The influence of some environmental factors on cytological and biometric parameters and chlorophyll content of <Emphasis Type="Italic">Deschampsia antarctica</Emphasis> Desv. in the maritime Antarctic

Under the environmental conditions of the Point Thomas Oasis (King George Island, the South Shetland Islands), we studied the influence of month-long artificial treatment with fresh water, salt water, and guano solution on the biometric characteristics, chlorophyll content, as well as the nuclear area of leaf parenchymal cells and nuclear DNA content, in a maritime Antarctic aboriginal plant Deschampsia antarctica. The modeled factors induced an increase in the generative shoot height and the length of the largest leaf but did not influence the number of flowers. Treatment with guano caused an increase in the chlorophyll a and b contents, while fresh water treatment only led to some increase in chlorophyll a. Fluctuations of physiologically significant traits, such as the nuclear area and DNA content in the leaf parenchyma cells of D. antarctica, have been traced under the influence of the studied factors. Understanding of the hierarchy of influence of these factors as well as and sensitivity of plants of this species to external agents require further investigation.     

叶绿素含量测定的简化

本文介绍一种避免称重、研磨、冲洗和过滤等繁琐步骤,仅将确定面积的叶片细丝用少量80%丙酮浸泡提取后便可比色计算的简便的测定叶绿素含量的方法。此法省时间、省溶剂,不受叶片含水量变化的干扰,适合于大批量叶片样品的测定,而且便于与以单位叶面积表示的光合速率联系起来分析实验结果。同时,指出一些可能影响测定结果的因素。     

Effect of Benzyladenine on DNA, RNA, Protein, and Chlorophyll Contents in Intact Bean Leaves: Differential Responses to Benzyladenine According to Leaf Age

Benzyladenine (BA) was applied to intact bean (Phaseolus vulgaris) leaves at different stages of their growth. Changes in the amounts of cellular constituents resulting from the different treatments were followed and compared. RNA, protein, and chlorophyll contents, dry weight, fresh weight, and leaf area per single leaf continued increasing when leaves were treated with BA from an early stage, whereas in untreated leaves all these values levelled off or declined with advancing age. Besides these changes, BA treatment induced an increase in the DNA content. Changes in RNA content was more remarkable in response to application or deprival of BA treatment than the corresponding ones in protein and chlorophyll contents. The pattern of response to BA varied greatly according to the age at which the leaf received the treatment. As leaves aged, they lost the ability to increase their area and fresh weight in response to BA. However, continuous treatment with BA from an early stage kept the leaves young and able to respond.     

多效唑和缩节胺对现蕾前忍冬枝叶生长及花蕾性状和有效成分含量的影响

以忍冬品种‘九丰一号’(Lonicera japonica‘Jiufeng 1’)为实验材料,采用叶面喷施方法研究了不同质量浓度多效唑和缩节胺对现蕾前(抽枝生长初期)枝叶生长和叶片叶绿素含量以及花蕾性状和花蕾中绿原酸和总黄酮含量的影响。结果显示:分别喷施100、400、700和1 000 mg·L-1多效唑和50、100、150和200 mg·L-1缩节胺后,多数处理组的开花枝条数、着花节数和叶绿素含量较对照CK1(水)有不同程度提高,但叶面积差异不明显。随处理时间延长,各处理组枝条节间长度总体上呈逐渐增加的趋势,其中多数处理组枝条节间长度增长缓慢。各处理的花蕾长度、百蕾鲜质量和干质量总体上小于CK1,而花蕾折干率、总黄酮含量和绿原酸含量显著或不显著高于CK1。此外,在喷施多效唑和缩节胺的同时喷施质量体积分数1.0%尿素和质量体积分数0.1%硼砂,忍冬的叶面积、着花节数、花蕾长度、折干率、百蕾鲜质量和干质量总体上有所提高,而绿原酸含量降低,但各指标的差异总体较小。研究结果表明:喷施适量多效唑和缩节胺可调控忍冬枝条生长,并能提高花蕾中总黄酮和绿原酸含量。     

Increase in DNA Content of Primary Leaves of Phaseolus vulgaris upon Decapitation

Changes in DNA content of bean (Phaseolus vulgaris) primaryleaves after decapitation were investigated. When apical budswere removed at 11 d, DNA content per leaf increased by about20% at 15 d and then decreased in parallel with the controls.The RNA and chlorophyll contents, fresh weight, and leaf areaexpressed on a single leaf basis changed in the same manneras the DNA content in response to decapitation. But when bothapical and lateral buds were removed, all these values continuedincreasing during the test period. Thus, growing lateral budsand apical buds have the same effect on the DNA change in primaryleaves as that due to ageing of the leaves. Cell number perleaf was not increased by any treatment, indicating that theobserved increase in the DNA content of primary leaves is ascribableto an increase in DNA per cell. Next, the whole shoots above the nodes of primary leaves wereremoved at various ages. The response of primary leaves to decapitationvaried according to their age. With age, they lost the abilityto increase their fresh weight, area, and chlorophyll contentbut not their DNA and RNA contents in response to decapitation.Decapitation stimulated chloroplast replication only withinthe period in which chloroplasts were replicating in controlleaves, but it induced chloroplast enlargement at any age. Therefore,the increase in DNA content after decapitation may be partiallydue to an increase in the amount of chloroplast DNA. When stems were heat-girdled above the nodes of the primaryleaves, these leaves showed responses similar to but smallerthan those to decapitation. The senescence of primary leavesseems to be controlled by the distribution of substances whichare transported from the roots.     

Growth and photosynthesis of pea plants under different iron supply

Soil conditions, leading to iron deficiency or toxicity, are widespread in nature. Our objective was to study the effect of Fe supply, ranging from complete deficiency to excess, on growth and on some photosynthetic indices of pea plants. Both iron deficiency and toxicity decreased shoot and root growth. Complete deficiency resulted in a lower shoot/root ratio and a higher content of dry biomass per unit of fresh biomass in roots, while iron excess led to higher content of dry biomass per unit of fresh biomass in shoot. Complete deficiency was also characterized by low chlorophyll and carotenoid content, elevated ratios of chlorophyll a/chlorophyll b and carotenoids/chlorophylls, a drop of photosynthetic rate per leaf area, and an increase of photosynthetic rate per chlorophyll. The stomatal resistance substantially increased, while the transpiration rate decreased. Smaller changes in stomatal resistance and transpiration rate, but not in photosynthetic rate per leaf area, were found under partial iron deficiency and under excess of iron. In the first case, the chlorophyll content decreased, while in the second it increased. The maximum efficiency of photosystem II was unaffected by iron supply. Even when no genetic or experimental differences existed, changes in growth, pigment content and photosynthesis due to variation of Fe supply depended on the type and severity of the imposed stress, as well as on the studied parameter. A combination of indices described better the effect of iron supply, especially when small differences were characterized.     

5-Azacytidine decreases fragmentation of nuclear DNA and pigment formation in first leaf cells of barley seedlings

Realization of programmed cell death in senescence represents an activation/inactivation of the respective gene. Enzymatic methylation of nuclear DNA with the creation of 5methylcytosine is one of the mechanisms, which can regulate gene activity in animal and plant cells. 5Azacytidine (5azaC) acts as an inhibitor of DNA methylation, and induces expression of a range of some genes including genes responsible for senescence. Fragmentation of nuclear DNA is one of the hallmarks of programmed cell death in apoptosis pathway in plant cells. The influence of 5azaC (100 microg/ml) on nuclear DNS amount and its fragmentation in the first leaf cells of barley was studied. It was shown that in the first leaf cells of barley seedlings there is an apoptosis pathway of programmed cell death. It was also observed that nuclear DNA fragmentation under the 5azaC influence is strongly inhibited, and the DNA amount in the first leaf increases. Synthesis and destruction of chlorophyll also play a significant role in programmed cell death in plants. It was shown that under the 5azaC influence, the absorption spectrum of a pigment does not change in leaves and coleoptiles in the light, whereas in the dark condition, these pigments are not created under the 5azaC influence.     

Effects of Polyploidy on Photosynthetic Rates, Photosynthetic Enzymes, Contents of DNA, Chlorophyll, and Sizes and Numbers of Photosynthetic Cells in the C(4) Dicot Atriplex confertifolia

Photosynthetic rates, chlorophyll content, and activities of several photosynthetic enzymes were determined per cell, per unit DNA, and per unit leaf area in five ploidal levels of the C₄ dicot Atriplex confertifolia. Volumes of bundle sheath and mesophyll protoplasts were measured in enzymatic digestions of leaf tissue. Photosynthetic rates per cell, contents of DNA per cell, and activities of the bundle sheath enzymes ribulose 1,5-bisphosphate carboxylase (RuBPC) and NAD-malic enzyme per cell were correlated with ploidal level at 99% or 95% confidence levels, and the results suggested a near proportional relationship between gene dosage and gene products. There was also a high correlation between volume of mesophyll and bundle sheath cells and the ploidal level. Contents of DNA per cell, activity of RuBPC per cell, and volumes of cells were correlated with photosynthetic rate per cell at the 95% confidence level. The mesophyll cells did not respond to changes in ploidy like the bundle sheath cells. In the mesophyll cells the chlorophyll content per cell was constant at different ploidal levels, there was less increase in cell volume than in bundle sheath cells with an increase in ploidy, and there was not a significant correlation (at 95% level) of phosphoenolpyruvate carboxylase activity or content and pyruvate,Pi dikinase activity with increase in ploidy. The number of photosynthetic cells per unit leaf area progressively decreased with increasing ploidy from diploid to hexaploid, but thereafter remained constant in octaploid and decaploid plants. Numbers of cells per leaf area were not correlated with cell volumes. The mean photosynthetic rates per unit leaf area were lowest in the diploid, similar in 4×, 6×, and 8×, and highest in the decaploid. The photosynthetic rate per leaf area was highly correlated with the DNA content per leaf area.     

不同海拔对七子花叶片色素含量、含水量及比叶面积的影响

通过比较浙江大盘山不同海拔(A1:550~660 m,A2:700~800 m,A3:900~990 m,A4:1 000~1 015 m,A5:1 020~1 100 m)七子花(Heptacodium miconioides)叶片色素含量、含水量及比叶面积变化,探讨不同海拔对七子花生长的影响。结果表明,随着海拔的升高,叶绿素含量(包括叶绿素a、叶绿素b、叶绿素a+b)先增加后减少,在A3达最高值;叶绿素a/b比值、类胡萝卜素含量变化呈先低后高,在A3降至最低;比叶面积及叶片含水量,在较高海拔A4、A5都明显下降。七子花通过叶片色素、比叶面积、干重和含水量的变化以适应高海拔环境。     

供氮水平对小麦生殖生长时期叶片光合速率、NR活性和核酸含量及产量的影响

在水培条件下，研究了氮素水平对小麦生殖生长时期一些生理特性及产量的影响。结果表明：生殖生长时期，外源供氮水平供应增加，叶面积、叶片光合速率及叶绿素含量均随之增加；叶片和根系硝酸还原酶活性（NRA）、叶片铵态氮含量和外源供氮水平间有显著正相关；根系DNA及RNA含量均随供氮水平升高而升高；孕穗期用不同氮素水平处理15 d，对小麦成熟后生物量及经济产量有明显影响。     

Ontogenetic variations on absorption and utilization of phosphorus in common bean cultivars under biological nitrogen fixation

Salinity is a major yield-reducing factor in coastal and arid, irrigated rice production systems. Salt tolerance is a major breeding objective. Three rice cultivars with different levels of salt tolerance were studied in the field for growth, sodium uptake, leaf chlorophyll content, specific leaf area (SLA), sodium concentration and leaf CO₂ exchange rates (CER) at photosynthetic active radiation (PAR)-saturation. Plants were grown in Ndiaye, Senegal, at a research station of the West Africa Rice Development Association (WARDA), during the hot dry season (HDS) and the wet season (WS) 1994 under irrigation with fresh or saline water (flood water electrical conductivity = 3.5 mS cm^-1). Relative leaf chlorophyll content (SPAD method) and root, stem, leaf blade and panicle dry weight were measured at weekly intervals throughout both seasons. Specific leaf area was measured on eight dates, and CER and leaf sodium content were measured at mid-season on the first (topmost) and second leaf. Salinity reduced yields to nearly zero and dry-matter accumulation by 90% for the susceptible cultivar in the HDS, but increased leaf chlorophyll content and CER at PAR- saturation. The increase in CER, which was also observed in the other cultivars and seasons, was explained by a combination of two hypotheses: leaf chlorophyll content was limited by the available N resources in controls, but not in salt-stressed plants; and the sodium concentrations were not high enough to cause early leaf senescence and chlorophyll degradation. The growth reductions were attributed to loss of assimilates (mechanisms unknown) that must have occurred after export from the sites of assimilation. The apparent, recurrent losses of assimilates, which were between 8% and 49% according to simulation with the crop model for potential yields in irrigated rice, ORYZA S, might be partly due to root decomposition and exudation. Possibly more importantly, energy-consuming processes, such as osmoregulation, interception of sodium and potassium from the transpiration stream in leaf sheaths and their subsequent storage, drained the assimilate supply. This revised version was published online in August 2006 with corrections to the Cover Date.     

Leaf Senescence: Correlated with Increased Levels of Membrane Permeability and Lipid Peroxidation, and Decreased Levels of Superoxide Dismutase and Catalase

The changes in membrane permeability (soluble leakage), lipidperoxidation, and activities of superoxide dismutase (SOD) andcatalase have been studied during in situ senescence of leavesof Nicotiana tabacum L., cv. Wisconsin 38. After full leaf expansionwas reached there was a rapid, almost linear increase in therate of ⁸⁶Rb leakage from the preloaded leaf discs, with leafage. Parallel with this increase in membrane permeability wasa cumulative increase in the level of lipid peroxidation. Atthe same leaf age there were changes in the activities of SODand catalase. SOD activity decreased on the basis of fresh weightbut did not change when measured on the basis of protein contentprobably due to relative stability of SOD during the senescence-associatedgeneral decline in protein content. Catalase activity firstincreased parallel with the chlorophyll content of the leafand then, after full leaf expansion, declined on the basis ofboth fresh weight and protein content. These changes in membranepermeability, lipid peroxidation, and the enzyme activitiescoincide in leaf age with the decline in protein and chlorophyllcontents and in chlorophyll a: b ratio. When the senescenceof the bottom-most leaves was reversed by removing the stemfrom immediately above them, the senescence-associated changesin protein and chlorophyll contents, lipid peroxidation, andthe enzyme activities were also reversed. It is suggested thatleaf senescence may be a consequence of cumulative membranedeterioration due to increasing level of lipid peroxidationprobably controlled by, among other factors, the activitiesof SOD and catalase.     

PP333对离体苹果苗的生长及其生理的影响

在生根培养基中加入0.5或2.0PPm PP333, 明显地减少了苹果离体新梢的鲜重和干重、叶片鲜重和叶面积,增加了比叶重、根的鲜重和干重及根梢鲜重和干重比,并促进了根的形成。PP333对单位叶重量的叶绿素含量没有影响,而增加了单位叶面积的叶绿素含量。经PP333处理后,叶片中的淀粉含量、过氧化物酶活性、蛋白质和游离氨基酸的含量均明显高于对照,可溶性糖与对照差异不明显。     

Photosynthetic Characteristics of Photoautotrophically Cultured Cells of Tobacco

The photosynthetic characteristics of photoautotrophically culturedcells of tobacco (Nicotiana tabacum cv. Samsun NN) as well asthose of photomixotrophically cultured cells and green leaveswere investigated. Analyses revealed that on a fresh weightbasis cultured tobacco cells had lower chlorophyll contentsthan cells of green leaves. The chlorophyll content per chloro-plast,however, was almost the same in both types of cell, and thechloroplast number per cell accounted for only small differencesin the cellular chlorophyll content. This indicates that thelarger cell volume of cultured cells is the main factor in thedifference in the chlorophyll content of these cells. Photosynthetic activity measurements also showed differencesin the chloroplasts of cultured and leaf cells. The maximumactivities of photosystem I and the Hill reaction for the culturedcells were about half those for leaf cells on a per unit chlorophyllbasis. Moreover, photo-autotrophic cells had relatively constantphotosystem I and Hill reaction activities during growth; whereas,on a fresh weight basis these activities in leaf cells reflecteddevelopmental changes in the chlorophyll content. Lithium dodecyl sulfate-polyacrylamide gel electrophoresis showedqualitatively similar thylakoid polypeptide compositions forcultured and leaf cells at all stages of growth even thoughthere were quantitative decreases in the contents of severalpolypeptides in the cultured green cells (especially in photomixotrophiccells) in comparison to the polypeptide contents of tobaccoleaves. We speculate that the lower photosynthetic activityof the cultured cells may be caused by this reduction in thecontents of certain thylakoid polypeptides. (Received November 14, 1988; Accepted June 19, 1989)     

Nuclear DNA regulates the level of ribulose 1,5-bisphosphate carboxylase oxygenase in Medicago sativa L.

Summary The response to selection for leaf proteins was studied during three selection cycles. Selection for high total nitrogen content showed 75% heritability, and the levels of both ribulose 1,5-bisphosphate carboxylase oxygenase (Rubisco) and cytoplasmic protein were strongly under nuclear DNA control. High and low protein content were correlated with chloroplast area. Although the amounts of nuclear DNA were similar, the ratio of Rubisco/DNA and chlorophyll/DNA changed during the selection process. It can be concluded that the levels of Rubisco achieved in mature plants of M. sativa are under nuclear DNA control. The possible involvement of small subunit (SSU) genes in controlling these levels is discussed.     

Effect of certain dicarboxylic acid monoesters on growth,chlorophyll content,chlorophyllase and peroxidase activities,and gas-exchange of young maize plants

The effect of some dicarboxylic acid monoesters on growth, chlorophyll content, chlorophyllase (EC 3.1.1.14), and total peroxidase (EC 1.11.1.7.) activities was examined in detached and intact leaves of maize (Zea mays) plants grown in a greenhouse. The -monomethyl ester of itaconic acid (MEIA) at 1250 ppm had no effect on growth. However, application of the monoethyl ester of succinic (MESA) and monoethyl ester of adipic (MEAdA) acids (1250 ppm) resulted in an increased leaf area, fresh and dry weight of leaves and stems. These compounds retarded chlorophyll degradation in both detached and intact leaves. Chlorophyllase activity of the control and treated leaves was measured and related to chlorophyll content. Delaying of senescence by treatment with monoesters resulted in greater chlorophyll and protein content, compared with the control. However, the chlorophyllase activity/chlorophylla ratio in the treated plants decreased. Total peroxidase activity was higher in senescent leaves, but all treatments inhibited the increase of this enzyme activity. Prolonged carbon assimilative activity and enhanced leaf water use efficiency in treated plants was noted.     

Leaf cell water and enzyme activity

This work supports further the thesis that under conditions of water stress, cell water content may supersede hormonal regulation in effecting enzyme activity, thus becoming a regulatory factor in cellular metabolism. Addition of NaCl to the root medium of barley plants (Hordeum vulgare L.) markedly increased leaf RNase activity parallel to an increase of leaf water saturation deficit (WSD). Kinetin and abscisic acid, applied to the salinated plants, also modified RNase activity, as well as leaf-WSD. The familiar pattern of effects of these hormones on leaf RNase as well as leaf chlorophyll content was inverted, kinetin effected a relative increase in RNase activity and a decrease in leaf chlorophyll, whereas abscisic acid effected a relative decrease in RNase activity and maintained chlorophyll content. A close relationship between enzyme activity and leaf WSD became evident when leaf RNase and protease activities in the salinated plants were plotted against leaf WSD. This close relationship was maintained irrespective of the hormonal treatments, which in themselves markedly modified leaf WSD. As predicted, high relative humidity which relived the leaves from salt-induced water stress prevented the salt-induced rise in RNase activity.     

水分胁迫下烯效唑对百日草幼苗光合特性及叶解剖结构的影响

以百日草‘芳菲1号’为试材,研究不同水分胁迫下烯效唑(S3307)对其幼苗生长、光合特性及叶解剖结构的影响,以明确S3307对百日草的抗旱作用及其机理。结果显示:(1)在水分胁迫下,百日草的生长均受到不同程度的抑制,叶绿素含量显著降低,光合作用受到抑制,叶解剖结构有所变化。(2)S3307处理后,均能够显著降低所对应的不同程度水分胁迫下百日草的株高,显著增加茎粗、叶面积、叶片厚度、栅栏组织厚度和根冠比,显著增加叶绿素含量,提高百日草的净光合速率(Pn)、气孔导度(Gs)、蒸腾速率(Tr)和水分利用效率(WUE)。研究表明,S3307能够提高百日草的抗旱性,而且在轻度和中度水分胁迫下Pn的下降主要是由气孔因素引起,而在重度水分胁迫下光合速率的下降是由非气孔因素引起的。     

两种相思叶片光合作用对干旱的反应

比较了绢毛相思和大叶相思的叶特性,旱季的田间光合速率和供水短缺对光合速率、气孔传导率和蒸腾速率的影响。绢毛相思的比叶重、单位叶面积的叶绿素含量和叶绿素a/b均较大叶相思高,但叶片含水量略低。绢毛相思的中午时叶片水势为-0.6±0.05MPa,而大叶相思则为-1.18±0.07MPa。绢毛相思叶片水势降低时,叶片鲜重的变化较大叶相思大。旱季10月,两种相思的日平均光合速率相近似,但绢毛相思有较高的气孔传导率和蒸腾速率。干旱处理引起大叶相思叶片水势降低较绢毛相思大。当绢毛相思叶片水势从-0.76MPa降至-1.35MPa,日平均光合速率降低49.4％;而大叶相思,叶片水势从-1.22MPa降低至-2.2MPa,日平均光合速率降低55.0%。大叶相思叶片水势降低的幅度比较大,光合速率降低亦大。     

Leaf acclimation to experimental climate warming in meadow plants of different functional types

The use of open-top chambers (OTCs) installed in natural plant cover is one of the approaches to study plant responses to climate change. Three OTCs made from polyethylene film were installed on a herbgrass meadow in the subzone of the southern taiga before the beginning of the growing season. A significant increase in the average daily temperature values (by 0.5°C) and the relative humidity (by 10%) compared to control conditions was observed inside the chambers. Plant height, leaf parameters, and the pigments content were studied for six species of meadow plants during the growing season in two variants—inside the chamber and outside the chamber (control); more than 20 quantitative parameters of the mesophyll were studied for four of the species. It was found that the differences in microclimatic conditions had no effect on plant height and leaf area. A slight decrease in the thickness and density of the leaves and an increased water content were noted inside the OTCs. In contrast to weak changes in external leaf parameters, the internal leaf structure and the content of photosynthetic pigments varied considerably. Warming caused the reduction of the content of chlorophyll and carotenoids per unit leaf area in the majority of studied species, except for Veronica chamaedrys L., but the ratio of pigment forms did not change. Changes in the pigments content in the leaf were associated with some structural rearrangements in the mesophyll, whose mechanism depended on the functional properties of the species. Increased size of palisade cells and the number of chloroplasts per cell was noted in the ruderal species (R/CSR-strategist) Taraxacum officinale Wigg. s. l.; the reduction of chlorophyll content per leaf area occurred due to the decrease in chlorophyll content per a single chloroplast. Decreased number of cells and chloroplasts per leaf unit area without any changes in their size was marked for the species with S/CSR strategy Alchemilla vulgaris L. s. 1. and V. chamaedrys L. in a chamber, but the content of chlorophyll per a chloroplast increased. An increase in the number of cells and a simultaneous decrease in their size was observed in CR-strategist Cirsium setosum (Willd.) Bess. inside the OTC; the chlorophyll content per chloroplast did not change. It was concluded that the acclimation of plants to short-term climate warming was associated with the restructuring of leaf mesophyll, whose mechanism depended on the functional properties of the species.