与全光照相比,遮荫处理的叶绿素含量较高,叶绿素a/b值较低,类胡萝卜素含量在生长发育中早期较低而后期较高;SOD、POD、CAT活性呈由低到高再降低的趋势,MDA含量持续升高;遮荫处理的SOD、POD活性和MDA含量均低于全光照处理,CAT活性则表现为先高于后低于全光照处理.适度的遮荫可以提高半夏叶绿素的含量,降低膜系统受到的伤害,改善半夏的倒苗状况,为半夏叶片的生长提供较好的环境.     

Effect of Flowering on the Photosynthetic Capacity of Ryegrass Leaves Grown With and Without Natural Shading

The photosynthetic capacity of newly expanded leaves of vernalizedor non-vernalized plants of S24 perennial ryegrass (Lolium perenneL.), grown in long or short photoperiods, was measured in twoexperiments. In the first, leaves were protected from shadingduring development, while in the second, the natural shade ofneighbouring tillers in a sward was allowed. In the first experiment there was little effect of vernalization,day length or flowering, and leaves in all treatments had photosyntheticrates at 250 W m^–2 of between 28 and 32 mg CO₂ dm^–2h_–1.In the second experiment the photosynthetic rate of successiveleaves fell as sward leaf area increased. This downward trendwas reversed, however, in flowering tillers in the vernalizedlong-day treatment, while in the other treatments, which didnot flower, photosynthetic capacity continued to fall. It isconcluded that the leaves of reproductive tillers have highphotosynthetic capacities because stem extension carries themto the top of the canopy where they are well illuminated duringexpansion. Lolium perenneL, ryegrass, photosynthetic capacity, flowering, shading, vernalization     

遮荫对闽楠幼苗光合及其叶片解剖特性的影响

以2年生闽楠幼苗为材料,探讨不同遮荫处理［0(CK,全光照) 和30%、50%、70%遮荫］对闽楠［Phoebe bournei (Hemsl.) Yang］幼苗光合作用及其叶片解剖结构的影响,为闽楠的合理栽培及人工林混交树种的配置提供理论依据。结果表明：(1)与全光照处理(CK)相比,闽楠幼苗叶片净光合速率(P_n)、蒸腾速率(T_r)、气孔导度(G_s)、最大净光合速率(P_nmax) 、光饱和点(LSP)、光补偿点(LCP)及暗呼吸速率(Rd)均随遮荫强度的增加而显著下降;在30%和50%遮荫下,幼苗能通过提高水分利用效率(WUE)和表观量子效率(AQY),增加叶绿素含量来充分利用弱光环境;70%遮荫处理则影响闽楠幼苗的正常生长。(2)遮荫降低了闽楠幼苗叶片的气孔密度,但单个气孔器的面积显著增加;遮荫处理下,闽楠叶片和主脉明显变薄;栅栏组织和海绵组织厚度降低,排列稀疏,栅海比减小,有利于提高对光能的利用效率。(3)闽楠幼苗根、茎、叶及总生物量均在全光照下最大,遮荫抑制了植株生物量的积累。研究发现,闽楠幼苗在遮荫处理下生物量积累和光合效率降低,但同时在叶片解剖结构和功能上表现出对遮荫的适应性,从而表现出一定的耐荫性。     

遮荫对雪茄外包皮烟生长和光合特性的影响

采用全光照(Lck)与遮荫处理———透光率为71%(L1)、63%(L2)和22%(L3),对雪茄外包皮烟生长发育及其光合特性进行了研究.结果显示:(1)随着透光率的降低,烟株茎变细,叶片变薄;株高和叶面积各处理均先增加后降低,且在L2遮荫条件下株高和叶面积显著高于其它处理,分别达最大值(32.5 cm,47 620 cm2);根系干重显著降低,总干重先增加至透光率为63%时达最大值,当透光率降至22%时又显著降低;净光合效率(Pn)呈先增加后降低趋势,且在透光率为71%的遮荫条件下达最大值;(2)遮荫处理可显著提高雪茄外包皮烟叶绿素含量和Fv/F0值,使ΦpsⅡ、Fv/Fm和QP值增大、QN和Chl a/b的值降低.研究表明,透光率为63%的遮荫处理下雪茄外包皮烟植株地上部分生长最好.     

遮荫对黑茶藨子叶片形态结构和光合特性的影响

以黑茶藨子为试验材料,通过人工遮荫的方式,研究了不同遮荫强度（全光照、20%和60%遮荫）和遮荫时间（初期、中期和后期）对黑茶藨子叶片形态解剖结构和光合特性的影响。结果表明：（1）20%、60%遮荫处理的叶片厚度均显著低于全光照处理,上下表皮厚度则高于全光照处理;随着遮荫强度的加大,栅栏组织与海绵组织厚度比值大小均呈减少趋势,随着遮荫时间的延长,呈增加趋势。（2）遮荫初期和中期,20%遮荫处理的叶片净光合速率（P_n）比全光照和60%遮荫处理的值略高,但差异并不显著（P>0.05）,其蒸腾速率（T_r）、水分利用效率（WUE）也略有增加;但是,60%遮荫处理的叶片净光合速率（P_n）显著低于全光照处理（P<0.05）。遮荫后期,60%遮荫处理的叶片净光合速率（P_n）显著高于全光照处理,且水分利用效率（WUE）、气孔导度（G_s）、蒸腾速率（T_r）均显著高于全光照和20%遮荫处理。综上所述,遮荫处理导致叶片厚度减少,海绵组织比例增加,有利于减少透射光中的光量子丧失,提高光能利用效率;生长早期和中期作20%轻度遮荫处理,后期作60%中度遮荫处理能提高植株对光和水分的利用效率、维持较高的光合速率、延缓衰老。     

遮阴对谷子和花生光合特性的影响

本文论述了遮阴处理后不同光照强度对谷子(Setaria italica)和花生(Arachis hypogaea)某些光合特性的影响。这主要表现在它们的光补偿点和光饱和点都有所降低,在弱光下,净光合速率和光—光合曲线的最初斜率增大,尤其是相对光合速率的增高更为显著。同时,叶片的叶绿素含量增加,含水量增多,叶片厚度变薄,光合生产量下降。这些特点的变化趋势是一致的,只是变化的程度有所差别。另一方面,它们的光饱和光合速率对遮阴的反应却显然不同,谷子减低,花生几乎没有变化。由此可以看出,谷子属于阳性植物,而花生则近于耐阴植物。花生的耐阴性高于谷子。本文的某些数据可以为配置谷子或花生与高杆作物,如玉米或高粱,组成的间作群落结构提供参考。     

遮荫对虎耳草光合生理特性的影响

以盆栽1年的虎耳草为材料,研究遮荫条件下虎耳草叶片抗氧化酶体系活力、叶绿素含量、光合速率以及叶绿素荧光参数的变化,为虎耳草规模化栽培提供理论基础。结果表明：透光率50%条件下,叶绿素含量较高;虎耳草抗氧化酶活力最高;光饱和点（LSP）最大,最大光合速率（A_max）最高,光合速率日变化平均值最高,无“午休”;光系统Ⅱ的实际量子产量(Φ_PSⅡ)、PSⅡ最大量子产量(F_v/F_m)和光化学猝灭系数(qP)最高,非光化学猝灭系数(qN)最低。这表明,虎耳草在怀化地区的最适光照条件是50%左右的透光率。     

遮荫对紫叶李幼苗叶片色素含量及光合速率的影响

以露地栽培的1年生紫叶李和绿叶李为试材,研究了全光照(CK)、中度遮荫(透光率为43%)、重度遮荫(透光率为27%)处理下叶片色素含量及净光合速率的变化.结果表明:在夏季,各处理紫叶李幼苗叶片叶绿素含量、类胡萝卜素含量随遮荫时间的延长逐渐升高,花色素苷含量、花色素苷含量/叶绿素含量比值降低;在秋季,各处理紫叶李幼苗叶片叶绿素含量、类胡萝卜素含量先升高后降低,而花色素苷含量、花色素苷含量/叶绿素含量比值则先降低后升高.在夏秋两季,紫叶李3种色素含量均高于绿叶李,全光照下的紫叶李叶片花色素苷含量、花色素苷含量/叶绿素含量比值及净光合速率日积分值均高于遮荫处理.紫叶李具备一定的喜光性,全光照环境有利于其彩色的呈现和光合性能的发挥.     

钾营养对扬花期小麦旗叶光合速率日变化的影响

在田间栽培条件下,小麦旗叶的气孔导度、净光合速率与钾之间呈显著的正相关.钾可减少由于光合“午睡“造成的26.5%～37%的光合产量损失.     

遮阴对猫爪草光合特性及叶片解剖结构的影响

【目的】探究不同遮阴度对野生植物猫爪草（Ranunculus ternatus Thunb）光合特性和叶片解剖结构的影响,为深入了解其耐阴性以及开展规模化栽植提供理论基础。【方法】采用控制变量法,以盆栽猫爪草为试验材料,设置全光照（CK）、30%遮阴（T1）、50%遮阴（T2）、70%遮阴（T3）和90%遮阴（T4）5个处理,对不同遮阴处理下的光合特性及叶片解剖结构进行分析。【结果】（1）随着遮阴程度增加,叶面积在T3环境下达到最大值,株高和茎粗逐渐降低。（2）随遮阴程度的增加,叶片表观量子效率（AQE）先升后降,在T4处理下显著低于其他处理,而光饱和点（LSP）、光补偿点（LCP）、暗呼吸速率（Rd）和最大净光合速率（Pnmax）逐渐降低;最大荧光（Fm）、可变荧光（Fv）、最大化学效率（Fv/Fm）和PSⅡ潜在活性（Fv/F0）先升后降,初始荧光（F0）热耗散的电子比率（φDo）则先降后升。（3）随着遮阴程度的增加,叶片气孔密度先减后增,并在T3处理达到最小值,上下表皮厚度和海绵组织厚度逐渐降低,组织结构紧密度（CTR）先降后升,组织结构疏松度（SR）先升后降。（4）叶片栅栏组织、海绵组织、叶片厚度及上、下表皮厚度与Rd呈极显著或显著正相关关系;海绵组织厚度、CTR和SR与Pnmax ,以及栅海比（P/S）、SR与AQE均呈显著正相关关系;海绵组织厚度和SR与F0呈显著负相关关系。【结论】猫爪草可以通过降低光合速率和改变叶片结构来提高耐阴性,在全光照下生长良好,也能较好地适应30%-70%遮阴环境。     

The Growth Rate of Wheat Leaves in Relation to the Extension Zone Sugar Concentration Manipulated by Shading

The main objective of this study was to determine the relationshipbetween the relative rate of growth of emerging wheat leavesand the hexose sugar concentration of the extension zone. Shortperiods of intense shading (to 20 or 5% of full sun for up to14 d) were used to decrease hexose concentrations. Shading decreased hexose concentrations to a fraction of thatof controls and also resulted in thin and narrow leaves thatwere less in dry weight than control leaves of the same length.Shading did however increase the length of the zone of extendingtissue at the leaf base by 30%. The effect of hexose concentrations on the relative rate ofleaf growth was evaluated by determining the ratio between growthrates of shaded and control leaves. This ratio declined as hexoseconcentrations declined and the relationship was described bya rectangular hyperbola (r > 0.95, P < 0.01). Combineddata from many leaves on the main shoot and its tillers fromtwo irrigated wheat crops all conformed to the same relationship.The hexose concentrations where the ratio of growth rates washalf the maximum rate were 0.42 mg g^–1 fr. wt. for extensiongrowth and 1.74 mg g^–1 fr. wt. for dry weight growth.These values were significantly (P < 0.01) different. These results were compared with data from emerging leaves offield crops and it was concluded that hexose concentrationshad not limited leaf growth rates, the lowest values recordedbeing 2.5–3.0 mg g^–1 fr. wt. It was further suggestedas unlikely that leaf growth rates of wheat crops in the fieldwould be limited by hexose concentrations.     

谷子叶片光合速率日变化及水分利用效率

通过降低空气湿度（ 从约３０ ％ 减少到５ ％ ） 、增加ＣＯ２ 浓度（ 从４００ μｌ ＣＯ２／Ｌ增加到７３０ μｌ ＣＯ２／Ｌ） 、烫叶鞘破坏韧皮部等处理对谷子叶片光合速率日变化和水分利用效率（ＷＵＥ） 进行了研究, 发现中午光合速率降低与光合产物积累有关; 虽然低大气相对湿度（５ ％ ） 使光合速率有所降低,但提高了ＷＵＥ。而烫叶鞘使光合物质积累既抑制了光合速率,又降低了ＷＵＥ。     

苹果叶片的净光合速率和光能利用效率的动态模拟

根据构建的苹果叶片净光合速率（Pn）、气孔导度（Gs）和光能利用效率（LUE）的耦合模型可模拟一般小气候条件下苹果叶片的Pn和LUE变化。结果表明,小气候因子对Pn和LUE的影响不同,并且不同小气候因子之间还有明显交互作用。Pn主要由有效光合辐射（PAR）和CO2浓度决定,并随着叶片水势和空气湿度的升高而增大,正常条件下Pn的最适温度约为25℃,PAR、CO2浓度和空气湿度下降时,Pn的最适温度也随之下降。PAR值较小时,LUE与PAR正相关;在PAR达到400μmol·m-2·s-1左右时,LUE值最大,而后随着PAR的增加而减少。由于LUE是Pn和PAR的比值,所以其它小气候因子和叶片水势对LUE的影响与对Pn的影响相一致。     

The Effect of Manganese on the Assimilation and Respiration Rate of Isolated Rooted Leaves

The effect of manganese on carbon assimilation, respiration,and translocation has been studied using isolated rooted potatoleaves and small potato plants. Methods are described for therooting and culture of the leaves and plants. It was found thatnormal potato leaves rooted readily when treated with -naphtha-leneaceticacid (2 p.p.m.), but that very few of the manganese-deficientleaves produced roots, the critical level being about 15 p.p.m.manganese on a dry weight basis. The growth of isolated deficientleaves was also much less than that of control leaves, but inno case did characteristic manganese-deficiency symptoms develop,although the manganese level had fallen below that of leaveswhich showed symptoms when attached to the plant. A marked differencein net assimilation rate was found between leaves which hada high or low manganese content at the time of rooting. Theaddition of manganese after rooting to low manganese leavesdid not, however, cause an increase in assimilation rate, althoughthe manganese content of the leaves had been raised to thatof the control leaves. Manganese was shown to have only a smalleffect on respiration, higher respiration rate being consistentlyassociated with a higher manganese content; the addition ofmanganese to ‘deficient’ leaves did not cause anyincrease in respiration. No effect of manganese on translocationwas detected.