Mesophyll Protoplast Culture and Plant Regeneration of Oriental Planetree (Platanus orientalis)

Large populations of mesophyll protoplasts were released from the leaves of 1.5–2 month old sterile seedlings, with a high protoplast yield (3.7× 10 6g-1FW) after protoplast purification. The purified protoplasts were cultured in a modified K8p liquid medium supplemented with 0.5 mg/L 2,4-D, 1 mg/L NAA and 0.5 mg/L BA. Higher density (1× 106/ml) in the initial culture of protoplasts is favourable to the division of cultured mesophyll protoplasts of this woody species among the densities tested. The protoplasts started to divide after 6 days of culture, and achieved 26.8% division frequency by 14 days. Sustained divisions resulted in mass production of cell colonies and small calli in 8 weeks. The calli further grew to 2–3mm on the gelrite-solidified K8 medium supplemented with 0.2 mg/L NAA aud 0.5 mg/L BA. Then, they were transferred onto the MSB proliferation medium with 0.1 mg/L NAA and 0.25 mg/L BA, where compact and cream-coloured calli were formed. Shoot formation was initiated on MSB differentiation medium coraming 0.5 mg/L IAA, 1 mg/L each of BA and ZT. It was observed that the frequency of shoot formation was about 28.7%. Whole plantlets were regenerated upon transferring 3 cm shoots to 1/2MS medium with 0.5mg/L IBA and 0.1mg/L BA, from which they were already transplanted into pots and grew well in the phytotron of Shanghai Institute of Plant Physiology.     

The photoprotective role of epidermal anthocyanins and surface pubescence in young leaves of grapevine (Vitis vinifera)

BACKGROUND AND AIMS: Depending on cultivar, surfaces of young leaves of Vitis vinifera may be glabrous-green ('Soultanina') or transiently have anthocyanins ('Siriki') or pubescence ('Athiri'). A test is made of the hypothesis that anthocyanins and pubescence act as light screens affording a photoprotective advantage to the corresponding leaves, and an assessment is made of the magnitude of their effect. METHODS: Measurements were made on young leaves of the three cultivars in spring under field conditions. Photosynthetic gas-exchange and in vivo chlorophyll fluorescence were measured. Photosynthetic and photoprotective pigments were analysed by HPLC. KEY RESULTS: Compared with glabrous-green leaves, both anthocyanic and pubescent leaves had greater dark-adapted PSII photochemical efficiency and net photosynthesis. In leaves possessing either anthocyanins or pubescence, the ratio of xanthophyll cycle components to total chlorophyll, and mid-day de-epoxidation state of the xanthophyll cycle were considerably smaller, than in glabrous-green leaves. These differences were more evident in pubescent leaves, probably indicating that trichomes were more effective in decreasing light stress than anthocyanins in the epidermis. CONCLUSIONS: Light screens, especially in the form of pubescence, decrease the risk of photoinhibition whilst allowing leaves to maintain a smaller content of xanthophyll cycle components and depend less on xanthophyll cycle energy dissipation. This combination of photoprotective features, i.e. decreased photon flux to the photosynthetic apparatus and lower xanthophyll cycle utilization rates may be particularly advantageous under stressful conditions.     

叶角、光呼吸和热耗散协同作用减轻大豆幼叶光抑制

研究了大豆叶片逐步展开过程中的色素组成、气体交换、荧光动力学以及叶片角度等特性。随着叶片展开程度的增加 ,叶绿素含量和叶绿素 a/ b比值增加 ;光合速率 (Pn)也增加 ,揭示叶片展开过程中光合机构是逐步完善的。自然状态下 ,不同展开程度的叶片均未发生明显的光抑制 ;但将叶片平展并暴露在 12 0 0μmol/ (m2 · s)光下时幼叶发生严重的光抑制 ,伴随叶面积的增加光抑制程度减轻。强光下 ,尽管幼叶光呼吸 (Pr)的测定值较低 ,但幼叶光呼吸与总光合之比 (Pr/ Pm)较高。将叶片平展置于强光下时 ,幼叶的实际光化学效率 (ΦPSII)明显下调 ,非光化学猝灭 (NPQ)大幅增加 ;幼叶叶黄素库较大 ,光下积累较多的脱环氧化组分 ,揭示幼叶依赖叶黄素循环的热耗散增强。自然条件下测量叶片角度 ,观察到在叶片展开过程中叶柄夹角逐渐增加 ;日动态过程中幼叶的悬挂角随光强增加而明显减小 ,完全展开叶的悬挂角变化幅度很小。叶片角度的变化使实际照射到幼叶叶表的光强减少。推测较强的光呼吸、依赖叶黄素循环的热耗散以及较大的叶角变化可能是自然状态下幼叶未发生严重光抑制的原因     

Sucrose and jasmonic acid interact in photosynthetic pigment metabolism and development of potato (Solanum tuberosum L. cv. Sante) grown in vitro

Potato (Solanum tuberosum L., cv. Sante) plantlets grown from stem node culture on medium supplemented with 90 mM sucrose accumulated lower amounts of photosynthetic pigments per mg dry weight in comparison to those grown on 30 mM sucrose. Addition of 0.1, 1 or 10 µM jasmonic acid (JA) to the medium resulted in a decrease of chlorophylls and carotenoids in the plantlets grown on either sucrose concentration. JA treatment induced de-epoxidation of violaxanthin to antheraxanthin and zeaxanthin only in those plantlets grown on a higher amount of sucrose in which hyperhydric symptoms were observed. The synergistic effect of JA and sucrose was clearly demonstrated in the plantlets grown on 90 mM sucrose and 1 µM JA. This was possibly due to overaccumulation of sucrose, the consequence of the most developed root system, and/or to stimulated water and solute transport by other mechanisms.     

Photosynthetic performance and water relations in young pubescent oak (Quercus pubescens) trees during drought stress and recovery

The capability to withstand and to recover from severe summer droughts is becoming an important issue for tree species in central Europe, as dry periods are predicted to occur more frequently over the coming decades. Changes in leaf gas exchange, chlorophyll a fluorescence and leaf compounds related to photoprotection were analysed in young Quercus pubescens trees under field conditions during two summers (2004 and 2005) of progressive drought and subsequent rewatering. Photochemistry was reversibly down-regulated and dissipation of excess energy was enhanced during the stress phase, while contents of leaf pigments and antioxidants were almost unaltered. Plant water status was restored immediately after rewatering. Net photosynthesis (P(n)) measured at ambient CO2 recovered from inhibition by drought within 4 wk. P(n) measured at elevated CO2--to overcome stomatal limitations--was restored after a few days. A network of photoprotective mechanisms acted in preserving the potential functionality of the photosynthetic apparatus during severe drought, leading to a rapid recovery of photosynthetic activity after rewatering. Thus, Q. pubescens seems to be capable of withstanding and surviving extreme drought events.     

Changes in the photosynthetic pigments in bean leaves during the first photoperiod of greening and the subsequent dark-phase. Comparison between old (10-d-old) leaves and young (2-d-old) leaves

Chlorophyll and carotenoid variations of 2-d-old and 10-d-old bean leaves (Phaseolus vulgaris var Red Kidney) were analyzed by HPLC during the first photoperiod of greening (16 h light + 8 h dark). The HPLC method used is suitable for the separation of cis- and trans-carotenoid isomers, Pchlide a and Chlide a as well as their esters. The main results are (1) before illumination the composition of the carotenoid pool is similar at the two developmental stages; (2) non-illuminated 2-d-old leaves are devoid of Pchlide a ester; (3) chlorophyll and carotenoid accumulation in 2-d-old leaves presented a lag phase twice longer than observed in 10-d-old ones; (4) Chlide a seems directly esterified to Chl a in 2-d-old leaves whereas esterification requires four steps in 10-d-old leaves and, (5) the kinetics of Chl and carotenoid accumulation are different at the two investigated developmental stages.     

北京地区油松、侧柏人工林叶面积指数变化规律

叶面积指数(LAI)是群体结构的重要参数,也是衡量林分质量的重要指标。通过光学测量方法和遥感技术等手段测量的大范围LAI需要进一步的地面实测验证。以北京十三陵林场为研究区,利用CI-110植冠分析仪和野外实测的69个油松和侧柏林分LAI为基础,分析了有效叶面积指数(LAIe)与实测叶面积指数(LAIa)的关系。结果表明,油松林的LAIe/LAIa之值在35.52%~36.36%;侧柏林的LAIe/LAIa之值在14.60%~16.72%。由于测定的油松、侧柏林分郁闭度在0.5~0.8,符合生态公益林的经营要求,因此油松、侧柏林的LAI是合适的,可以作为油松、侧柏林林分质量调控的一个重要依据。     

侧柏和北美香柏(柏科)的传粉机制(英)

观察了侧柏（Phaycladusorientalis（L．）Franco）和北美香柏（ThujaoccidentalisL．）散粉后花粉进入珠孔的过程。在散粉期,这两种植物的胚珠均分泌出传粉滴。当花粉落到传粉滴上后,引起传粉滴表面的形状发生改变或减弱胚珠的继续分泌,使得该传粉滴蒸腾加快,导致其比未授粉的传粉滴明显收缩。观察结果表明：不同植物的花粉导致侧柏传粉滴的收缩速率不尽相同。其中,与侧柏亲缘关系较近的植物花粉引起传粉滴的收缩速率和侧柏自身花粉引起的传粉滴收缩速率相似;反之,收缩速率变慢。侧柏传粉滴的收缩可能主要是由于花粉减弱胚珠分泌的结果。     

Iron deficiency-induced changes in the photosynthetic pigment composition of field-grown pear (Pyrus communis L) leaves

In this work we characterize the changes induced by iron deficiency in the pigment composition of pear (Pyrus communis L.) leaves grown under high light intensities in field conditions in Spain. Iron deficiency induced decreases in neoxanthin and β-carotene concomitantly with decreases in chlorophyll a, whereas lutein and carotenoids within the xanthophyll cycle were less affected. Iron deficiency caused major increases in the lutein/chlorophyll a and xanthophyll cycle pigments/chlorophyll a molar ratios. The chlorophyll a/chlorophyll b ratio increased in response to iron deficiency. The carotenoids within the xanthophyll cycle in iron-deficient and in iron-sufficient (control) leaves underwent epoxidations and de-epoxidations in response to ambient light conditions. In control leaves dark-adapted for several hours, most of the xanthophyll cycle pigment pool was in the epoxidated form vio-laxanthin, whereas iron-deficient leaves had significant amounts of zeaxanthin. Iron-deficient leaves also exhibited an increased non-photochemical quenching, supporting the possibility of a role for pigments within the xanthophyll cycle in photoprotection.     

氮调控对盐环境下甜菜功能叶光系统Ⅱ荧光特性的影响

采用盆栽试验方法,以NaCl为盐分模拟不同盐度环境,研究了施氮(N)对盐环境下生长的甜菜(Beta vulgaris)功能叶光系统Ⅱ (PSⅡ)荧光特性的影响及光合色素含量的变化.结果表明:在轻度、中度及重度盐环境下,施N均能增大PSⅡ最大光化学效率(Fv/Fm)、PSⅡ潜在活性(Fv/Fo)、PSⅡ实际光量子产量(Y(Ⅱ))、非调节性能量耗散的量子产量(Y(NO))、相对电子传递速率(ETR)及光化学猝灭系数(qp),且在适宜的施N范围内(0-1.2 g·kg-1)上述参数随施N量的增加而增大.各叶绿素荧光参数光响应的结果表明,随着光强的增加,各处理下调节性能量耗散的量子产量(KNPQ))、ETR及非光化学猝灭系数(NPQ)旱上升趋势,相反,Y(Ⅱ)、Y(NO)及qp则呈下降趋势,在有效的光强范围内(0-1 000 μmol·m-2·s-1)施N提高了甜菜功能叶PSⅡ反应中心的开放程度,并且在高光强下调节PSⅡ耗散掉过剩的光能以避免对其反应中心造成伤害.各盐度环境下施N也显著增加了甜菜功能叶叶绿素与类胡萝卜素含量,增大了叶绿素a/叶绿素b值,且叶绿素与类胡萝卜素含量随施N水平的增加而增加.说明盐环境下施N能够增强甜菜功能叶PSⅡ的活性,提高PSⅡ光能利用率,从而增强其对盐渍环境的适应性.     

Organogenetic capacity of leaves: The significance of marginal blastozones in angiosperms

A new term — the blastozone — is proposed to designate regions of the shoot competent for organogenesis. It is argued that the notion of marginal meristems is based on the cell theory and thus may not be appropriate to elucidate the process of organ formation. For instance, with respect to the occurrence of initials and of an elevated cell division rate marginal meristems have been shown to be doubtful structures. Furthermore, organogenetic competent regions form only parts of the meristems of the shoot. The study of blastozones from an organismic perspective reveals primary morphogenetic events such as initiation, incorporation, and fusion processes. Loss of morphogenetic competence is associated with histogenetic events, e.g., trichome outgrowth, and indicates the onset of processes leading to maturation. The marginal blastozone of the leaf is then used up although meristem features continue to be expressed. A series of SEM studies in several genera exemplifies the proposed viewpoint, demonstrating some of the morphogenetic potentialities of angiosperm leaf marginal blastozones.     

Polyphenol deposition in leaf hairs of Olea europaea (Oleaceae) and Quercus ilex (Fagaceae)

The subcellular localization (cytoplasm, vacuoles, cell walls) of polyphenol compounds during the development of the multicellular nonglandular leaf hairs of Olea europaea (scales) and Quercus ilex (stellates), was investigated. Hairs of all developmental stages were treated with specific inducers of polyphenol fluorescence, and the bright yellow-green fluorescence of individual hairs was monitored with epifluorescence microscopy. During the early ontogenetic stages, bright fluorescence was emitted from the cytoplasm of the cells composing the multicellular shield of the scales of O. europaea. Transmission electron micrographs of the same stages showed that these cells possessed poor vacuolation and thin cell walls. The nucleus of these cells may be protected against ultraviolet-B radiation damage. The progressive vacuolation that occurred during maturation was followed by a shifting of the bright green-yellow fluorescence from the perinuclear region and the cytoplasm to the cell walls. The same trends were observed during the development of the nonglandular stellate hairs of Quercus ilex, in which maturation was also accompanied by a considerable secondary thickening of the cell walls. Despite the differences in morphology, high concentrations of polyphenol compounds are initially located mainly in the cytoplasm of the developing nonglandular hairs, and their deposition on the cell walls takes place during the secondary cell wall thickening. These structural changes during the development of the leaf hairs make them a very effective barrier against abiotic (uv-B radiation) and probably biotic (pathogenic) stresses.     

The impact of <Emphasis Type="Italic">trans</Emphasis>-zeatin <Emphasis Type="Italic">O</Emphasis>-glucosyltransferase gene over-expression in tobacco on pigment content and gas exchange

The responses of tobacco plants over-expressing trans-zeatin O-glucosyltransferase gene under constitutive or senescence-inducible promoter (35S:ZOG1 and SAG12:ZOG1) and of wild type (WT) plants to water stress and subsequent rehydration were compared. In plants sufficiently supplied with water, both transgenics have higher net photosynthetic rate (P_N) in upper and middle leaves and higher stomatal conductance (g_s) in middle leaves than WT. Water use efficiency (WUE = P_N/E) was higher in both transgenics than in WT. During prolonged water stress, both P_N and E declined to a similar extent in both transgenics and WT plants. However, 7 d after rehydration P_N in SAG:ZOG (upper and middle leaves) and 35S:ZOG (upper leaves) was higher than that in WT plants. Increased content of endogenous CKs in 35S:ZOG plants did not prevent their response to ABA application and the results obtained did not support concept of CK antagonism of ABA-induced stomatal closure. The chlorophyll (Chl) a+b content was mostly higher in both transgenics than in WT. During water stress and subsequent rehydration it remained unchanged in upper leaves, decreased slightly in middle leaves only of WT, while rapidly in lower leaves. Total degradation of Chl, carotenoids and xanthophyll cycle pigments (XCP) was found under severe water stress in lower leaves. Carotenoid and XCP contents in middle and upper leaves mostly increased during development of water stress and decreased after rehydration. While β-carotene content was mostly higher in WT, neoxanthin content was higher in transgenics especially in 35S:ZOG under severe stress and after rehydration. The higher content of XCP and degree of their deepoxidation were usually found in upper and middle leaves than in lower leaves with exception of SAG:ZOG plants during mild water stress.     

Using the rapid A‐Ci response (RACiR) in the Li‐Cor 6400 to measure developmental gradients of photosynthetic capacity in poplar

The rapid A‐C_i response (RACiR) technique alleviates limitations of measuring photosynthetic capacity by reducing the time needed to determine the maximum carboxylation rate (V_cmax) and electron transport rate (J_max) in leaves. Photosynthetic capacity and its relationships with leaf development are important for understanding ecological and agricultural productivity; however, our current understanding is incomplete. Here, we show that RACiR can be used in previous generation gas exchange systems (i.e., the LI‐6400) and apply this method to rapidly investigate developmental gradients of photosynthetic capacity in poplar. We compared RACiR‐determined V_cmax and J_max as well as respiration and stomatal conductance (g_s) across four stages of leaf expansion in Populus deltoides and the poplar hybrid 717‐1B4 (Populus tremula × Populus alba). These physiological data were paired with leaf traits including nitrogen concentration, chlorophyll concentrations, and specific leaf area. Several traits displayed developmental trends that differed between the poplar species, demonstrating the utility of RACiR approaches to rapidly generate accurate measures of photosynthetic capacity. By using both new and old machines, we have shown how more investigators will be able to incorporate measurements of important photosynthetic traits in future studies and further our understanding of relationships between development and leaf‐level physiology.     

Diel growth patterns of young soybean (Glycine max) leaflets are synchronous throughout different positions on a plant

Leaf growth is controlled by various internal and external factors. Leaves of dicotyledonous plants show pronounced diel (24 h) growth patterns that are controlled by the circadian clock. To date, it is still uncertain whether diel leaf growth patterns remain constant throughout the development of a plant. In this study, we followed growth from the primary leaves to leaflets of the seventh trifoliate leaf of soybean (Glycine max) on the same plants with a recently developed imaging‐based method under controlled conditions and at a high temporal resolution. We found that all leaflets displayed a consistent diel growth pattern with maximum growth towards the end of the night. In some leaves, growth maxima occurred somewhat later – at dawn – as long as the leaves were still in a very early developmental stage. Yet, overall, diel growth patterns of leaves from different positions within the canopy were highly synchronous. Therefore, the diel growth pattern of any leaf at a given point in time is representative for the overall diel growth pattern of the plant leaf canopy and a deviation from the normal diel growth pattern can indicate that the plant is currently facing stress.     

Accumulation of 1-(malonylamino)cyclopropane-1-carboxylic acid in ethylene-synthesizing tobacco leaves

During the hypersensitive reaction of Samsun NN tobacco to tobacco mosaic virus (TMV) the inoculated leaves synthesize large quantities of ethylene. At the same time, 1-(malonylamino)cyclopropane-1-carboxylic acid (MACC), a conjugate of the ethylene precursor 1-aminocyclopropane-1-carboxylic acid (ACC) accumulates. Smaller amounts of MACC are formed concomitant with ethylene synthesis during the normal development of tobacco leaves. The conjugate appears neither to be hydrolysed to liberate ACC, nor to be transported to other plant parts. Its accumulation thus reflects the history of the operation of the pathway of ethylene synthesis in the leaf. In floating leaf discs exogenously applied ACC was converted only slowly to both ethylene and MACC. More ethylene and less MACC were produced in darkness than in light, suggesting that environmental conditions may influence the ratio at which ACC in converted to either ethylene or MACC.     

The distribution of nitrate reductase in tomato (Lycopersicon esculentum) leaves as affected by age

The distribution of nitrate reductase (NR, EC 1.6.6.1.) in the leaves of single-stem tomato plants ( Lycopersicon esculentum Mill., cv. Vandenbergs Moneydor) was studied using an in vitro test. The activity decreased from young to old leaves. However, a low value (NR minimum) occurred in some leaves below the apex, usually in the almost completely expanded leaves, provided that the plants received sufficient nitrate to induce optimum NR activity in all the leaves. When insufficient nitrate was available there was NR in the young leaves only. The observed NR minimum coincided with a low value for soluble carbohydrates and amino acids. Since there was no extra export of labelled carbon from the leaves with the NR minimum, it is suggested that in the almost completely expanded leaves carbohydrates produced by photosynthesis are mainly used for the production of polysaccharides for new cell walls. Consequently, less are left for the production of keto acids, which can act as acceptors for reduced nitrogen. Therefore, less amino acids are produced, and this may result in a lowered protein synthesis, including a lowered synthesis of nitrate reductase.     

Morphology and morphogenesis of ensiform leaves, syndesmy of shoots and an understanding of the thalloid plant body in species of Apinagia, Mourera and Marathrum (Podostemaceae)

The flattened, irregularly shaped and lobed or dissected leaves of Apinagia riedelii , A. latifolia , A. goejei , Mourera aspera and Marathrum utile (subfamily Podostemoideae) are ensiform in structure. After the typical bifacial inception, further growth of leaves proceeds in the midrib area, i.e. in the median plane of the leaf. The lower leaf zone is characterized by a sheath that orientates 'at the side of the blade', i.e. at the adaxial edge of the sword-like leaf. The ensiform blades are lobed, incised or pinnately dissected with the tips terminated in elongated threads or thin filaments. Leaves of Apinagia riedelii resemble pinnately dissected compound leaves. The dissected structure represents a secondary superimposition of the ensiform shape and a parallel development to compound leaves. It is interpreted as an adaptation to the rapid current, established in the floating shoots of these aquatic plants. The basal portions of main shoots and successive branches are fused due to a retarded separation. Fusion of this kind has been termed a syndesmy. The fused region of shoots is superseded by the fusion of the lower leaf zones of (distichously positioned) adjacent leaves, occurring at their margins. The fused leaf bases form a cavity for the terminal flower bud of each shoot and cover it in the form of a hood. The flower buds are hidden from external view. The meristematic growing zones are thus protected and enclosed within the syndesmic plant body which, in this way, attains the 'thalloid' appearance especially developed in Apinagia goejei and A. latifolia but also present in the other species. The results of this study enable an understanding of the particular appearance of these Podostemoideae as modifications of the typical structures according to the 'principle of variable proportions'.  © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society , 2005, 147 , 47–71.     

Compartmentation of soluble carbohydrates,of starch and of malate in motor organs (pulvini) and other parts of Phaseolus coccineus L. leaves

Quantitative histochemistry was used to investigate the tissue-specific compartmentation of soluble carbohydrates (sucrose, glucose, fructose), starch and malate in the laminar pulvinus, leaf blade and petiole of Phaselous coccineus L. at day and night positions of diurnal leaf movement. Total carbohydrate levels measured in a series of cross sections along individual pulvini of 24-d-old plants showed only small differences between the day and night positions of the respective leaf. In contrast, the level of malate changed during diurnal leaf movement, especially in the central part of a pulvinus. The levels of glucose and fructose in the pulvinus increased towards the transition zones between the pulvinus and lamina, and pulvinus and petiole, and this trend was even more pronounced for starch. By contrast, sucrose levels were highest in the pulvinus proper. The transverse compartmentation of metabolites was studied in distinct, approx. 0.5-mm-thick tissue slices from the central part of a pulvinus. These were dissected further into up to 14 distinct subsamples (bundle, bundle sheath, motor tissues, flanks). Irrespective of the position of the leaf (day or night), the central vascular core and the surrounding bundle sheath had high levels of sucrose (up to 500 mmol-(kg DW)^–1) and low levels of glucose and fructose (below 100 mmol-(kg DW)^–1), while in the cortex the situation was reversed. In the night position the level of sucrose decreased by approx. 30% in the bundle sheath and the central vascular core but not in the other sections. We thus suggest that because of the relatively small diurnal changes in their cortical pools, soluble sugars are not involved in the osmotic processes resulting in leaf movement. In contrast, pulvini from 14-d-old plants showed an interesting diurnal change in starch and malate pools in the outermost layer of the extensor. Here starch increased at night while the malate pool was lowered nearly stoichiometrically. Inverse pool sizes were found in the day position of the respective leaves. Although less significant, the opposite diurnal variation occurred in samples taken from the flexor region. We thus were able to locate areas of different carbohydrate activities in the laminar pulvinus of P. coccineus. The central vascular core, including the bundle sheath, is involved in temporary storage of photoassimilates, and the cortical regions are responsible for osmotically driven leaf movement. The results are discussed with respect to guard-cell physiology.Abbreviations CLP cut-leaf pulvini - ILP intact-leaf pulvini This work was supported by a grant from the Deutsche Forschungsgemeinschaft.