Seed morphology ofEuphorbia sectionTithymalopsis (Euphorbiaceae) and related species

Light and scanning microscopies were used to evaluate the sectional boundary of 17 species included by various authors inEuphorbia sectTithymalopsis. Based on seed shape, surface ornamentation, and mucilage formation, five seed morphological types were recognized in North American sectionTithymalopsis and related species. These results did not provide added support for recent treatment of the sectTithymalopsis s.s. However, a close relationship was suggested among species of theTithymalopsis subsectionCorollatae. In addition, including species from subsectionsInnocuae, Ipecacuanhae, andSphaerorhizae within sectTithymalopsis could not be justified, based on seed morphological data.     

Ecological wood anatomy of NepaleseRhododendron (Ericaceae). 1. Interspecific variation

The relationship of selected wood anatomical characters of NepaleseRhododendron with stem diameter, plant height, altitude, and plant form was investigated. We studied one to three specimens each of 26 species: five species each of trees and subtrees I, three species of subtrees II, and 13 species of shrubs. Multiple regression analysis and actual distribution of character values show that pore characters and multiseriate ray ratio have a stronger correlation with stem diameter than altitude; that pore density, vessel element length, fiber-tracheid length, and multiseriate ray density and width are equally related to altitude and stem diameter, or to altitude and plant height; and that bar number, and multiseriate ray area and height have a stronger connection with altitude. Among the characters, average pore area is most strongly correlated with stem diameter and increases exponentially as diameter increases. For wood structure of NepaleseRhododendron, 17 to 63 % of the variation is affected by non-anatomical factors. The general trends in wood structure of NepaleseRhododendron show that trees and subtrees form one continuous unit whereas shrubs form another that often has wider ranges of variation.     

Peroxidase activities in relation to plant height and grain weight in bread wheat (Triticum aestivum L.)

Summary The relationship of peroxidase activity with plant height and grain weight has been studied in seven different varieties of bread wheat belonging to diverse genotypes, and their F₁ crosses. The association between plant height and peroxidase activity was highly significant and negative. Based on the similarity index values of peroxidase isoenzymes, the seven wheat genotypes could be classified into two groups: the first group consisting of triple and quadruple dwarf varieties and the other of tall, single and double dwarf. A negative correlation between peroxidase activity and grain weight was also observed. However, the results of this study indicate a possibility of developing a dwarf plant type with low peroxidase activity and well filled grains.     

Ecophysiology and distribution of the endemic leafless spurgeEuphorbia aphylla and the introducedE. tirucalli (Euphorbiaceae,Euphorbia sect.Tirucalli) in the Canary Islands

The leafless spurgeEuphorbia aphylla (Euphorbiaceae), an endemic species restricted to several of the Canary Islands where it inhabits coastal and arid localities, expresses Crassulacean Acid Metabolism (CAM) when it is subjected to summer drought. A flexible CAM is consistent with the general ecology of the species. It is the only member of sect.Tirucalli native to the Canary Islands and is at the north-western edge of the section's biogeographical range. The other members of the section have a paleotropic distribution and are found throughout Africa. Many of them are regarded as obligate CAM plants, includingE. tirucalli which was used as a comparison in ecophysiological experiments examining the response ofE. aphylla to drought and temperature.     

Quantitative trait loci for lodging resistance,plant height and partial resistance to mycosphaerella blight in field pea (Pisum sativum L.)

With the development of genetic maps and the identification of the most-likely positions of quantitative trait loci (QTLs) on these maps, molecular markers for lodging resistance can be identified. Consequently, marker-assisted selection (MAS) has the potential to improve the efficiency of selection for lodging resistance in a breeding program. This study was conducted to identify genetic loci associated with lodging resistance, plant height and reaction to mycosphaerella blight in pea. A population consisting of 88 recombinant inbred lines (RILs) was developed from a cross between Carneval and MP1401. The RILs were evaluated in 11 environments across the provinces of Manitoba, Saskatchewan and Alberta, Canada in 1998, 1999 and 2000. One hundred and ninety two amplified fragment length polymorphism (AFLP) markers, 13 random amplified polymorphic DNA (RAPD) markers and one sequence tagged site (STS) marker were assigned to ten linkage groups (LGs) that covered 1,274 centi Morgans (cM) of the pea genome. Six of these LGs were aligned with the previous pea map. Two QTLs were identified for lodging resistance that collectively explained 58% of the total phenotypic variation in the mean environment. Three QTLs were identified each for plant height and resistance to mycosphaerella blight, which accounted for 65% and 36% of the total phenotypic variation, respectively, in the mean environment. These QTLs were relatively consistent across environments. The AFLP marker that was associated with the major locus for lodging resistance was converted into the sequence-characterized amplified-region (SCAR) marker. The presence or absence of the SCAR marker corresponded well with the lodging reaction of 50 commercial pea varieties.Communicated by H. F. Linskens     

Meiotic studies ofElymus nutans andE. jacquemontii (Poaceae,Triticeae) and their hybrids withPseudoroegneria spicata and seventeenElymus species

Hybridizations ofElymus nutans andE. jacquemontii were carried out with one species ofPseudoroegneria (S genome), and 20Elymus species, each containing either of the SH, SY, SYH, or SYW genomes. Chromosome configurations were analysed at metaphase I of the two target taxa and their interspecific hybrids. It is concluded that (i)E. nutans is an allohexaploid containing the SYH genomes, andE. jacquemontii is an allotetraploid having the SY genomes; (ii) the genomic affinity is associated with the geographic distance between the species studied; (iii) minor genomic structural rearrangements have occurred within the hexaploid taxon ofE. nutans.     

The plant growth regulator activity of the fungicide,epoxiconazole, on Galium aparine L. (cleavers)

The plant growth regulator activity of epoxiconazole, a new triazole fungicide, was investigated by time-course, dose-response and histology experiments with Galium aparine L. (cleavers). Seven days after treatment with 125g ai ha^–1 epoxiconazole (field rate), plant height was reduced by 43%. After seventeen days, leaflet area was reduced by 27% but leaflet fresh weight was not significantly influenced. This was partly because leaflet thickness had increased by 20% following epoxiconazole application. Chlorophyll concentrations were also increased on a unit area basis. Examination of leaflet anatomy showed that epoxiconazole elongated palisade, spongy mesophyll and upper epidermal cells. For example, 125g ai ha^–1 caused a 35% increase in the length of spongy mesophyll cells. Epoxiconazole also prevented cell separation as there were significantly more palisade and spongy mesophyll cells per unit area than in leaflets sprayed with water. Stem development was reduced and 125g ai ha^–1 inhibited the elongation of pith cells in stem tissue by 53%. However, the simultaneous application of gibberellin A₃ (GA₃) with epoxiconazole resulted in stem elongation similar to that of control plants. These observations are consistent with the expected effects following the inhibition of cytochrome P-450 dependent enzyme activity.Abbreviations GA₃ gibberellin A₃ - g ai ha^–1 grams of active ingredient per hectare - L ha^–1 litres per hectare - PPFD photosynthetic photon flux density - RH relative humidity - SE standard error     

青藏高原三种优势植物生物量分配的变化规律

该研究利用4个由高到低不同海拔的同质园实验,以青藏高原高寒草地优势植物垂穗披碱草(Elymus nutans)、矮嵩草(Kobresia humilis)和珠芽蓼(Polygonum viviparum)为对象,分析了植物个体根、茎、叶生物量分配及根冠比的变化规律及影响因素。结果表明:(1)植物个体根、茎、叶质量比和根冠比具有显著的种间差异;与垂穗披碱草和珠芽蓼相比,矮嵩草具有显著较高的根质量比而叶、茎质量比较低,所以其根冠比较高。(2)在向低海拔移栽的过程中,珠芽蓼叶质量比保持不变,茎质量比显著降低而根质量比显著升高,根冠比表现出显著上升的趋势;垂穗披碱草则相反,即叶、茎质量比显著升高而根质量比显著降低,根冠比表现出显著下降的趋势;矮嵩草根、茎、叶质量比和根冠比则无显著变化。(3)随着海拔降低,年均气温明显升高而年均降雨量明显降低,且在植物个体种源地和土壤基质保持一致的条件下,向低海拔移栽过程中温度是导致珠芽蓼根、茎、叶生物量分配及根冠比变化的重要因素,而水分是垂穗披碱草根、茎、叶生物量分配及根冠比变化的重要驱动因素;矮嵩草根、茎、叶生物量分配及根冠比受其遗传因素影响较大。因此,在将来暖干化的背景下,青藏高原高寒草地植物生物量的分配将会发生改变,导致它们对资源(光照、水分和土壤养分)获取和利用的变化而改变它们的种间关系,从而影响群落的物种多样性与组成,最终可能导致生态系统功能的变化。     

Reexamination of sectional classification in far easternEuphorbia subgenusEsula (Euphorbiaceae) using morphological and phenolic data

Reexamining the classification proposed by Hurusawa, the phylogeny of Far EasternEuphorbia subgenusEsula was analyzed using thirteen morphological and seventeen phenolic compound data. These data were analyzed independently and in combination using PAUP under the assumptions of Fitch parsimony. Ten species, comprised of three sections and five subsections within Far EasternEuphorbia subg.Esula and one outgroup from subg.Chamaesyce, were used as terminal taxa. The phylogenetic results did not support the sectional classifications within subg.Esula proposed by Hurusawa. SectionDecussatae was nested in the paraphyletic sectEsula in all of the analyses, and the relationship of sectHelioscopiae was equivocal among data sets. The disagreement of data sets over the placement ofEuphorbia ebracteolata is probably due to a hybrid origin of the species and missing phenolic data forE. pallasii. A sister-group relationship of the Korean endemicE. fauriei with the widespreadE. pekinensis was strongly supported by the morphological and phenolic data.     

Polyploidy and habitat differentiation in Dactylis glomerata L. from Galicia (Spain)

Summary The microdistribution of diploid and tetraploid plants of Dactylis glomerata L. was examined and related to their immediate environment in several sites in central Galicia, where morphologically indistinguishable individuals of both ploidies grow in sympatry. The two related cytotypes differed in habitat preference. Diploids were mainly confined to the low-density forest-floor habitat in woodlands of mostly ancient origin, whereas tetraploids were widespread in varied habitats but clearly predominant in open areas, particularly in disturbed anthropic sites. The in situ comparison of plant performance showed that where plants of each ploidy were more common they produced more tillers, panicles and seeds. This habitat preference closely reflected differences in life-history characteristics. The tetraploids had an early and short flowering time almost always completed before the aestival drought, whereas the diploids began to flower several weeks later and flowered throughout the drought. Comparisons along artificial gradients of soil water availability and light transmittance indicated that the cytotypes had distinct physiological requirements which probably originated in metabolic and more general genetic differentiation and could be directly attributable to ploidy. Habitat differentiation increases the species' colonizing ability. It also amplifies divergence in reproductive strategy between diploids and tetraploids, which reduces ineffective crossing between cytotypes and thereby permits them to coexist in sympatry. The effect of hybridization at the polyploid level on the differentiation between cytotypes was assessed from the recent introduction of a foreign tetraploid entity into the study area. Hybridization between the two distinct tetraploids was found to increase habitat differentiation between the diploids and the tetraploids, but the major part of this differentiation is probably attributable to ploidy itself.     

Genome analysis ofElymus angulatus andE. patagonicus (Poaceae) and their hybrids with N. and S. AmericanHordeum spp.

The results of genome analysis of five hybrids, viz.Elymus patagonicus ×Hordeum procerum, E. patagonicus ×H. tetraploidum, E. angulatus ×H. jubatum, E. angulatus ×H. lechleri, andE. angulatus ×H. parodii, are reported. The genomic constitution ofHordeum tetraploidum andH. jubatum is best given as H₁H₁H₂H₂, ofH. lechleri andH. parodii as H₁H₁H₂H₂H₄H₄, ofH. procerum as H₁H₁H₂H₂H₃H₃, and ofElymus patagonicus andE. angulatus as SSH₁H₁H₂H₂.     

Comparison of the Giemsa C-banded and N-banded karyotypes of twoElymus species,E. dentatus andE. glaucescens (Poaceae: Triticeae)

The karyotypes ofElymus dentatus from Kashmir andE. glaucescens from Tierra del Fuego, both carrying genomesS andH, were investigated by C- and N-banding. Both taxa had 2n = 4x = 28. The karyotype ofE. dentatus was symmetrical with large chromosomes. It had 18 metacentric, four submetacentric and six satellited chromosomes. The karyotype ofE. glaucescens resembled that ofE. dentatus, but a satellited chromosome pair was replaced by a morphologically similar, non-satellited pair. The C-banding patterns of both species had from one to five conspicuous and a few inconspicuous bands per chromosome. N-banding differentiated the chromosomes of the constituent genomes by producing bands in theH genome only. TheS genomes of both species were similar with five metacentric and two satellited chromosomes having most conspicuous C-bands at telomeric and distal positions. They resembled theS genome of the genusPseudoroegneria. TheH genomes had four similar metacentric and two submetacentric chromosomes. The seventhH genome chromosome ofE. dentatus was satellited, that ofE. glaucescens nonsatellited, but otherwise morphologically similar. The C-bands were distributed at no preferential positions. TheH genome ofE. dentatus resembles theH genomes of some diploidHordeum taxa.     

In vitro regeneration from excised leaves of Flaveria trinervia (Sprengel) C. Mohr

Flaveria trinervia (Compositae) leaves are used for the treatment of jaundice and fever. From the leaf callus cultures regeneration of plantlets has been achieved. The results showed that BAP greatly stimulated the bud formation in concentrations ranging from 2–5 mg l^–1 than at very low concentrations (0.2–1.0 mg l^–1). Roots developed on the regenerated shoots, over a range of treatments, but were most prolific in the medium containing 1 mg l^–1 IAA. Histological observations revealed that cultured spongy cells of the mesophyll were greatly enlarged and underwent repeated cell divisions leading to the formation of hard nodular callus from which shoot buds differentiated. The shoots obtained were readily rooted and transplanted into glass houses. Cytological studies of the callus showed abnormalities such as bridges, endomitosis and multinucleolate conditions. Root tip squashes of the regenerated plants showed no variations and were diploid in chromosome number.Abbreviations 2,4-D 2,4-dichlorophenoxy acetic acid - NAA napthalene acetic acid - IAA indole acetic acid - BAP 6-benzyl aminopurine - Kn kinetin     

Ultrastruktur und Entwicklungsgeschichte des Pollenkitts vonEuphorbia cyparissias,E. palustris undMercurialis perennis (Euphorbiaceae)

Development, fine structure and distribution of pollenkitt is investigated inEuphorbia cyparissias, E. palustris, andMercurialis perennis. The predominantly anemophilousM. perennis produces a great amount of strictly homogeneous pollenkitt, which is deposited in the exine caves. In contrast to this and to all other angiosperms so far investigated, bothEuphorbia species produce large quantities of an extremely inhomogeneous and particular pollenkitt. Its ultrastructure is quite different, both during its development and after its deposition on the exine surface: Lipid particles with different electron density and size are wrapped in a strictly homogeneous electron transparent matrix. This can be considered as new and additional proof for the secondary entomophily ofEuphorbia.

     

In vitro organogenesis and plant regeneration from leaves of Solanum candidum Lindl,S. quitoense Lam. (naranjilla) and S. sessiliflorum Dunal

Adventitious shoots and roots were regenerated from leaf segments of 3 Solanum species: S. candidum Lindl., S. quitoense Lam. and S. sessiliflorum Dunal. Leaf explants differentiated shoots on modified MS medium supplemented with 23–163 M kinetin and 0–5.7 µM indoleacetic acid (IAA). Excised shoots were induced to form roots by transfer to media with benzyladenine (BA) and naphthaleneacetic acid (NAA) at 0.09 and 0.11 µM respectively for S. quitoense and 0.01 µM NAA for S. candidum and S. sessiliflorum. Adventitious roots were produced directly from leaf explants with 0–140 µM kinetin and 0–5.7 µM IAA in combination. Rooted plants were successfully established in the greenhouse.     

Somatic embryogenesis and plant regeneration from different wild diploid cotton (Gossypium) species

Calli were successfully induced from hypocotyls of eight wild diploid cotton species (Gossypium) on MSB (MS salts and B₅ vitamins) medium supplemented with 0.09 μM 2,4-D (2,4-dichlorophenoxyacetic acid) and 2.32 μM KT (kinetin). Plant growth regulator (PGR) combinations, adding GA₃ (Gibberellic acid), high inorganic salt stress, and PGR-free media were used to induce embryogenic calli from nonembryogenic calli. Embryogenic cultures were induced from G. aridum S. (D₄ genome), G. davidsonii K. (D₃-d genome), G. klotzschianum A. (D₃-k genome), G. raimondii U. (D₅ genome), and G. stocksii M. (E₁ genome). We then observed somatic embryogenesis in the five species while calli of G. africanum V. (A₁-2 genome), G. anomalum W. (B₁ genome), and G. bickii P. (G genome) remained nonembryogenic. Somatic embryogenesis was adjusted by changing sugar sources, regulating combinations of PGRs, and using cell suspension culture. Embryos at various developmental stages produced mature and germinating embryos when cultured on filter paper placed on the media containing different sugar sources. The utility of different sugar sources promoted globular embryos developing into cotyledonary stage and increased the frequency of cotyledonary embryos developing into normal plants. Normal plantlets were regenerated from G. davidsonii, G. klotzschianum, G. raimondii, and G. stocksii. Only abnormal plantlets were obtained in G. aridum. This work will contribute to broadening the number of regenerable cotton species and provide foundations for somatic hybridization in cotton to create new germplasm.     

Biomass allocation and growth responses of Scots pine saplings to simulated herbivory depend on plant age and light availability

This study experimentally analyses the response to simulated herbivory of juvenile Scots pine of two different ages in contrasting abiotic scenarios, focusing on the potential dual role of browsing ungulates: negative, by removing aerial biomass, and positive, by stimulating compensation capacity and providing nutrients by depositing their excrement. Compensation against herbivory was investigated by experimentally clipping a set of Scots pine (Pinus sylvestris L. nevadensis) juveniles, grown under different levels of light and nutrient availability. The responses analysed were survival, trunk-diameter growth, leader-shoot growth, increment in number of meristems, RGR, biomass of needles, shoots, root and whole plant, and root-to-shoot ratio. Clipping consistently resulted in a worse survival and performance of pines with respect to unclipped ones. From the factors analysed, light availability was responsible mainly for the variations in plant performance, while the addition of nutrients was much less important. Age was also important, with older pines showing in general better performance after clipping. Overall, clipping invariably had a negative effect on Scots pine, since none of the combinations of abiotic factors used resulted in overcompensation. However, the intensity on this negative effect proved quite variable, from almost an exact compensation in clipped older pines under full sunlight availability to very poor performance and high death probability in younger pines in shade. Scots pine cannot overcompensate after clipping, but, depending of the environmental conditions, the negative result of clipping varies from severe undercompensation to almost exact compensation. Also, small differences in sapling age can promote significant differences in sapling response to clipping and light environment.     

Pinnately ramified ensiform leaves in the genus Marathrum, (Podostemaceae-Podostemoideae)

The paper deals with the complex leaves of three species of the aquatic genus Marathrum (M. minutiflorum, M. rubrum and M. schiedeanum). It is shown that they represent pinnately ramified ensiform leaves. The dissection of the leaves contributes to surface enlargement and thus to improvement of their hydrophylls function. The ensiform structure is confirmed by the transverse position of the sheathing lower leaf zone and the subsequent intercalary elongational growth proceeding in the median plane towards the abaxial side of the leaf (upper leaf zone). The petiole continues into the rachis-like central axis of the blade from which pinnate-like segments diverge at the adaxial and abaxial edge of the ensiform blade. The segments give rise to tufts of clavate enations that end in long filaments. The filigree pinnately segmented ensiform leaves of Marathrum are interpreted as a further development of the fan-shaped and irregularly lobate ensiform leaves occurring in Mourera and Apinagia. Pinnately ramified ensiform leaves obviously evolved in convergence to the common type of pinnate leaves found in angiosperms.     

Genomic relationships of theElymus parviglumis,E. semicostatus,andE. tibeticus groups (Triticeae: Poaceae)

In order to investigate genomic relationships of tetraploidElymus species (all containing the SY genomes) among three morphological groups, i.e. theE. parviglumis, E. semicostatus, andE. tibeticus groups, interspecific hybridizations were carried out among representative species from the three groups. Chromosome associations at metaphase I were analysed in the interspecific hybrids, and genomic relationships of the species within and among the three groups were estimated. Hybridizations among species of the three groups were fairly easy to perform, but no general pattern for crossabilities among certain species or groups was obtained. All the hybrids were completely sterile. Meiotic pairing was moderately high, but ranges of chiasmata were observed in different hybrid combinations. There is no tendency for genomic affinities to be higher within groups than between the groups. Therefore, the meiotic data do not support the division of the SY-genome species into the three groups. However, there is a clear tendency that the differentiation of the SY genomes in the tetraploids is associated with the geographic distribution of the species.