Contribution of microscopic techniques to anatomical and morphological knowledge on Styrax officinalis L

The aim of this study was to precise anatomical and morphological features of the species Styrax officinalis with the help of current microscopic techniques, those features being of interest as valuable taxonomic characters. Typical hairy structures were observed on all surfaces of the aerial organs and their location, density and size were specified. Moreover, we demonstrated the occurrence of secretory glands in the leaf blades. These structures were revealed for the first time for this species.     

Occurrence of endodermis with a casparian strip in stem and leaf

It is well known that an endodermis with casparian strip always occurs in roots, but few people are aware that it also occurs in stems and leaves of some vascular plants. The rather sparse literature on endodermis in aerial organs was last included in a review in 1943. The present compilation, which does not consider hydathodes, nectaries, or other secretory structures, emphasizes distribution of cauline and foliar endodermis with casparian strip. It occurs unevenly among major taxa: quite common in rhizomes and leaves among pteridophyte groups, with exceptions; absent in gymnosperm stems but found in leaves at least among some conifers; in stems of at least 30 mostly herbaceous angiosperm families, but far less common in leaves, where it is mostly reported from petioles. Etiolation can induce casparian strips in stems and petioles of some herbaceous plants, but results from leaf blades are questionable. There are recent reports of an endodermis with casparian strip in leaves of both woody and herbaceous taxa. The physiological function, if any, of a casparian strip in aerial organs remains unknown.     

On the interactions of histone H4 and H4 peptides with DNA. Electrooptical, hydrodynamic and electron microscopy studies

The interactions of DNA with histone H4 and with its fragments N-H4 (1-84) and C-H4 (85-102) have been studied by using electrooptical techniques, viscosity and electron microscopy. Electron microscopy reveals that histone H4 induces a large folding of DNA molecules : this is in agreement with electrooptical measurements which indicate that, with the increase of their ratio, H4/DNA complexes undergo a gradual process of condensation. Viscosity measurements show that complexes at ratios up to 0.20-0.25 become more rigid as compared to DNA. It appears that C-H4, and not the N-H4 fragment, causes a great distorsion to the structure of DNA, accompanied by an increase of rigidity at ratios up to 0.20-0.25, as occurs for H4/DNA complexes. Electrooptical studies of C-H4/DNA complexes show, along a range of histone/DNA ratios, an important permanent dipole component. These effects reveal a particular mode of interaction of C-H4 with DNA, indicating that some charged residues of the peptide are kept distant enough from the DNA backbone. As no dipole character, in addition to that shown for DNA, has been detected for H4/DNA complexes, it is concluded that the conformation of the H4 molecule modifies to some extent the interaction of the C-terminal region. Our results show that this histone, and particularly its C-terminal region, is important as a determinant factor in the folding of DNA within artificial complexes.     

Evaluation of the resistance to two nematodes: Radopholus similis and Meloidogyne spp. in four banana genotypes in Morocco

Radopholus similis and Meloidogyne spp. are the main nematode parasites of banana plants grown under plastic shelters in Morocco. A test was made in pots to evaluate the resistance of four genotypes of banana to these nematodes. Infection by Meloidogyne spp. brought about an increase in root weight in all banana plants tested because of gall formation. The inoculation of R. similis produced a reduction in length and diameter of the pseudo-trunk as well as in root and aerial mass in all genotypes. Pisang jari buaya showed the significantly lowest number of Meloidogyne nematodes per 10 g of roots, whereas for R. similis, the significantly smallest numbers were obtained in Pisang berlin and Pisang jari buaya. Therefore, Pisang jari buaya was the only banana genotype studied to show some degree of resistance to both nematodes.     

Inibizione della nodulazione radicale nel pisello meteor come conseguenza del trattamento nictofasico intermittente con luce rosso-estrema

Abstract

INHYBITION OF NODULATION IN METEOR PEA, BY NICTOPHASIC TREATMENT WITH FAR-RED RADIATION. — A remarkable inhybiting effect of far-red light (given to the aerial part of the plants as a flash befor and during the nictophase) on Pea root nodulation, has been achivied through some preliminary experiments. The relations between irradiated aerial parts and the activities of the underground organs in general, are being studied in the picture of photo-chromoperiodism.

Relations with the action of gibberellic acid (GA) are preliminary attempted. The inhibiting action of GA is far less striking in comparison with that of far-red radiation. Kinetin favores, at some extent, the nodulation process.     

Shoot atmospheric contact is of little importance to aeration of deeper portions of the wetland plant Meionectes brownii; submerged organs mainly acquire O2 from the water column or produce it endogenously in underwater photosynthesis

Partial shoot submergence is considered less stressful than complete submergence of plants, as aerial contact allows gas exchange with the atmosphere. In situ microelectrode studies of the wetland plant Meionectes brownii showed that O₂ dynamics in the submerged stems and aquatic roots of partially submerged plants were similar to those of completely submerged plants, with internal O₂ concentrations in both organs dropping to less than 5 kPa by dawn regardless of submergence level. The anatomy at the nodes and the relationship between tissue porosity and rates of O₂ diffusion through stems were studied. Stem internodes contained aerenchyma and had mean gas space area of 17.7% per cross section, whereas nodes had 8.2%, but nodal porosity was highly variable, some nodes had very low porosity or were completely occluded (ca. 23% of nodes sampled). The cumulative effect of these low porosity nodes would have impeded internal O₂ movement down stems. Therefore, regardless of the presence of an aerial connection, the deeper portions of submerged organs sourced most of their O₂ via inwards diffusion from the water column during the night, and endogenous production in underwater photosynthesis during the daytime.     

Effect of CCC on the growth of roots of Vitis vinifera L.

Summary When plants of Vitis vinifera L. were grown in solution cultures containing (2-chloroethyl)trimethylammonium chloride (CCC), roots became shorter and thicker than those of untreated control plants. The effect of CCC on vine roots could be counteracted by gibberellic acid simultaneously applied either to the solution cultures or to aerial organs of the plant.     

Monoacylglycerols are components of root waxes and can be produced in the aerial cuticle by ectopic expression of a suberin-associated acyltransferase

The interface between plants and the environment is provided for aerial organs by epicuticular waxes that have been extensively studied. By contrast, little is known about the nature, biosynthesis, and role of waxes at the root-rhizosphere interface. Waxes isolated by rapid immersion of Arabidopsis (Arabidopsis thaliana) roots in organic solvents were rich in saturated C18-C22 alkyl esters of p-hydroxycinnamic acids, but also contained significant amounts of both alpha- and beta-isomers of monoacylglycerols with C22 and C24 saturated acyl groups and the corresponding free fatty acids. Production of these compounds in root waxes was positively correlated to the expression of sn-glycerol-3-P acyltransferase5 (GPAT5), a gene encoding an acyltransferase previously shown to be involved in aliphatic suberin synthesis. This suggests a direct metabolic relationship between suberin and some root waxes. Furthermore, when ectopically expressed in Arabidopsis, GPAT5 produced very-long-chain saturated monoacylglycerols and free fatty acids as novel components of cuticular waxes. The crystal morphology of stem waxes was altered and the load of total stem wax compounds was doubled, although the major components typical of the waxes found on wild-type plants decreased. These results strongly suggest that GPAT5 functions in vivo as an acyltransferase to a glycerol-containing acceptor and has access to the same pool of acyl intermediates and/or may be targeted to the same membrane domain as that of wax synthesis in aerial organs.     

Characteristic Trichomes and Indumentum Specialization in African and European Parasitic Scrophulariaceae

Trichomes and their distribution patterns have been observed in the aerial parts of plants of the genera Striga, Buchnera, Rhamphicarpa, Euphrasia, Melampyrum and Rhinanthus, using both light (LM) and scanning electron microscopy (SEM). All trichomes belong to the multicellular, uniseriate category and can be classified as glandular and nonglandular types. On nearly all organs, the two types can be observed side by side. Apart from a large group of ubiquitous trichomes, some characteristic trichome types are reported; they are restricted either to chlorophyllous organs (foliage leaves, bracts, calyx and stem) or to the corolla. In some nonglandular trichomes mineral deposits have been found. Other morphological and anatomical trichome features are discussed with regard to their possible function.     

Structural investigation of the glandular trichomes of <Emphasis Type="Italic">Salvia argentea</Emphasis>

The morphology, anatomy and distribution of glandular trichomes on the aerial organs of Salvia argentea L. has been investigated. Two morphologically distinct types of glandular trichomes were determined. Capitate glandular trichomes forming a base 1–7 celled, a stalk 1–5 celled or no stalk and a head uni- or bicellular had various types. In capitate trichomes, the neck cell that has an important role especially for xeroformic plants, acting to prevent the backflow of secreted substance through the apoplast has been distinctively observed in the investigated species. The capitate trichomes were present abundantly on all aerial organs of S. argentea. Peltate glandular trichomes had a large secretory head forming 1–5, 8 central and 8–10, 12, 14 peripheral cells. Peltate trichomes are present on all aerial organs, except petiole, being the most abundant on calyx and corolla. Results were shown by tables and photographs.     

The MIXTA-like Transcription factor MYB16 is a major regulator of cuticle formation in vegetative organs

Cuticle secreted on the surface of the epidermis of aerial organs protects plants from the external environment. We recently found that Arabidopsis MIXTA-like R2R3-MYB family members MYB16 and MYB106 regulate cuticle formation in reproductive organs and trichomes. However, the artificial miRNA (amiRNA)-mediated knockdown plants showed no clear phenotypic abnormality in vegetative tissues. In this study, we used RNA interference (RNAi) targeting MYB16 to produce plants with reduced expression of both MYB16 and MYB106. The rosette leaves of RNAi plants showed more severe permeable cuticle phenotypes than the myb106 mutants expressing the MYB16 amiRNA in the previous study. The RNAi plants also showed reduced expression of cuticle biosynthesis genes LACERATA and ECERIFERUM1. By contrast, expression of a gain-of-function MYB16 construct induced over-accumulation of waxy substances on leaves. These results suggest that MYB16 functions as a major regulator of cuticle formation in vegetative organs, in addition to its effect in reproductive organs and trichomes.     

N, P, and C stoichiometry of Eranthis hyemalis (Ranunculaceae) and the allometry of plant growth

We report the nitrogen (N), phosphorus (P), and carbon (C) stoichiometry for each of the five organ-types (leaves, aerial stems, reproductive organs, roots, and tubers) of 17 actively growing Eranthis hyemalis plants differing in size (as measured in g C). We also report the N, P, and C stoichiometry of 20 winterized tubers, which are the only perennial organs of this species. Comparisons between whole-plant and winterized N/C and P/C levels indicate that N was resorbed from aerial organs and stored in tubers by the end of the growing season. Leaves were substantial reservoirs for N and P. With few exceptions, N scaled isometrically with respect to C for each organ-type, whereas P scaled as the 3/4 power of C. Thus, N is proportional to P(3/4), which is proportional to C regardless of organ-type. Additionally, annual growth rate G of shoots (leaves and aerial stems) scaled as the -3 power of leaf N/P quotients such that G was proportional to the 3/4 power of leaf P. We suggest that these scaling relationships (together with previously reported allometric trends across herbaceous species) show that growth is constrained by organ-specific N and P allocation patterns (presumably to proteins and ribosomes, respectively).     

In vitro culture and fructan production by Vernonia herbacea (Asteraceae)

Vernonia herbacea is a native species from the Brazilian Cerrado that accumulates about 80 % of inulin-type fructans in the underground reserve organs, the rhizophores. This work aimed at establishing a protocol for in vitro culture of V. herbacea, using seeds (achenes) and leaf discs as explants. Following germination and seedling growth, stem nodes from 6-month-old in vitro germinated plants were isolated and incubated on culture medium free of growth regulators for plant propagation and rhizophore formation. Fructan content and composition were evaluated in leaves, stems, roots and rhizophores from plants grown in vitro and compared with those of greenhouse-grown plants, in order to evaluate inulin production in vitro. Fructan contents of aerial organs and roots from in vitro plants were higher, compared with greenhouse plants, while in rhizophores, the opposite was observed. High performance anion exchange chromatography/pulsed amperometric detection profiles revealed the presence of the inulin homologous series in the aerial organs exclusively for in vitro plants, while in roots and rhizophores, this series was detected in plants grown in both conditions. These results indicate a modification in the source/sink ratio, leading to changes in the distribution of carbohydrates in in vitro plants. The leaf disc cultures on medium supplemented with indole-3-butyric acid induced the formation of roots (0.24, 0.49 µM) and friable callus (2.46 µM), while 6-benzylaminopurine (from 1.1 through 4.43 µM) induced compact callus. However, no shoot formation was observed. The use of seeds allowed the establishment of a protocol for in vitro culture and provides a model system for a better understanding of fructan metabolism in V. herbacea.     

Studies on the growth and development of Oxalis latifolia

The growth and development of Oxalis latifolia was assessed on outdoor-grown potted plants raised from bulbs. Three main phases of growth appeared to be correlated with major physiological developments in the aerial and subterranean organs. Establishment (weeks 1 – 5) was characterised by a slow gain in plant dry weight accompanied by high relative growth rate (RGR) values for individual plant organs. The second phase of growth (weeks 6 – 12) was reproductive, as stolons grew and initiated bulbils at the apices. Bulbils had the capacity to produce their own shoot system and ultimately some primary bulbils supported secondary bulbils. Dry matter accumulation was in the order: bulbils > peduncles > leaves > petioles > stolons = roots > parent bulb. The RGR of individual plant organs declined together with the net assimilation (NAR) rates and the leaf area ratio of the shoots during the reproductive phase and beyond into the senescence phase (week 13 onwards). The results are discussed in relation to the problem of achieving weed control via cultural and herbicide treatments.     

植物表皮毛研究进展

表皮毛是大多数植物地上部分表皮组织所延伸出来的一种特化的毛状结构附属物。表皮毛在植物表皮层和环境间构筑了一道天然的物理屏障, 不但对植物的生长发育具有重要意义, 而且还具有非常高的应用价值和经济价值。近几年, 研究者从不同植物中不断克隆出新的表皮毛发育相关基因, 在揭示植物调控表皮毛生长发育的分子机制方面取得很大进展。该文综述了植物表皮毛的最新研究进展, 并展望了植物表皮毛的研究方向及应用开发价值。     

Overexpression of Arabidopsis ECERIFERUM1 promotes wax very-long-chain alkane biosynthesis and influences plant response to biotic and abiotic stresses

Land plant aerial organs are covered by a hydrophobic layer called the cuticle that serves as a waterproof barrier protecting plants against desiccation, ultraviolet radiation, and pathogens. Cuticle consists of a cutin matrix as well as cuticular waxes in which very-long-chain (VLC) alkanes are the major components, representing up to 70% of the total wax content in Arabidopsis (Arabidopsis thaliana) leaves. However, despite its major involvement in cuticle formation, the alkane-forming pathway is still largely unknown. To address this deficiency, we report here the characterization of the Arabidopsis ECERIFERUM1 (CER1) gene predicted to encode an enzyme involved in alkane biosynthesis. Analysis of CER1 expression showed that CER1 is specifically expressed in the epidermis of aerial organs and coexpressed with other genes of the alkane-forming pathway. Modification of CER1 expression in transgenic plants specifically affects VLC alkane biosynthesis: waxes of TDNA insertional mutant alleles are devoid of VLC alkanes and derivatives, whereas CER1 overexpression dramatically increases the production of the odd-carbon-numbered alkanes together with a substantial accumulation of iso-branched alkanes. We also showed that CER1 expression is induced by osmotic stresses and regulated by abscisic acid. Furthermore, CER1-overexpressing plants showed reduced cuticle permeability together with reduced soil water deficit susceptibility. However, CER1 overexpression increased susceptibility to bacterial and fungal pathogens. Taken together, these results demonstrate that CER1 controls alkane biosynthesis and is highly linked to responses to biotic and abiotic stresses.     

Some factors influencing the uptake and distribution of selenite in the bean plant (Phaseolus vulgaris)

Three hours after the absorption of selenite by the roots ofPhaseolus vulgaris a major part of the Se accumulates in the roots while the fraction conveyed towards the aerial organs is unevenly distributed. Uptake and distribution are enhanced when plants are kept in darkness or when the nutritive solution is supplied with glucose, suggesting an active transport of selenite. However, when roots are soaked in a low temperature solution or supplied with metabolic inhibitors, the level of Se decreased by about 35% in the roots and in the aerial organs. So, part of the selenite enters the roots by diffusion, while another part is metabolically linked. Sugar translocated from the leaves is implicated as a co-transport-substance for selenite. Antibiotics, such as gramicidin, synthetised by micro-organisms, can also increase the level of Se within the bean plant.     

Mobilisation of nutrients and transport via the xylem sap in a shrub (Ligustrum ovalifolium) during spring growth: N and C compounds and interactions

In open-field soilless culture there can be great deal of leaching, particularly in rainy springs. Ligneous plants have the capacity to store large quantities of nutrients in perennial organs. Knowledge of the plant's internal nutrient mobilisation during spring to supply growing organs could lead to reduction of fertiliser application. To quantify the fraction of storage mobilisation available for growth of new organs during spring, Ligustrum ovalifolium shrubs were grown for 2 years with or without fertilisation in the second spring. Nitrogen (N) absorption and N and carbon (C) mobilisation from storage were followed during spring growth via the sap quality. A mathematical combination of the sap composition with flow velocity provided the transported quantities of N and C. Nitrogen and C mobilisation towards new shoots took place during all the spring growth from bud break onwards. In unfertilised plants, C was mobilised primarily as sugars (stachyose, mannose and sucrose) and starch. In fertilised plants, the same sugars were transported in the xylem sap, but at lower concentrations. Stachyose concentration was lower in fertilised than in unfertilised plants and decreased during spring growth. Nitrogen was transported in the xylem sap mainly as amino acids in both fertilisation treatments. Glutamine was the predominant form at bud break and during shoot elongation. In fertilised plants, arginine became predominant after shoot elongation, and was related to low C availability. The interactions of N with C are discussed; specifically, insufficient availability of N limits the use of C, more of which is directed to aerial organs by sap flow.     

Effects of ascochyta blight (Mycosphaerella pinodes Berk. & Blox.) on biomass production, seed number and seed weight of dried-pea (Pisum sativum L.) as affected by plant growth stage and disease intensity

The effects of ascochyta blight due to Mycosphaerella pinodes on biomass production, seed number and seed weight according to physiological stage and disease intensity were examined. Pea plants were grown in a glasshouse and inoculated with various concentrations of conidia before flowering, at flowering of the second fructifer node (FLO2), at the start of seed filling of the first fructifer node (FSSA1) or the second fructifer node (FSSA2). Uninoculated plants were used as controls. Whatever the stage of inoculation (FLO2 or FSSA2), the disease reduced plant growth and the decrease depended on disease intensity on foliar organs. The seed number was reduced for plants inoculated before flowering, at FLO2 and at FSSA1 and the reduction was linked to disease intensity on foliar organs. At each node, seed number was reduced if the disease occurred before FSSA of the node. The mean seed weight per plant was decreased in plants inoculated at FSSA1 and FSSA2 and the higher the disease intensity on aerials organs, the greater was the reduction of the seed weight. For individual nodes, only inoculations after the beginning of seed filling had a negative effect on mean seed weight at harvest. We found that the decrease of seed number induced by the disease was proportional to aerial biomass production before the end of the period of seed production.