Direct Evidence for a Radial Gradient in Age of the Apple Fruit Cuticle

The pattern of cuticle deposition plays an important role in managing strain buildup in fruit cuticles. Cuticular strain is the primary trigger for numerous fruit-surface disorders in many fruit crop species. Recent evidence indicates a strain gradient may exist within the apple fruit cuticle. The outer layers of the cuticle are more strained and thus more susceptible to microcracking than the inner layers. A radial gradient in cuticle age is the most likely explanation. Our study aimed to establish whether (or not) deposition of new cutin in a developing apple fruit occurs on the inner surface of the cuticle, i.e., immediately abutting the outward-facing epidermal cell wall. Developing apples were fed with 13C oleic acid through the skin. Following a 14-d period for incorporation, the fruit was harvested and the cuticular membranes (CMs) isolated enzymatically. The CMs were then ablated to varying extents from the inner or the outer surfaces, using a cold atmospheric pressure plasma (CAPP). Afterwards, the ablated CMs were dewaxed and the 13C contents were determined by mass spectrometry. The incorporation of 13C in the cutin fraction was higher than in the wax fraction. The 13C content was highest in non-ablated, dewaxed CM (DCM) and decreased as ablation depth from the inner surface increased. There was no change in 13C content when ablation was carried out from the outer surface. As fruit development proceeded, more 13C label was found towards the middle of the DCM. These results offered direct evidence for deposition of cutin being on the inner surface of the cuticle, resulting in a radial gradient in cuticular age—the most recent deposition (youngest) being on the inner cuticle surface (abutting the epidermal cell wall) and the earliest deposition (oldest) being on the outer surface (abutting the atmosphere).

Cellulose intrafibrillar mineralization of biological silica in a rice plant

The essence of morphological design has been a fascinating scientific problem with regard to understanding biological mineralization. Particularly shaped amorphous silicas (plant opals) play an important role in the vital activity in rice plants. Although various organic matters are associated with silica accumulation, their detailed functions in the shape-controlled mineralization process have not been sufficiently clarified. In the present study, cellulose nanofibers (CNFs) were found to be essential as a scaffold for silica accumulation in rice husks and leaf blades. Prior to silicification, CNFs ~ 10 nm wide are sparsely stacked in a space between the epidermal cell wall and the cuticle layer. Silica nanoparticles 20–50 nm in diameter are then deposited in the framework of the CNFs. The shape-controlled plant opals are formed through the intrafibrillar mineralization of silica nanoparticles on the CNF scaffold.

Asymmetric water transport in dense leaf cuticles and cuticle-inspired compositionally graded membranes

Most of the aerial organs of vascular plants are covered by a protective layer known as the cuticle, the main purpose of which is to limit transpirational water loss. Cuticles consist of an amphiphilic polyester matrix, polar polysaccharides that extend from the underlying epidermal cell wall and become less prominent towards the exterior, and hydrophobic waxes that dominate the surface. Here we report that the polarity gradient caused by this architecture renders the transport of water through astomatous olive and ivy leaf cuticles directional and that the permeation is regulated by the hydration level of the cutin-rich outer cuticular layer. We further report artificial nanocomposite membranes that are inspired by the cuticles’ compositionally graded architecture and consist of hydrophilic cellulose nanocrystals and a hydrophobic polymer. The structure and composition of these cuticle-inspired membranes can easily be varied and this enables a systematic investigation of the water transport mechanism.

Stem integrity inArabidopsis thalianarequires a load-bearing epidermis

ABSTRACTBecause plant cells are glued to each other via their cell walls, failure to coordinate growth among adjacent cells can create cracks in tissues. Here, we find that the unbalanced growth of inner and outer tissues in theclavata3 de-etiolated3(clv3 det3) mutant ofArabidopsis thalianastretched epidermal cells, ultimately generating cracks in stems. Stem growth slowed before cracks appeared alongclv3 det3stems, whereas inner pith cells became drastically distorted and accelerated their growth, yielding to stress, after the appearance of cracks. This is consistent with a key role of the epidermis in restricting growth. Mechanical property measurements recorded using an atomic force microscope revealed that epidermal cell wall stiffness decreased indet3andclv3 det3epidermises. Thus, we hypothesized that stem integrity depends on the epidermal resistance to mechanical stress. To formally test this hypothesis, we used theDET3gene as part of a tissue-specific strategy to complement cell expansion defects. Epidermis-driven DET3 expression restored growth and restored the frequency of stem cracking to 20% of theclv3 det3mutant, demonstrating the DET3-dependent load-bearing role of the epidermis.

Cellulose Intrafibrillar Mineralization of Biological Silica in a Rice Plant

The essence of morphological design has been a fascinating scientific problem with regard to understanding biological mineralization. Particularly shaped amorphous silicas (plant opals) play an important role in the vital activity in rice plants. Although various organic matters are associated with silica accumulation, their detailed functions in the shape-controlled mineralization process have not been sufficiently clarified. In the present study, cellulose nanofibers (CNFs) were found to be essential as a scaffold for silica accumulation in rice husks and leaf blades. Prior to silicification, CNFs ~10 nm wide are sparsely stacked in a space between the epidermal cell wall and the cuticle layer. Silica nanoparticles 20–50 nm in diameter are then deposited in the framework of the CNFs. The shape-controlled plant opals are formed through the interfibrillar mineralization of silica nanoparticles on the CNF scaffold.

Comparative leaf and wood anatomical characteristics of Chrysophyllum (Sapotaceae) relate to taxonomy of the species in Thailand

Prasawang S, Srinual A. 2020. Comparative leaf and wood anatomical characteristics of Chrysophyllum (Sapotaceae) relate to taxonomy of the species in Thailand. Biodiversitas 21: 1578-1587. Anatomical attributes are important tools for taxonomic studies of plants. The present study compared anatomical characteristics (i.e. lamina, petiole and wood) of two species of Chrysophyllum (namely Chrysophyllum cainito L. and C. roxburghii G.Don) belonging to family Sapotaceae in Thailand to develop taxonomic identification keys for two species of Chrysophyllum. Peeling and clearing methods were used for epidermal study, paraffin method for lamina and petiole transverse sections and standard microtome sectioning for anatomical analyses of wood. The findings of this study demonstrated the leaf and wood anatomical features presenting in C. cainito differs from those in the species of C. roxburghii including 1) shape and outline of epidermal cell wall 2) presence or absence of T-shaped trichome 3) presence or absence of inclusions 4) shape of vascular bundle and accessory bundle in midrib 5) shape of petiole and vascular bundle 6) grouping type of vessel 7) type of axial parenchyma 8) presence or absence of inclusions in rays and 9) thickness of fiber walls. Therefore, these characteristics can be used valuably as additional data in case of taxonomic studies of Thai Chrysophyllum.

Fruit Morphology as Taxonomic Features in Five Varieties of Capsicum annuum L. Solanaceae

Variations in the fruit morphological features of Capsicum annuum varieties were studied. Varieties studied include var. abbreviatum, var. annuum, var. accuminatum, var. grossum, and var. glabriusculum. The fruit morphology revealed attenuated fruit shape with rounded surfaces in var. glabriusculum, and cordate fruit shape with flexuous surface in var. annuum, abbreviatum and accuminatum. The fruit is a berry and may be green, yellow, or red when ripe. The fruit epidermal cell-wall patterns are polygonal in shape with straight and curved anticlinal walls in all the five varieties. The fruit of var. abbreviatum and var. grossum is trilocular, while that of var. accuminatum and annuum is bilocular, and that of var. glabriusculum is tetralocular. Capsicum annuum var. glabriusculum had the highest mean number of seeds (108.4) and var. annuum had the lowest number of seeds (41.3) per fruit. The fruit is conspicuously hollowed in var. glabriusculum, accuminatum, and annuum but inconspicuously hollowed in var. abbreviatum and var. grossum. These features are shown to be good taxonomic characters for delimiting the five varieties of Capsicum annuum.

Seed-coat anatomy and microsculpturing of the genus Erysimum (Brassicaceae) in Northeast of Iran

In order to examine the systematic application of seed-coat characters in Erysimum (Brassicaceae) distributed in Northeast of Iran (Khorassan provinces), the seeds of nine species (14 populations) were examined using the light microscope (LM) and the scanning electron microscope (SEM). According to results of the LM, diagnostic characters at the specific level are seed shape, wing width, epidermal cell-wall shape, and seed-surface sculpture. The SEM investigation at high magnifications reveals that seven types of seed-surface sculpture pattern are distinguishable, including 1) reticulate, the basic type; 2) ocellate; 3) papillate; 4) reticulate-papillate; 5) scalariform; 6) ribbed; and 7) reticulate-ocellate. The seed coat typically consists of four layers, including the epidermis layer, the subepidermis layer, the sclerotic (or palisade) layer, and the parenchymatous layer. Some of the layers may be absent in some species. Finally, an identification key to the investigated taxa is provided based on the seed-coat characters used in this research.