The Effect of Copper Supply on the Senescence and the Retranslocation of Nutrients of the Oldest Leaf of Wheat

The contents of Cu, N, P, K, Zn, Mn and Ca were followed duringthe life of the oldest leaf of wheat plants (Triticum aestivumL. cv. Gamenya) grown at deficient and sufficient supplies ofCu. At both levels of Cu, the Cu content of the oldest leafbehaved in a similar way to the contents of N and Zn, whichdeclined markedly during leaf senescence. By contrast to Cu the P and K contents declined markedly, priorto leaf senescence, whereas the Ca and Mn contents increasedthroughout the life of the leaf and did not decline during leafsenescence. Interactions among Cu supply, the supply of other nutrients(e.g. N), and leaf senescence account for the variable mobilityof Cu in wheat. Similar interactions between nutrient supplyand senescence may explain contradictory reports on the redistributionof other nutrients which are variably mobile in plants.     

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.     

Autumn Retranslocation of Heavy Metals from Leaves of Woody Plants in Forest Ecosystems

Biology Bulletin - This paper examines the autumn retranslocation of heavy metals (HMs), namely Cu, Zn, and Cd, from the photosynthetic organs of woody plants. This study was carried out in the...     

The Effects of Increased Illumination and Shading on the Low-Light-Induced Decline in Photosynthesis in Cotton Leaves

An experiment was carried out to study whether low-light-induced damage to the photosynthetic system in leaves of cotton (Gossypium hirsutum cv. Deltapine) which are below the compensation point in the canopy can be arrested and reversed by increased illumination. In addition it was intended to find out whether the photosynthetic system in leaves of shade plants show a greater resistance to low-light-induced damage than leaves of plants from more exposed habitats. The plants were grown at high density, and increased illumination to the shade leaves in the canopy was achieved by thinning the stand. Thinning was carried out at two stages and its effects on the decline in the photosynthetic capacity of the 4th leaf were followed. An early thinning was carried out shortly after the 4th leaf dropped below the compensation point and a late thinning 2 weeks later. Comparison was also made between the low-light-induced damage to the photosynthetic capacity of the 4th leaf in plants grown under two light regimes during the progressive increase in self-shading of the 4th leaf within the canopy. It was observed that both types of thinning arrested the low-light-induced damage to the photosynthetic system in shade leaves. The decline in photosynthetic capacity of the 4th leaf was stopped after both early and late thinning. The dry weight of the shoot system in the early and late thinned plants was not significantly different. It was double that of the control plants. The plants thinned early did not have higher shoot weight than the late thinned plants since there was a rapid shedding of flowers and fruits after early thinning. The 4th leaf in the early thinned plants showed a 30% increase in chlorophyll content and dry weight per unit leaf area. It is suggested that shedding of flowers and fruits, and increases in chlorophyll and dry weight per unit leaf area in the early thinned plants were caused by a change in the hormonal balance of the plants. The photosynthetic system in leaves of shade plants showed a greater resistance to damage by low light intensity than the photosynthetic system in leaves of plants grown at higher light intensities.     

接种叶锈菌的小麦叶片胞间洗脱液对叶肉细胞原生质体微丝骨架的影响

用异硫氰酸 鬼笔环肽 (FITC Ph)标记和共聚焦激光扫描显微镜 (CLSM )观察发现 ,以具有激发子活性的接种叶锈菌的小麦叶片的胞间洗脱液 (IWF)处理叶肉细胞原生质体一定时间后 ,抗病小麦品种洛夫林 10的原生质体内微丝骨架保持完整的网络状结构 ,而感病品种 5 389的大部分微丝骨架处于解聚状态。同时 ,抗病品种因IWF处理诱发的防卫反应———H2 O2 突发和HR反应的程度 (用原生质体活力下降的程度表示 )也大大高于感病品种。用细胞松弛素D(CD)预处理抗病品种原生质体可以明显抑制IWF处理诱发的H2 O2突发和HR反应 ,表明微丝骨架的状态可能与抗病性有密切的关系 ,完整的微丝骨架是H2 O2 突发和HR反应的一个重要条件。     

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.     

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.     

Effects of Low Temperature on Winter Wheat and Cabbage Leaves

Contents of soluble proteins, proline and chlorophyll in winter wheat (Triticum aestivum cv. Doğu-88) and cabbage leaves (Brassica oleracea convar. acephala) during acclimation to low temperature were investigated. When both of the plants species were cold acclimated, soluble proteins, proline and chlorophyll contents were higher than in the controls (non-acclimated). Also protein patterns differed between the plants at control and cold conditions. This revised version was published online in July 2006 with corrections to the Cover Date.     

遮荫对香果树叶片生理特性及叶肉细胞超微结构的影响

设置全光照（L₀）、透光率60%（L₁）、透光率25%（L₂）、透光率10%（L₃）4种光环境,通过遮荫试验研究不同光照条件对香果树幼苗生理特性及叶肉细胞超微结构的影响。结果表明：遮荫影响叶片含水量及叶片形态。随着遮荫强度的加大,叶片含水量（LWC）递增,单叶面积（SLA）增加,单叶干重（SLW_d）和比叶重（LAM）减小,比叶面积（LAM）增大。遮荫条件下幼苗光合作用效率呈现显著变化。全光和L₁处理的P_n和T_r日变化呈明显的双峰曲线,出现了明显的"午休",其余处理的变化相对缓和,双峰和"午休"现象不明显;G_s的日变化与P_n类似。P_n和T_r的日均大小排序为L₁ > L₀ > L₂ > L₃。轻度遮光有利于香果树光合作用效率的提高。遮荫条件下叶片叶绿素和类胡萝卜素含量均有一定程度增加,且随着遮荫强度的加大其含量递增,提高了叶片的捕光能力。遮荫条件下MDA变化较为缓和,SOD、POD活性呈现先升后降的变化,但遮荫下的MDA含量始终小于全光照,可溶性糖也呈现类似的变化。全光下叶绿体与细胞壁平行分布,呈梭形,类囊体排列均匀,淀粉粒和嗜锇颗粒较少;遮荫条件下细胞内叶绿体数量有所增加,在整个细胞中占有比例显著增大,淀粉粒含量增多,类囊体排列紧密,堆叠程度增高,提高了弱光下的光合效率。适度遮荫香果树幼苗能维持正常的生理活动,但有效辐射光强须为自然光强的60%以上。     

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。     

The Effect of Shading on the Photosynthetic Rate and Longevity of Grass Leaves

The rate at which the net photosynthesis of grass leaves grownin bright light (119 W m^–2) decreased as they aged wasincreased by severe shading (to 21 W m^–2 or less). However,less severe shading (light intensities of 36 W m^–2 ormore) had no effect. The decrease in photosynthesis was unaffectedby whether the whole plant was shaded or only the leaf whosephotosynthesis was measured. In both shaded and unshaded leaves, photosynthesis measuredin bright light fell faster as the leaf aged than did photosynthesisin dim light. Both mesophyll and stomatal diffusion resistancesrose as the leaf aged but the former rose faster. The chlorophyllcontent fell only towards the end of the life of the leaves.     

Responses of Penultimate and Flag Leaves of Wheat to Different Nitrogen Supply

Uniculm wheat (Triticum aestivum L.) was grown to maturity at four concentrations of nitrogen corresponding to 3 (N1), 6 (N2), 9 (N3) and 12 (N4) g m^–2. Penultimate and flag leaves were examined throughout the ontogeny. Sub-optimal concentrations of N resulted in sharp decline in both area and dry mass of the leaves. Decline in leaf area was due to fewer mesophyll cells. Net photosynthetic rate (P_N) increased up to full expansion, remained constant for about a week and then declined. P_N, nitrogen, ribulose-1,5-bis-phosphate carboxylase/oxygenase (RuBPCO) amount and activity, chlorophyll and soluble protein contents were similar at all the N concentrations. Both amount and activity of RuBPCO in the flag leaf were about two fold higher as compared to penultimate leaf, but P_N was similar. This indicates the presence of an excess amount of RuBPCO in the flag leaf.     

Copper Supply in Relation to Content and Redistribution of Copper Among Organs of the Wheat Plant

The relationship of copper supply to the content and movementof copper among organs of wheat plants was examined at sevenstages in their growth from seedlings to maturity on a copperdeficient sand. In the absence of copper (Cu₀), plants becameseverely copper deficient and produced no grain; developmentof tillers, leaves, stems, and inflorescences was delayed andgrowth of roots strongly depressed; leaf senescence was retardedand tiller growth was prolonged. Application of a marginal supplyof copper (Cu₁) overcame all symptoms and promoted growth andgrain production. Increasing copper supply eightfold (Cu₂) didnot change vegetative or grain production. Copper concentrations in stems, individual leaves, and wholetops were highest and responded most strongly to copper supplywhen they were young. As they aged, Cu₁ and Cu₂ leaves lostcopper rapidly; the first Cu₀ leaves retained their copper andremained healthy for more than 7 weeks even though younger leavesdeveloped severe copper deficiency. In all treatments, lossof copper from the oldest leaf paralleled senescence and theloss of nitrogen. It is suggested that copper does not move out of plant leavesuntil they lose organic nitrogen compounds. As a result, copperbehaves in non-senescent leaves as if it is not mobile in plantphloem. But under conditions favouring senescence, copper ishighly mobile: in the present experiment, 67 per cent of thecopper present in vegetative organs of the Cu₂ primary shootat flowering moved from them during grain development and thiscould account for all of the copper found in the grain at maturity. The retention of copper by leaves before senescence, its rapidloss during senescence, and the effect of copper deficiencyin delaying senescence resulted in the oldest leaf of severelydeficient Cu₀ plants in the present experiment having a highercopper concentration than that of copper adequate Cu₁ and Cu₂plants. This behaviour could account for the many reports ofanomalous C-shaped ‘Piper-Steenbjerg’ curves inthe relationship of yield to copper concentrations in planttops. The coupling of copper movement from leaves to nitrogenmovement can also account for the unusually high values reportedfor critical concentrations of copper in tops of plants givenhigh levels of nitrogen fertilizers. Old organs should not be included in samples for diagnosis ofcopper deficiency. Only young organs should be used. In thepresent experiment, the copper concentration of young leavesgave a good indication of the copper status of wheat: a valueof 1 µg g^–1 in young leaves indicated copper deficiency. copper, nitrogen, phloem transport, mineral transport, deficiency diagnosis, wheat, Triticum aestivum L.     

Carbon Partitioning in Mature Leaves of Pepper: Effects of Daylength

Grange, R. 1. 1985. Carbon partitioning in mature leaves ofpepper: effects of daylength.—J. exp. Bot. 36: 1749–1759. The partitioning of recently fixed carbon has been examinedin mature pepper leaves grown in 6, 10 or 14 h photoperiodsat different irradiances chosen to give similar radiation integralsand in a 6 h photoperiod at the lowest of these irradiances.The partitioning of carbon into export, starch, sugars and respirationwas followed over the photopenod and the subsequent night ina mature leaf. The maximum export rate during the day (approximately 18 µgC cm^–2 leaf h^–1) was not significantly differentamong the treatments. Net photosynthesis rate was directly relatedto irradiance; the proportion of net photosynthesis exportedduring the day was 33% in 6-h days and 57% in 14-h days. Leafstarch accumulation (as a proportion of net photosynthesis rate)increased slightly when plants were grown in 6-h days. The remobilization of starch and sugars at night allowed exportrates to remain similar over 24 h when plants were grown in10-h or 14-h photoperiods. Leaves grown in 6-h days showed nosignificant changes in export rate during the first few hoursof night but exhausted their starch reserves during the nightand export rates declined. Sucrose and hexose levels decreased at the onset of darkness,but did not fall below 40 µg cm^–2 in plants grownin 10-h or 14-h photoperiods; when this level was reached after3–4 h of darkness, starch breakdown began. In leaves grownin both 6-h treatments, sucrose levels fell below 40 µgcm^–2 when starch reserves were depleted during the nightand the export rate decreased concurrently. The results are discussed in relation to the control of exportand starch metabolism in the leaf. Key words: Pepper, partitioning, daylength     

顽拗植物澳洲坚果成熟叶片DNA提取方法比较

目的:针对澳洲坚果成熟叶片中富含多糖、多酚等杂质的特点,建立澳洲坚果成熟叶片中提取高质量 DNA 的方法.方法:采用改良CTAB法和改良SDS法提取澳洲坚果样品的总DNA,并对产物进行紫外、电泳及PCR扩增检测.结果:改良CrAB法的平均产率为13.6μg/g,略低于改良SDS法18.5μg/g,但改良CTAB法可有效去除多糖等杂质,获得的基因组DNA质量高.OD260/OD280均在1.7～1.9之间.进行ISSR扩增可获得清晰、多态性好的条带.结论:改良CrAB法较之改良SDS法更适合于从澳洲坚果成熟叶片中提取高质量DNA.     

Growth and Nutrient Retranslocation in Needles of Radiata Pine in Relation to Nitrogen Supply

The effects of N application on tree growth and the retranslocationof N, P, and K from young needles to new growth were examinedin young radiata pine (Pinus radiata D. Don) trees. Nitrogen fertilization increased the number and size of needles,rates of shoot production, stem volume growth and tree biomass.Foliar N and P contents (µg per needle) fluctuated ina cyclic fashion with prominent phases of accumulation, retranslocationand replenishment. The patterns of these fluctuations in controland N-fertilized trees were similar, although the fluxes ofN, P and K in and out of needles were increased by N fertilization.Greater translocation (g per tree) of N and K from needles ofN fertilized trees occurred because fertilization increasedthe needle weight and the proportion of N and K retranslocatedfrom individual needles. Nitrogen fertilization increased theretranslocation of P largely as a result of higher needle mass.Trees supplied with more than adequate amounts of P in the soilretranslocated up to 58 per cent of the initial pool of P fromyoung needles. The periods of high retranslocation coincidedwith periods of high concentrations of soil mineral N and withshoot production. Conversely, the periods of rapid replenishmentof N and P into the needles coincided with the time of slowshoot growth and low concentration of soil mineral N. The growthrate of trees, rather than the availability of nutrients inthe soil was the main factor controlling retranslocation. For radiata pine, retranslocation from needles is not a mechanismspecific for coping with low soil fertility. It seems to bea mechanism which enhances the nutrient supply to apical growingpoints, especially during periods of flushing. Pinus radiata, nitrogen supply, shoot growth, nutrient fluctuations and retranslocation, nutrient use and adaptation     

小麦成熟胚高频植株再生系统的建立

在研究小麦成熟种子不同预处理时间、不同种类和浓度生长调节物质、分化培养基中是否添加CuSO4、不同外植体类型和不同放置方式对小麦成熟胚愈伤组织诱导和分化的基础上,建立了一套高效、可靠、重复性好的小麦成熟胚高频植株再生系统.以小麦成熟种子完整胚作为外植体的诱导频率为100%;除掉胚的原胚芽部位生长出的芽苗后,转分化的分化频率达到42.50%.