Growth and Water Relations of Lotus Creticus Creticus Plants as Affected by Salinity

Young plants of Lotus creticus creticus growing in a hydroponic culture were submitted to 0, 70 and 140 mM NaCl treatments for 28 d and the growth and ecophysiological characteristics of these plants have been studied. The growth of Lotus plants was not affected by salinity when applied for a short period (about 15 d); however, 140 mM NaCl induced a decrease in shoot RGR at the end of the treatment. The root growth was not decreased, even it was stimulated by 140 mM NaCl. The osmotic adjustment of Lotus plants at 70 and 140 mM NaCl maintained constant pressure potential, avoiding the visual wilting. For a similar leaf water potential, cuticular transpiration of salinized plants was lower than in control plants due to the salinity effect on the cuticle. Moreover, the presence of hairy leaves (60 and 160 trichomes per mm² in young and adult leaves, respectively) allows keeping almost 81 % of sprayed water and absorbing the 9 % of the water retained, decreased the epidermal conductance to water vapour diffusion.     

Water Relations Only Partly Explain the Distributions of Three Perennial Plant Species in a Semi-arid Environment

The water relations and stomatal conductances of three perennial plant species, Stipa tenacissima L., Anthyllis cytisoides L., and Retama sphaerocarpa (L.) Boiss., dominant on the upper slopes, mid-slopes and floor of a valley, respectively, in semi-arid south-east Spain, were investigated to test the hypothesis that differences in plant-soil water relations could account for the different distributions of each species in the catena. Diurnal measurements of water potential (Ψ_w), relative water content (RWC) and stomatal conductance (g_s) of leaves were made over one year. Leaf temperature, air humidity, wind-speed and incident quantum flux density were measured concurrently. Soil water content was determined gravimetrically at 0 – 5 cm and 15 – 20 cm depths. Measurements of Ψ_w, RWC and g_s were analysed according to meteorological conditions, based on the maxima for daily air temperature and atmospheric saturation water vapour deficit and on soil moisture content. The hypothesis that plant-soil water relations can explain the distribution of the three species along the catena from valley side to valley floor was rejected for Anthyllis and Stipa but confirmed for Retama. This revised version was published online in July 2006 with corrections to the Cover Date.     

Interspecific Differences of Leaf Gas Exchange and Water Relations of Three Evergreen Mediterranean Shrub Species

Leaf gas exchange and plant water relations of three co-occurring evergreen Mediterranean shrubs species, Quercus ilex L. and Phillyrea latifolia L. (typical evergreen sclerophyllous shrubs) and Cistus incanus L. (a drought semi-deciduous shrub), were investigated in order to evaluate possible differences in their adaptive strategies, in particular with respect to drought stress. C. incanus showed the highest annual rate of net photosynthetic rate (P _N) and stomatal conductance (g _s) decreasing by 67 and 69 %, respectively, in summer. P. latifolia and Q. ilex showed lower annual maximum P _N and g _s, although P _N was less lowered in summer (40 and 37 %, respectively). P. latifolia reached the lowest midday leaf water potential (₁) during the drought period (–3.54±0.36 MPa), 11 % lower than in C. incanus and 19 % lower than in Q. ilex. Leaf relative water content (RWC) showed the same trend as ₁. C. incanus showed the lowest RWC values during the drought period (60 %) while they were never below 76 % in P. latifolia and Q. ilex; moreover C. incanus showed the lowest recovery of ₁ at sunset. Hence the studied species are well adapted to the prevailing environment in Mediterranean climate areas, but they show different adaptive strategies that may be useful for their co-occurrence in the same habitat. However, Q. ilex and P. latifolia by their water use strategy seem to be less sensitive to drought stress than C. incanus.     

Somatic hybridization between birdsfoot trefoil (Lotus corniculatus L.) and L. conimbricensis Willd

Summary Somatic hybrid plants were produced by fusion of birdsfoot trefoil (Lotus corniculatus) cv Leo and L. conimbricensis Willd. protoplasts. Birdsfoot trefoil etiolated hypocotyl protoplasts were inactivated with iodoacetate to inhibit cell division prior to fusion with L. conimbricensis suspension culture protoplasts. L. conimbricensis protoplasts divided to form callus which did not regenerate plants. Thus, plant regeneration from protoplast-derived callus was used to tentatively identify somatic hybrid cell lines. Plants regenerated from three cell lines exhibited additive combinations of parental isozymes of phosphoglucomutase, and L. conimbricensis-specific esterases indicating that they were somatic hybrids. The somatic chromosome number of one somatic hybrid was 36. The other somatic hybrid exhibited variable chromosome numbers ranging from 33 to 40. These observations approximate the expected combination of the birdsfoot trefoil (2n=4x=24) and L. conimbricensis (2n=2x=12) genomes. Somatic hybrid flowers were less yellow than birdsfoot trefoil flowers and had purple keel tips, a trait inherited from the white flowered L. conimbricensis. Somatic hybrids also had inflorescence structure that was intermediate to the parents. Fifteen somatic hybrid plants regenerated from the three callus lines were male sterile. Successul fertilization in backcrosses with birdsfoot trefoil pollen has not yet been obtained suggesting that the hybrids are also female sterile. This is the first example of somatic hybridization between these two sexually incompatible Lotus species.Formerly USDA-ARS, St. Paul, Minn, USA     

Gas Exchange and Chlorophyll Fluorescence in Symbiotic and Non-Symbiotic Ryegrass Under Water Stress

The symbiotic association of endophyte fungus, Neotyphodium lolii, and ryegrass improves the ryegrass resistance to drought. This is shown by a 30 % increase in the number of suckers in infected plants (E+), compared to plants lacking endophyte (E−), and by a higher water potential in the E+ than E− plants. The E+ plants have higher stomatal conductance (g _s), transpiration rate, net photosynthetic rate (P _N), and photorespiratory electron transport rate than the E− plants. The maximal photochemical efficiency (F_v/F_m) and the actual photochemical efficiency (Φ_PS2) are not affected by the endophyte fungus. The increase in P _N of the E+ plants subjected to water stress was independent from internal CO₂ concentration. An increased P _N was observed in E+ plants also in optimal water supply. Hence the drought resistance of E+ plants results in increased g _s, P _N, and photorespiratory electron transport rate. This revised version was published online in June 2006 with corrections to the Cover Date.     

盐胁迫对鸡爪槭幼苗生长及其叶绿素荧光参数的影响

以鸡爪槭幼苗为材料,采用盆栽方法,研究了不同盐浓度[0.042%(对照)、0.2%、0.4%和0.6%]对鸡爪槭幼苗生长的伤害和叶绿素荧光参数的影响。结果显示:当土壤NaCl含量为0.2%、0.4%和0.6%时,鸡爪槭幼苗分别表现为轻度、中度和重度盐害;叶片含水量、叶绿素a和b及叶绿素总含量均随盐浓度的增加而显著下降,花色素苷含量则表现为随盐浓度的增大而显著上升,分别比对照高出48.7%、280.3%和382.7%;叶片叶绿素荧光参数PSⅡ潜在活性(Fv/Fo)、潜在量子效率(Fv/Fm)、光化学量子产量(Yield)、光合电子传递速率(ETR)、实际光化学效率(ΦPSⅡ)和光化学猝灭系数(qP)均随着盐浓度的增大呈显著下降趋势,但非光化学猝灭系数(NPQ)在低盐胁迫时则较对照显著提高,0.2%NaCl处理时比对照显著增加33.3%,而高盐胁迫下则显著下降。研究表明,盐胁迫显著抑制了鸡爪槭幼苗叶片叶绿素合成和光合作用进行,而幼苗叶片在低盐胁迫下则可能通过增加PSⅡ反应中心非辐射热能量耗散来保护光合机构不受损害,从而表现出一定的耐盐胁迫能力。     

限氮培养对小球藻水分含量和叶绿素荧光参数的影响

限氮培养是提高小球藻油脂含量的一种方法,本研究探讨了小球藻限氮培养过程中藻细胞的生物量、水分含量和叶绿素荧光参数的变化。结果表明:在限氮培养条件下,小球藻藻细胞的生物量和水分含量分别下降了18%和7%;藻细胞的最大光能转化效率(Fv/Fm),表观量子效率(α)和最大光合电子传递速率(rETRmax)在整个限氮培养过程中均快速下降,到培养末期下降至接近于0,显著低于对照;半饱和光强(Ek)在对数期迅速下降,到稳定期后显著上升;最小荧光(F0)在整个限氮培养过程中显著上升。可见,限氮培养显著影响了小球藻细胞光系统Ⅱ的结构和功能。     

Influence of Water Stress on Water Relations, Photosynthetic Parameters and Nitrogen Metabolism of Moth Bean Genotypes

Effects of water stress at pre-flowering stage were studied in three genotypes (RMO-40, Maru moth and CZM-32 E) of moth bean [Vigna aconitifolia (Jacq.) Marechal]. Increasing water stress progressively decreased plant water potential, leaf area, net photosynthetic rate, starch and soluble protein contents and nitrate reductase activity while contents of reducing sugars, total soluble sugar, free amino acids and free proline progressively increased. Significant genotypic differences were observed and genotype CZM-32-E displayed a better drought tolerance than other genotypes.     

Influence of Phosphorus Application on Water Relations, Biochemical Parameters and Gum Content in Cluster Bean Under Water Deficit

Relative water content (RWC), leaf water potential (_w) and osmotic potential (_s), contents of chlorophyll (Chl) a, Chl b, soluble sugars, and seed quality (gum content) were used to evaluate the role of phosphorus in alleviation of the deleterious effect of water deficit in clusterbean (Cyamopsis tetragonoloba L. Taub). Under water stress, _w, _s, and Chl and gum contents decreased and soluble sugar contents increased. Phosphorus application increased Chl and sugar contents in control plants and ameliorated negative effects of water stress.     

Chemical defense production in Lotus corniculatus L. II. Trade-offs among growth,reproduction and defense

Summary Ecological trade-offs between growth, reproduction and both condensed tannins and cyanogenic glycosides were examined in Lotus corniculatus by correlating shoot (leaves and stem) size and reproductive output with chemical concentrations. We found that cyanide concentration was not related to shoot size, but that condensed tannin concentrations were positively correlated with shoot size; larger plants contained higher tannin concentrations. Both tannin and cyanide concentrations were depressed when plants produced fruits. Defense costs change as plants mature and begin to reproduce. These trade-offs indicate that cost of defense chemical production cannot be predicted merely on the basis of molecular size, composition or concentration.     

8种木本植物木质部栓塞变化与生理生态指标关系的研究 I.与植物木质部水势的关系

以自然状况下生长良好的耐旱树种刺槐（Robinia pseudoacacia L.）、元宝枫（Acer truncatum Bge）、沙棘（Hippophae rhamnoides L.）、白榆（Ulmus pumila L.）、油松（Pinus tabulaeformis Carr.）、白皮松（Pinus bungeana Zucc.ex Endl.）及中生树种女贞（Ligustrum lucidum Ait.）、柳树（Salix matsudana Koidz.f.pendula Schneid.）为研究对象,用压力室法测定木质部水势,用冲洗法测定木质部栓塞程度,研究不同生长季节木质部栓塞与水势间的火系。结果表明：针叶树油松、白皮松在各个季节水势均较高,水势变化幅度较小,木质部不易发生栓塞,这与其木质部由管胞构成,对木质部栓塞不敏感,在干旱时采用高水势延迟脱水的耐旱策略有关。阔叶树刺槐、元宝枫、沙棘、白榆、女贞和柳树的木质部栓塞现象是其在每天正常生长过程中不可避免的“平常事件”,是它们适应干旱的一种方式。它们的木质部栓塞程度与水势表现出了相反的变化趋势,即同一树种在同一季节内水势值越低,木质部栓塞程度越大,但在不同树种及同一树种的不同季节不存在这种关系。由此可见,植物木质部栓塞对水势的敏感程度（即木质部栓塞脆弱性）主要由树种的木质部结构决定,同时受到树种特性、树木生长发育时期、外界环境因子的影响,木质部栓塞的脆弱性也具有季节变化特征。     

Water Stress Induced Changes in Anatomy of Tomato Leaf Epidermes

Anatomical changes of leaf epidermes of tomato plants (Lycopersicon esculentum Mill. cv. INCA 9) submitted to water stress in the preflowering stage were studied. 20 d after germination, plants were subjected to three treatments: 1) 100 % of evapotranspired water was applied every day, 2) from 100 up to 10 % of evapotranspired water was applied every day, and 3) water supply was completely suppressed. Trichome density was similar in apical, middle and basal zones, and adaxial and abaxial leaf surfaces. Stomatal density and length, and epidermal cell length and width had similar values on the same leaf surface, but the values were higher on the abaxial than on the adaxial leaf surface. The water deficit had little effect on number of trichomes, length and width of epidermal cells and length of stomata, and decreased the stomatal density especially on adaxial surface.     

Chemical defense production in Lotus corniculatus L. I. The effects of nitrogen source on growth,reproduction and defense

Summary The carbon to nitrogen balance theory was examined for a legume, Lotus corniculatus L., which allocates carbon to nitrogen fixation. N-fixation can influence the ratio of carbon to nitrogen in legumes by providing nitrogen in nutrient-poor habitats, and by consuming carbon for support of symbiotic N-fixation. L. corniculatus clones (genotypes) were grown under two levels of nitrogen fertilization: a treatment which suppressed nodulation with fertilization and a treatment which received no additional fertilization. These plants relied solely on symbiotic N-fixation. Plants which supported symbionts had lower biomass and lower tannin concentrations than fertilized plants; this appears to be a result of the large carbon demand on N-fixation. Plants supporting symbionts often had relatively lower protein concentrations than fertilized plants. Cyanide concentration was influenced by plant genotype but not by nitrogen source. Although symbiotic N-fixing plants were smaller, they had three times the reproductive output of fertilized plants.     

Evidence for the existence of 2n gametes in Lotus tenuis Wald. et Kit. (2n=2x=12): their relevance in evolution and breeding of Lotus corniculatus L. (2n=4x=24)

Summary Crosses between male sterile L. corniculatus (2n=4x=24) and L. tenuis (2n=2x=12) plants were performed in order to verify the presence of 2n gametes in L. tenuis. All but one of the plants from these crosses had 2n=4x=24 and the L. corniculatus phenotype; this plant had 2n=2x=12 and the L. tenuis phenotype. The plants also showed good quantity of pollen at tripping, good pollen fertility and good percentage of seed setting in the backcross to L. corniculatus. On the whole, both cytological and morphological observations, showing that all but one of the plants from L. corniculatus x L. tenuis were normal tetraploids, suggest the existence of diploandrous gametes in L. tenuis. On the other hand, haploid parthenogenesis probably gave origin to the dihaploid plant 2n=2x=12.     

Variation in a single protoplast- and seed-derived population of Lotus corniculatus L.

Summary Lotus comiculatus L. is a widely cultivated, outbreeding, leguminous forage crop. Seventy-one plants, most of which were tetraploid, were regenerated from calli derived from a single protoplast. Their morphological and agronomic traits were evaluated and compared with those of the seed-produced population. The variances of most of the traits in the protoplast-derived (protoclonal) population were smaller than those of the seed-produced population. Mean values of all the traits of the protoclonal population shifted significantly towards lower values. However, new phenotypic variants with higher values than those of the plant initially used for protoplast isolation were also observed. Plants with less hydrocyanic acid (which has a toxic effect on cattle) than the initial plant were obtained in the protoclones. Generally, the pollen fertility of protoclones was significantly low compared with the seed-produced plants. This seems to be partly due to the occurrence of abnormalities in chromosome structure during protoplast and/or callus culture, as suggested by the formation of univalents, lagging, and fragment chromosomes and bridges at metaphase I and anaphase I and II of the regenerants. The changes in chromosome structure, however, did not induce any malformed morphologies.     

Artichoke Leaf Morphology and Surface Features in Different Micropropagation Stages

Artichoke (Cynara scolymus L.) leaf size and shape, glandular and covering trichomes, stomatal density, stomata shape, pore area and epicuticular waxes during micropropagation stages were studied by scanning electron microscopy (SEM) and morphometric analysis with the aim to improve the survival rate after transfer to greenhouse conditions. Leaves from in vitro shoots at the proliferation stage showed a spatular shape, ring-shaped stomata, a large number of glandular trichomes and juvenile covering hairs, but failed to show any epicuticular waxes. Leaves from in vitro plants at the root elongation stage showed a lanceolated elliptic shape with a serrated border, elliptical stomata, decreased pore area percentage, stomatal density, and mature covering trichomes. One week after transfer to ex vitro conditions, epicuticular waxes appeared on the leaf surface and stomata and pore area were smaller as compared to in vitro plants. Artichoke acclimatization may be improved by hormonal stimulation of root development, since useful morphological changes on leaves occurred during root elongation.     

Leaf Gas Exchange and Water Relations of Grapevines Grown in Three Different Conditions

Diurnal and seasonal changes in the leaf water potential (), stomatal conductance (g _s), net CO₂ assimilation rate (P _N), transpiration rate (E), internal CO₂ concentration (C _i), and intrinsic water use efficiency (P _N/g _s) were studied in grapevines (Vitis vinifera L. cv. Touriga Nacional) growing in low, moderate, and severe summer stress at Vila Real (VR), Pinhão (PI), and Almendra (AL) experimental sites, respectively. In VR and PI site the limitation to photosynthesis was caused more by stomatal limitations, while in AL mesophyll limitations were also responsible for the summer decline in P _N.     

极端干旱区疏叶骆驼刺叶绿素荧光对人工水分干扰的响应特征

选取塔里木河下游天然植被恢复示范区的疏叶骆驼刺(Alhagi sparsifolia Shap.)为研究对象,测定每年引水灌溉2次(每次0.42m3/m2)、1次和不灌溉(CK)处理下疏叶骆驼刺的实际光化学量子产量(ΦPSⅡ)、电子传输速率(ETR)和光化学猝灭系数(qP)等叶绿素荧光参数及其叶水势变化,探讨疏叶骆驼刺对人工水分干扰的叶绿素荧光响应特征。结果表明:(1)随着灌溉量的减少,疏叶骆驼刺叶水势呈显著降低的趋势,并在CK下达到最低。(2)同期疏叶骆驼刺qP、ΦPSⅡ、ETR、最大光量子产量(Fv/Fm)、叶绿素含量和光饱和点均随着灌溉量的减少呈先增加后降低的趋势,非光化学淬灭系数(NPQ)和调节性能量耗散(YNPQ)则呈先降低后增加的趋势。(3)与每年1次灌溉量处理相比,不灌溉和每年2次的灌溉量处理下疏叶骆驼刺发生了光抑制,光能捕获效率与光化学反应能量下降,热耗散能力提高。研究认为,灌溉量过高(每年2次,0.84m3/m2)或不灌溉均会限制疏叶骆驼刺光化学效率和光和活性,适时适量的(春季灌水1次,0.42m3/m2)水分补给更有利于疏叶骆驼刺适应干旱胁迫并维持正常光合生长。     

An isoenzyme study in the genus Lotus (Fabaceae). Experimental protocols and genetic basis of electrophoretic phenotype

Summary An isoenzyme survey of some taxa in the genus Lotus (Fabaceae) was undertaken to increase the number of genetic markers available to breeders and to students of Lotus phylogeny. Twenty-one enzymes were examined using starch gel electrophoresis and nine buffer systems. Clear, consistent banding patterns were obtained for PGI, TPI, MDH, IDH (NADP), PGM, 6-PGDH, and ME. Clear but inconsistent banding patterns were obtained for FDP, G₃PDH (NADP), -EST, LAP, MDH, DIA, and NADHDH. Phenotypes of the seven consistently resolved enzyme systems were obtained for different tissues for each of several genotypes at different stages of development. Variation in enzyme phenotypes of the same individuals under different growth conditions indicated the presence of different isozymic forms of these enzymes. Shoot tissue of plants over 6 weeks of age was found to be suitable material for further genetic studies, since phenotype for this tissue was constant despite changes in growing conditions. A formal genetic analysis of segregation and/or recombination of allozymes for the enzymes PGM, TPI, MDH, IDH, and 6-PGDH was undertaken. Isoenzyme phenotypes were examined for the diploids L. alpinus Schleich., L. burttii Sz. Borsos, L. conimbricensis Brot., L. ornithopodioides L., L. tennis Waldst. et Kit., and L. uliginosus Schkuhr; and for the diploid interspecific hybrids L. alpinus x L. conimbricensis, L. burttii x L. ornithopodioides, and L. japonicus x L. alpinus. Several new loci were identified for Lotus, namely, Idh1, Idh2, Mdh3, Pgi1, Pgi2, Tpi1, Tpi2, and 6-Pdgh1. Duplications of loci of IDH, MDH, PGI, and 6-PGDH were detected in the diploid (2n=12) interspecific hybrid L. japonicus x L. alpinus.     

Photosynthesis and Chlorophyll Fluorescence in Two Hybrids of Sorghum under Different Nitrogen and Water Regimes

In two hybrids of sorghum (Sorghum bicolor Moench.), C51 and C42, high nitrogen concentration (HN) increased net photosynthetic rate (PN), stomatal conductance (gs), and transpiration rate (E) of well watered (HW) plants. Water stressing (LW plants) resulted in low PN, gs, and E in both hybrids, but the values were still higher in HN plants as compared to low nitrogen-grown (LN) plants. Intercellular CO2 concentration (Ci) increased in droughted plants. This increase was much higher in LN plants as compared to HN plants. Instantaneous water use efficiency was lower in LN plants as a consequence of a greater effect of water stress on photosynthesis. Leaf water potential was reduced by water stress in all treatments. Analysis of chlorophyll a fluorescence at room temperature showed that photosystem 2 (PS2) was rather tolerant to the water stress imposed. Water stress caused a slight decrease in the efficiency of excitation capture by open PS2 reaction centres (Fv/Fm). The in vivo quantum yield of PS2 photochemistry (PS2) and the photochemical quenching coefficient (qP) were slightly reduced, while the nonphotochemical quenching coefficient (qN) was increased under the water stress. However, in hybrid C42 these characters were little or not affected by the water stress.