Plagiotropic Shoot Research Articles

δ13C in above-ground and below-ground organs of Spinulum annotinum (Lycopodiaceae)

• 12 C and 13 C isotope abundance in S. annotinum has been investigated for the first time. • δ 13 C value in S. annotinum is lower than that reported in other C 3 plants. • Different above- and below-ground S. annotinum organs have distinct δ 13 C values. • δ 13 C values of S. annotinum are connected with local plant diversity. Physiological processes in plants and plant–environment interactions can be analysed from the composition of stable carbon isotopes ( 13 C/ 12 C). This ratio can be indicated using the δ (delta) notation. Substantial evidence has been published in recent years demonstrating that post-photosynthetic fractionation occurs in plants and leads to differences in 13 C-enrichment in heterotrophic (as compared with autotrophic) organs. Yet our understanding of processes leading to 13 C divergence between leaves and heterotrophic tissues remains low. Large part of the isotope analysis is concerned with angiosperms, but not spore-bearing tracheophytes. In this study, we explored the 12 C and 13 C isotope distribution in above-ground and below-ground organs of an archaic lycophyte Spinulum annotinum (L.) A.Haines (interrupted clubmoss). The main objectives of this study were to determine the natural distribution of stable carbon isotopes in sporophytes of S. annotinum and to discuss possible causes for differences in δ 13 C. The study revealed that there are significant differences between δ 13 C in different S. annotinum organs. The δ 13 C values varied by about 2.4‰. The highest δ 13 C values were −30.0‰ in roots and the lowest were −32.4‰ in plagiotropic shoot leaves. The distance to a body of water had no significant effect on δ 13 C values in S. annotinum . Outgrowth size did not have a clear relationship with δ 13 C in S. annotinum . The Shannon Diversity Index was a significant predictor for δ 13 C values in S. annotinum . The uncovered δ 13 C and the relationship with abiotic habitat conditions and neighbouring plant species in the community provide a base for future lycophyte ecophysiology research.

Initial growth of clonal seedlings of Passiflora mucronata genotypes in response to paclobutrazol concentrations

Paclobutrazol (PBZ) is a plant growth regulator of the triazole group that can block the biosynthesis of gibberellic acid, resulting in reduced plant height and increased stem diameter. This study aimed to evaluate the effect of different paclobutrazol concentrations on seedling quality of Passiflora mucronata Lam. Two Passiflora mucronata genotypes were used, one resistant (G5) and one tolerant (G7) to fusariosis, prepared as cuttings treated with PBZ. The experimental design was completely randomized, in a 2 x 4 factorial arrangement corresponding to two genotypes (G5 and G7) and four PBZ concentrations (0, 5, 10, and 15 mg plant-1), with three replications of four plants. Data were subjected to analysis of variance, regression analysis, and the F-test, followed by Pearson’s correlation test between variables. PBZ promoted an increase in the plagiotropic shoot diameter and the leaf area index of genotypes G5 and G7, in addition to increased shoot length in genotype G5 and increased number of leaves in genotype G7. PBZ also resulted in increased photosynthesis and stomatal conductance. There was a positive correlation for genotype G5, between the plagiotropic shoot diameter and the leaf transpiration rate, and for genotype G7, between the plagiotropic shoot diameter and the number of leaves. Genotypes G5 and G7 showed different phenotypic responses when subjected to PBZ doses, highlighting the intraspecific divergence of the species.

Morpho-anatomical and physiological differences between sun and shade leaves in Abies albaMill. (Pinaceae, Coniferales): a combined approach.

Morphology, anatomy and physiology of sun and shade leaves of Abies alba were investigated and major differences were identified, such as sun leaves being larger, containing a hypodermis and palisade parenchyma as well as possessing more stomata, while shade leaves exhibit a distinct leaf dimorphism. The large size of sun leaves and their arrangement crowded on the upper side of a plagiotropic shoot leads to self-shading which is explainable as protection from high solar radiation and to reduce the transpiration via the lamina. Sun leaves furthermore contain a higher xanthophyll cycle pigment amount and Non-Photochemical Quenching (NPQ) capacity, a lower amount of chlorophyll b and a total lower chlorophyll amount per leaf, as well as an increased electron transport rate and an increased photosynthesis light saturation intensity. However, sun leaves switch on their NPQ capacity at rather low light intensities, as exemplified by several parameters newly measured for conifers. Our holistic approach extends previous findings about sun and shade leaves in conifers and demonstrates that both leaf types of A. alba show structural and physiological remarkable similarities to their respective counterparts in angiosperms, but also possess unique characteristics allowing them to cope efficiently with their environmental constraints.

Production of coffee fruits (Coffea arabica L.) in different positons and orientation of plagiotropic shoots

This paper aimed at to evaluate the fruit production in different positions of coffee plagiotropic shoot ( Coffea arabica L.), during eight months. Measurements started in October 21 taking five different regions of eight shoots located in the central region of a plant belonging to the cultivar of Rubi MG 1192; located at the Coffee Section from the Federal University of Lavras. The experimental design used was random blocks disposed in factorial scheme, 2x 4x 8, composed by two positions(upper third and lower third), four orientations (east sunrise, west sunset, north and south) and eight evaluations time (from October 2005 to May 2006), totalizing 64 treatments, containing 10 replicates and one plant per plot. There was a reduction in fruit number per shoot during the development and this fact was more proeminent in shoots located in the inferior part of the plant and in period from December to January. The orientations North, South, East and West did not influence the number of fruits during the development.

On the unusual flowering of plagiotropic shoots in the seagrass Posidonia oceanica

The seagrass Posidonia oceanica (L.) Delile can produce plagiotropic (horizontally oriented) and orthotropic (vertically oriented) axes. These axes differ in various morphological and growth characteristics and ecological functions. Only orthotropic shoots are likely to support flowering and seed production. To asses whether flowering may occur on plagiotropic shoots, we examined plagiotropic axes that grew at the edge of a meadow during the flowering of 2003. We identified and analysed 10 rhizome fragments that bore at least one reproductive plagiotropic shoot. We then investigated whether reproductive plagiotropic shoots differed from orthotropic ones in morphological characteristics and investment in flowering (i.e., number of hermaphroditic flowers per inflorescence). Multivariate analysis did not show any significant difference between plagiotropic and orthotropic shoots with regard to the characteristics examined and investment in flowering. Further studies are necessary to ascertain if the observed pattern of flowering is a common or an exceptional event in P. oceanica.

Growth pattern of Carex arenaria (Cyperaceae)

The origin of the orthotropic aerial shoot from the plagiotropic, horizontal rhizome of Carex arenaria L. (Cyperaceae) was studied. A previously proposed adnation or fusion of the first internode of the orthotropic shoot and the fourth internode of the plagiotropic shoot could not be anatomically confirmed. The rhizome branches sympodially and the point of branching results from intercalary meristematic activity in the plagiotropic shoot.

Seedling development and patch formation of the seagrass Posidonia australis in a southeast Australian estuary

Seedlings of the seagrass Posidonia australis are rarely found and little is known about their development. St. Georges Basin, an estuary in southeast Australia, harbours relatively large numbers of P. australis seedlings and patches. Seedlings of varying age were collected from four sites within the estuary. Mature plagiotropic shoots (horizontal rhizomes) on existing beds were tagged to measure vegetative growth and provide a plastochrone interval with which to age the seedlings. The abundance of P. australis seedlings ranged from 0.001 to 0.014 seedlings m −2. Based on the plastochrone intervals (plagiotropic: 33±0.8 days; orthotropic: 48.0±1.4 days) estimated seedling age ranged from 0.7 to 8.2 years. Both the numbers of shoots and leaf areas were related to seedling age, with increases particularly evident between 2 and 5 years. Of 57 seedlings either collected or observed in situ, only 6 had produced a plagiotropic shoot. Rhizome growth for the seedlings ranged from 5.1±0.5 to 17.1±1.3 cm per year, which was slower than the mean rhizome growth of mature plants (21.4±1.0 cm per year). A development time-line was constructed for P. australis for the first 5 years of seedling growth based on the data collected. On average, production of a second shoot occurred at the age of 2.7±0.3 years, and thereafter approximately one shoot was produced per year. Plagiotropic shoots (horizontal rhizomes) did not begin to develop until 4.3±0.7 years.

Revision and description of two new species of Charliea Mamay from Pennsylvanian strata in New Mexico and Utah, USA

Originally, Charliea Mamay was considered to be a pinnately compound leaf having linear–oblong ultimate segments with apices divided into two to four, nearly equal truncated lobes when it was described from the Upper Pennsylvanian of New Mexico. However, evaluation of the type material and newly collected specimens of the generitype as well as other fossils representing two new species demonstrates that the ultimate segments are alternately arranged in two rows (two-ranked) on a narrow stem and that the fossil is not a pinnately compound leaf, but a leafy plagiotropic shoot. Moreover, the apical lobes of the ultimate segments are rounded to pointed and not truncated as first thought. The new species, C. guntheri and C. readii, are distinguished from the generitype, C. manzanitana Mamay, in the shape and size of the ultimate segments (here termed leaves), and the smaller number of veins entering the apical lobes. Charliea guntheri and C. readii occur in the Lower Pennsylvanian of Utah and the Upper Pennsylvanian of New Mexico, respectively, and extend the stratigraphic range of the genus significantly. As a consequence, Charliea seems to exhibit what may be referred to as a modified ‘Lazarus effect’ since the species assigned to it occur at the base and top of the Pennsylvanian but not in the intervening interval.

Thorn and hook ontogeny in Artabotrys hexapetalus (Annonaceae)

Artabotrys hexapetalus is widely planted in the tropics and is known as "climbing ylang-ylang," an ornamental liana or woody climber. New natural sprouts, or water shoots, and those induced by the damage of Hurricane Andrew (24 August 1992) were collected and fixed in formalin/acidic acid/alcohol. Seeds from these plants were planted and grown in a greenhouse where seedling morphology was observed and young material collected and fixed. The development of lateral plagiotropic and orthotropic shoots was studied using both epi-illumination light microscopy and scanning electron microscopy. A series of buds develops in the axils of leaves on the orthotropic shoot. At the lateral margins of the axillary shelf, plagiotropic shoots form that will develop into either vegetative shoots, or thorns, or sympodial shoots that bear hooks and flowers. In between the two marginal buds, a series of median vertical buds develop that either remain dormant or grow out as renewal orthotropic shoots. Previous work that suggested that the plagiotropic shoot buds were displaced out of the median vertical series of supernumerary buds is not supported. The sympodial development of plagiotropic branches as inflorescence hooks is documented.

Photomorphogenesis of white clover (Trifolium repens L.) phytochrome mediated effects on 14C-assimilate partitioning

White clover has a plagiotropic shoot system : it is a typical 'shade avoider' species. In this environment, white clover often experiences competition for light and nutrients from neighbouring plants. This paper reports a study in controlled environments on the effect of light quality on assimilate partitioning between source and sinks and the consequences on plant morphogenesis.The results demonstrated that the source-sink relationships were modified ; far-red plants partitioned more 14C-assimilates to petioles and leaves than did control plants, at the expense of stolons and roots. These modifications in the transport of 14C-labelled assimilates were evident less than 4 days after the commencement of the light treatments.Adding far-red at the end of each photosynthetic period modified plant morphogenesis ; far-red radiation decreased stolon branching and promoted the extension of petioles and internodes. Thus, the strategy of white clover in response to far-red is to redirect its development through a modification of its source-sink relationships in order to allow young leaves to be kept out of the shade. The shoot-root ratio was increased by far-red radiation ; thus phytochrome may act indirectly on nitrogen fixation and nutrient uptake by reducing carbohydrate allocation to the roots.

Light and Electron Microscopic Observations on the Early Ontogeny of the Adventitious Root in Glechoma hederacea L.

Summary In vegetative material of Glechoma hederacea a minimum of two pairs of adventitious roots per node normally occurs on the plagiotropic shoot. At the oldest node of the terminal bud the first initiated pair of primordia is already apparent and the second pair is freqently present. At older nodes additional roots may develop and precocious branching of the root often occurs due to necrosis of the apex. This may already become evident whilst the root is still enclosed within the parent stem. In the orthotropic flowering shoots adventitious roots are normally absent. The provascular tissue of the stem is composed of four strands of procambium separated by tracts of residual meristem and the root is initiated endogenously from the latter tissue and the adjacent layer of cortical parenchyma cells which both undergo de-differentiation to the primary meristematic condition. The root primordium then enlarges and becomes organised into cap, ground meristem and provascular tissue, whilst the apical initials soon show conspicuous vacuolation, suggesting the development of a quiescent centre. No cytological evidence has been obtained to support the theory that breakdown of the stem cortex by the advancing root tip is effected by enzymatic secretion from this organ and it is probable that penetration occurs by mechanical pressure.