Xylem and Phloem in Petioles Are Coordinated With Leaf Gas Exchange in Oaks With Contrasting Anatomical Strategies Depending on Leaf Habit.

As the single link between leaves and the rest of the plant, petioles must develop conductive tissues according to the water influx and sugar outflow of the leaf lamina. A scaling relationship between leaf area and anatomical traits of xylem and phloem is expected to improve the efficiency of these tissues. However, the different constraints compromising the functionality of both tissues (e.

Foliar Pectins and Physiology of Diploid and Autotetraploid Mango Genotypes under Water Stress.

The cultivation of mango in Mediterranean-type climates is challenged by the depletion of freshwater. Polyploids are alternative genotypes with potential greater water use efficiency, but field evaluations of the anatomy and physiology of conspecific adult polyploid trees under water stress remain poorly explored. We combined field anatomical evaluations with measurements of leaf water potential (Ψ) and stomatal conductance (G) comparing one diploid and one autotetraploid tree per treatment with and without irrigation during dry summers (when fruits develop).

How dense can you be? New automatic measures of vein density in angiosperm leaves.

Premise: Because of the trade-off between water loss and carbon dioxide assimilation, the conductivity of the transpiration path in a leaf is an important limit on photosynthesis. Closely packed veins correspond to short paths and high assimilation rates while widely spaced veins are associated with higher resistance to flow and lower maximum photosynthetic rates. Vein length per area (VLA) has become the standard metric for comparing leaves with different vein densities; its measurement typically utilizes digital image processing with varying amounts of human input.

Concluding Embryogenesis After Diaspora: Seed Germination in Illicium Parviflorum.

Albuminous seeds, dispersed with a minimally developed embryo surrounded by nutrient storage tissue, are pervasive across extinct and extant early diverging angiosperm lineages. Typically, seed ontogenic studies have focused on the time between fertilization and seed release, but in albuminous seeds, embryogenesis is incomplete at the time of seed dispersal. Here, I studied the morphological and nutritional relationships between the embryo and the endosperm after seed dispersal in Illicium parviflorum (Austrobaileyales).

Hydraulic tradeoffs underlie enhanced performance of polyploid trees under soil water deficit.

The relationships between aerial organ morpho-anatomy of woody polyploid plants with their functional hydraulics under water stress remain largely understudied. We evaluated growth-associated traits, aerial organ xylem anatomy, and physiological parameters of diploid, triploid, and tetraploid genotypes of atemoyas (Annona cherimola × Annona squamosa), which belong to the woody perennial genus Annona (Annonaceae), testing their performance under long-term soil water reduction. The contrasting phenotypes of vigorous triploids and dwarf tetraploids consistently showed stomatal size-density tradeoff.

Sieve tube structural variation in Austrobaileya scandens and its significance for lianescence.

Lianas combine large leaf areas with slender stems, features that require an efficient vascular system. The only extant member of the Austrobaileyaceae is an endemic twining liana of the tropical Australian forests with well-known xylem hydraulics, but the vascular phloem continuum aboveground remains understudied. Microscopy analysis across leaf vein orders and stems of Austrobaileya scandens revealed a low foliar xylem:phloem ratio, with isodiametric vascular elements along the midrib, but tapered across vein orders.

Changes in ploidy affect vascular allometry and hydraulic function in Mangifera indica trees.

The enucleated vascular elements of the xylem and the phloem offer an excellent system to test the effect of ploidy on plant function because variation in vascular geometry has a direct influence on transport efficiency. However, evaluations of conduit sizes in polyploid plants have remained elusive, most remarkably in woody species. We used a combination of molecular, physiological and microscopy techniques to model the hydraulic resistance between source and sinks in tetraploid and diploid mango trees.

Conductivity of the phloem in mango (Mangifera indica L.).

Mango (Mangifera indica L., Anacardiaceae), the fifth most consumed fruit worldwide, is one of the most important fruit crops in tropical regions, but its vascular anatomy is quite unexplored. Previous studies examined the xylem structure in the stems of mango, but the anatomy of the phloem has remained elusive, leaving the long-distance transport of photoassimilates understudied.

Idioblasts and peltate hairs as distribution networks for water absorbed by xerophilous leaves.

Capparis odoratissima is a tree species native to semi-arid environments of South America where low soil water availability coexists with frequent night-time fog. A previous study showed that water applied to leaf surfaces enhanced leaf hydration, photosynthesis and growth, but the mechanisms of foliar water uptake are unknown. Here, we combine detailed anatomical evaluations with water and dye uptake experiments in the laboratory, and use immunolocalization of pectin and arabinogalactan protein epitopes to characterize water uptake pathways in leaves.

Arabinogalactan proteins mediate intercellular crosstalk in the ovule of apple flowers.

AGP-rich glycoproteins mediate pollen-ovule interactions and cell patterning in the embryo sac of apple before and after fertilization. Glycoproteins are significant players in the dialog that takes place between growing pollen tubes and the stigma and style in the angiosperms. Yet, information is scarce on their possible involvement in the ovule, a sporophytic organ that hosts the female gametophyte.

Scaling of phloem hydraulic resistance in stems and leaves of the understory angiosperm shrub Illicium parviflorum.

Premise Of The Study: Recent studies in canopy-dominant trees revealed axial scaling of phloem structure. However, whether this pattern is found in woody plants of the understory, the environment of most angiosperms from the ANA grade (Amborellales-Nymphaeales-Austrobaileyales), is unknown.

Methods: We used seedlings and adult plants of the understory tropical shrub Illicium parviflorum, a member of the lineage Austrobaileyales, to explore the anatomy and physiology of the phloem in their aerial parts, including changes through ontogeny.

Not all 'pine cones' flex: functional trade-offs and the evolution of seed release mechanisms.

Seed dispersal is critical for plants, but the evolution of mechanisms that actually release seeds from their parents is not well understood. We use the reproductive cones of conifers, specifically the Pinaceae clade, to explore the factors driving the evolution of different release mechanisms in plants. We combine comparative anatomical and phylogenetic analyses to test whether fundamental trade-offs in the mechanical and hydraulic properties of vasculature underlie the evolution of two seed release mechanisms: cone scale flexion and cone scale shedding.

Why are the seed cones of conifers so diverse at pollination?

Background And Aims: Form and function relationships in plant reproductive structures have long fascinated biologists. Although the intricate associations between specific pollinators and reproductive morphology have been widely explored among animal-pollinated plants, the evolutionary processes underlying the diverse morphologies of wind-pollinated plants remain less well understood. Here we study how this diversity may have arisen by focusing on two conifer species in the pine family that have divergent reproductive cone morphologies at pollination.

Phloem networks in leaves.

The survival of all vascular plants depends on phloem and xylem, which comprise a hydraulically coupled tissue system that transports photosynthates, water, and a variety of other molecules and ions. Although xylem hydraulics has been extensively studied, until recently, comparatively little is known quantitatively about the phloem hydraulic network and how it is functionally coupled to the xylem network, particularly in photosynthetic leaves. Here, we summarize recent advances in quantifying phloem hydraulics in fully expanded mature leaves with different vascular architectures and show that (1) the size of phloem conducting cells across phylogenetically different taxa scales isometrically with respect to xylem conducting cell size, (2) cell transport areas and lengths increase along phloem transport pathways in a manner that can be used to model Münch's pressure-flow hypothesis, and (3) report observations that invalidate da Vinci's and Murray's hydraulic models as plausible constructs for understanding photosynthate transport in the leaf lamina.

Pollen-pistil interaction in pawpaw (), the northernmost species of the mainly tropical family Annonaceae.

Premise Of The Study: The pawpaw, , is an underutilized fruit crop native to North America that belongs to the mainly tropical, early-divergent family Annonaceae. is the only genus within the Annonaceae with species adapted to cold climates. A thorough analysis of its reproductive biology, specifically pollen-pistil interaction during the progamic phase, is essential to understand both its adaptation to cold climates and how to optimize its fertilization and fruit set.

Maintenance of carbohydrate transport in tall trees.

Trees present a critical challenge to long-distance transport because as a tree grows in height and the transport pathway increases in length, the hydraulic resistance of the vascular tissue should increase. This has led many to question whether trees can rely on a passive transport mechanism to move carbohydrates from their leaves to their roots. Although species that actively load sugars into their phloem, such as vines and herbs, can increase the driving force for transport as they elongate, it is possible that many trees cannot generate high turgor pressures because they do not use transporters to load sugar into the phloem.

Prolonged embryogenesis in Austrobaileya scandens (Austrobaileyaceae): its ecological and evolutionary significance.

The embryology of basal angiosperm lineages (Amborella, Nymphaeales and Austrobaileyales) is central to reconstructing the early evolution of flowering plants. Previous studies have shown that mature seeds in Austrobaileyales are albuminous, with a small embryo surrounded by a substantial diploid endosperm. However, little is known of seed ontogeny and seedling germination in Austrobaileya scandens, sister to all other extant Austrobaileyales.

Pollen tube access to the ovule is mediated by glycoprotein secretion on the obturator of apple (Malus × domestica, Borkh).

Background And Aims: Within the ovary, the obturator bridges the pathway of the pollen tube from the style to the ovule. Despite its widespread presence among flowering plants, its function has only been studied in a handful of species, and the molecules involved in pollen tube-obturator cross-talk have not been explored hitherto. This work evaluates the involvement of glucans and glycoproteins on pollen tube growth in the obturator of apple flowers ( Malus × domestica) .

Floral biology and ovule and seed ontogeny of Nymphaea thermarum, a water lily at the brink of extinction with potential as a model system for basal angiosperms.

Background And Aims: Nymphaea thermarum is a member of the Nymphaeales, of one of the most ancient lineages of flowering plants. This species was only recently described and then declared extinct in the wild, so little is known about its reproductive biology. In general, the complete ontogeny of ovules and seeds is not well documented among species of Nymphaea and has never been studied in the subgenus Brachyceras, the clade to which N.

Arabinogalactan proteins mark stigmatic receptivity in the protogynous flowers of Magnolia virginiana (Magnoliaceae).

Premise Of The Study: Factors affecting floral receptivity in angiosperms remain opaque, but recent studies suggest that the acquisition of stigmatic receptivity associated with cell-wall-related arabinogalactan proteins (AGPs) may be a widespread feature of flowering plants. Here, the time during which a stigma is receptive is evaluated and related to the secretion of AGPs in Magnolia virginiana, a protogynous member of an early-divergent angiosperm clade (magnoliids) with a clearly discernible female receptive phase.

Methods: Magnolia virginiana flower phenology was documented, and histochemical changes in the stigma before and after pollination were examined.

Glycoprotein composition along the pistil of Malus x domestica and the modulation of pollen tube growth.

Background: The characteristics of pollen tube growth are not constant, but display distinct patterns of growth within the different tissues of the pistil. In the stigma, the growth rate is slow and autotrophic, whereas in the style, it is rapid and heterotrophic. Very little is known about the interactions between these distinct maternal tissues and the traversing pollen tube and the role of this interaction on the observed metabolism.

Arabinogalactan-protein secretion is associated with the acquisition of stigmatic receptivity in the apple flower.

Background And Aims: Stigmatic receptivity plays a clear role in pollination dynamics; however, little is known about the factors that confer to a stigma the competence to be receptive for the germination of pollen grains. In this work, a developmental approach is used to evaluate the acquisition of stigmatic receptivity and its relationship with a possible change in arabinogalactan-proteins (AGPs).

Methods: Flowers of the domestic apple, Malus × domestica, were assessed for their capacity to support pollen germination at different developmental stages.