Kidney-shaped Guard Cells Research Articles

Histological description of Saxifraga paniculata leaves with special focus on structures that release CaCO3

Saxifraga paniculata is a subalpine succulent perennial plant arranged in a rosette that is usually found in shallow soil among limestone rocks. Stereoscopic, light and scanning electron microscopy were used to describe the anatomical structure of S. paniculata leaves, paying special attention to structures related to CaCO3 (calcium carbonate) release. Anomocytic stomata are unevenly distributed on each leaf face, being absent in the lower third. The basal leaf margin presents translucent pluricellular trichomes of variable length and width. Towards the apical margin, trichomes become teeth. Both trichomes and teeth are completely covered with whitish CaCO3 crystals. Each tooth has a circular cavity connected to a single hydathode through pores. Clearing treatment revealed camptodromous leaf venation. Anatomical structure shows a bifacial cross-section with spongy mesophyll cells at basal part, becoming heterogeneous at the apex with palisade mesophyll on the adaxial face. Hydathodes are epithematic and connected to outer cavities via two kidney-shaped guard cells showing large substomatal cavity. The epithem is surrounded by a thickened sheath and is formed of highly packed elongated cells with interspersed tracheary elements. CaCO3 deposits consist of microscopic crystals with varying geometries, of which the rhombus is the basic unit.

Flanking Support: How Subsidiary Cells Contribute to Stomatal Form and Function.

Few evolutionary adaptations in plants were so critical as the stomatal complex. This structure allows transpiration and efficient gas exchange with the atmosphere. Plants have evolved numerous distinct stomatal architectures to facilitate gas exchange, while balancing water loss and protection from pathogens that can egress via the stomatal pore. Some plants have simple stomata composed of two kidney-shaped guard cells; however, the stomatal apparatus of many plants includes subsidiary cells. Guard cells and subsidiary cells may originate from a single cell lineage, or subsidiary cells may be recruited from cells adjacent to the guard mother cell. The number and morphology of subsidiary cells varies dramatically, and subsidiary cell function is also varied. Subsidiary cells may support guard cell function by offering a mechanical advantage that facilitates guard cell movements, and/or by acting as a reservoir for water and ions. In other cases, subsidiary cells introduce or enhance certain morphologies (such as sunken stomata) that affect gas exchange. Here we review the diversity of stomatal morphology with an emphasis on multi-cellular stomata that include subsidiary cells. We will discuss how subsidiary cells arise and the divisions that produce them; and provide examples of anatomical, mechanical and biochemical consequences of subsidiary cells on stomatal function.

Speedy Grass Stomata: Emerging Molecular and Evolutionary Features

Stomata in most land plants are formed by a pair of guard cells, controlling the water loss and the carbon dioxide uptake. The development, patterning, and density of stomata are fundamental traits for stomatal function, contributing to plant growth and productivity (Pillitteri and Torii, 2012). The stomata of most plant species consist of two kidney-shaped guard cells, while stomata of grass species are formed by two dumbbell-shaped guard cells flanked by two subsidiary cells (Figure 1A). The four-celled stomatal complex in grasses may facilitate a fast response to environmental cues for efficient photosynthesis and water use, possibly through the rapid transport of ions and osmolytes between guard cells and subsidiary cells (see Jezek and Blatt, 2017; Chen et al., 2017 and references therein).

Anatomy and Morphological Study of Mentigi Gunung (Vaccinium varingiaefolium (Blume) Miq.) in Area of Mount Batok-Indonesia

<p>Mentigi Gunung (<em>Vaccinium varingiaefolium</em> (Blume) Miq.), endemic plant of Java which dominates sub-alpine area of Mount Batok. This study aimed to characterize plant’s anatomical and morphological structure for conservation purpose. Microscopic and macroscopic approaches used for organs observation. Morphological observation showed that this plant has a tap root, circular stem with lenticels on its surface. It has red young stem with a lot of trichomes, brown old stem, oval leaves with integer margins. Leaves have stone cells, cuticles, idioblasts. Young leaves are red and turn green. Flowers are purple with five sepals, five petals, 10 androecium and one syncarp gynoecium. Trichomes spread all over flower structures. The type of microspore is tetraeder. The gynoecium sits on the receptacle composed of five carpellum with inpherus ovulus. The fruits are green, globular, with trichomes and turn black when ripe. It has stone cells with purple cytoplasm and golden brown seeds. Vascular bundle is opened collateral type; the type is parasitic with kidney-shaped guard cells.</p><div><p class="Els-keywords"><strong>Keywords:</strong> Anatomy; morphology; mentigi gunung; <em>Vaccinium varingiaefolium</em> (Blume) Miq.</p></div>

식물에서 기공 형태에 대한 오해와 진실

The walls of guard cells have many different specialized features. Guard cells are present in leaves of bryophytes, ferns and almost all of the vascular plants. Guard cells show considerable morphological diversities. It is understood that the stomata show two types in terms of morphological characterizations of guard cells. The first type is only found in a few monocots including Poaceae and Cyperaceae. In rice and corn, guard cells have the morphological characteristics of dumbbell shape. The morphological characteristics of dumbbell shape always have subsidiary cells. The other type is found in every dicots and many monocots and they are kidney-shaped guard cells. The plants of kidney-shaped guard cells rarely have subsidiary cells except Commelina communis L. Therefore, it could be concluded that two types of the morphological characteristics of guard cells cannot divide according to monocots or dicots. Every plants in which stomatal characteristic features were all different, most of them belong to kidney-shaped guard cells. However in case of Sedum sarmentosum, guard cells were shown to be long and narrow lips type. In Tradescantia virginiana, the shape of guard cells could be called perfectly to half-moon type. Therefore, it could be concluded that kidney-shaped types are all different in some way, but dumbbell-shaped types are almost constant.

Oryza sativa H+-ATPase (OSA) is Involved in the Regulation of Dumbbell-Shaped Guard Cells of Rice.

The stomatal apparatus consists of a pair of guard cells and regulates gas exchange between the leaf and atmosphere. In guard cells, blue light (BL) activates H+-ATPase in the plasma membrane through the phosphorylation of its penultimate threonine, mediating stomatal opening. Although this regulation is thought to be widely adopted among kidney-shaped guard cells in dicots, the molecular basis underlying that of dumbbell-shaped guard cells in monocots remains unclear. Here, we show that H+-ATPases are involved in the regulation of dumbbell-shaped guard cells. Stomatal opening of rice was promoted by the H+-ATPase activator fusicoccin and by BL, and the latter was suppressed by the H+-ATPase inhibitor vanadate. Using H+-ATPase antibodies, we showed the presence of phosphoregulation of the penultimate threonine in Oryza sativa H+-ATPases (OSAs) and localization of OSAs in the plasma membrane of guard cells. Interestingly, we identified one H+-ATPase isoform, OSA7, that is preferentially expressed among the OSA genes in guard cells, and found that loss of function of OSA7 resulted in partial insensitivity to BL. We conclude that H+-ATPase is involved in BL-induced stomatal opening of dumbbell-shaped guard cells in monocotyledon species.

Microculture effects on leaf epidermis and root structure in Sclerocarya birrea subsp. caffra

Micropropagation of woody plants is beset by a number of challenges such as cell and tissue abnormality, which ultimately affect survival of plantlets ex vitro. The aim of the study was to evaluate the effects of in vitro microenvironments, in particular photoperiod, on the structure of the leaf epidermis and adventitious roots under photomixotrophic conditions. Control plants were grown under photoautotrophic conditions in a growth chamber. Stomatal density (number of stomata per mm 2) on the abaxial leaf surfaces was highest for the control (221.9 ± 13.99) and the 16-h photoperiod treatment (206.6 ± 15.28). Stomata of plants grown under a 16-h photoperiod had fully expanded kidney-shaped guard cells that closely resembled stomata in the control plants. Formation of epicuticular wax was least for in vitro plants grown under a 24-h photoperiod. One of the main structural differences was the relative thickness of the inner and outer periclinal cell walls of the root epidermis between the control plants and in vitro plantlets. Control plants developed a thicker epidermis compared to that of in vitro plantlets. The root endodermis in the control plants was also comparatively thicker and more regular than that of in vitro plantlets. Control plants had a greater proportion of vascular tissue relative to the total area of the root cross-section compared to in vitro plants due to the development of xylem and phloem tissues. A micropropagation system that facilitates the modification of the in vitro microclimate may reduce the structural abnormalities of conventional microcultures.

Ultrastructure of stomatal development in Arabidopsis (Brassicaceae) leaves

Stomatal development was studied in wild-type Arabidopsis leaves using light and electron microscopy. Development involves three successive types of stomatal precursor cells: meristemoid mother cells, meristemoids, and guard mother cells (GMCs). The first two types divide asymmetrically, whereas GMCs divide symmetrically. Analysis of cell wall patterns indicates that meristemoids can divide asymmetrically a variable number of times. Before meristemoid division, the nucleus and a preprophase band of microtubules become located on one side of the cell, and the vacuole on the other. Meristemoids are often triangular in shape and have evenly thickened walls. GMCs can be detected by their roughly oval shape, increased starch accumulation, and wall thickenings on opposite ends of the cells. Because these features are also found in developing stomata, stomatal differentiation begins in GMCs. The wall thickenings mark the division site in the GMC since they overlie a preprophase band of microtubules and occur where the cell plate fuses with the parent cell wall. Stomatal differentiation in Arabidopsis resembles that of other genera with kidney-shaped guard cells. This identification of stages in stomatal development in wild-type Arabidopsis provides a foundation for the analysis of relevant genes and of mutants defective in stomatal patterning, cell specification, and differentiation.

Organisation of microtubules and actin filaments in the cortex of differentiating Selaginella guard cells

Using fluorescent probes and confocal laser scanning microscopy we have examined the organisation of the microtubule and actin components of the cytoskeleton in kidney-shaped guard cells of six species of Selaginella. The stomata of Selaginella exhibit novel cytoskeletal arrangements, and at different developmental stages, display similarities in microtubule organisation to the two major types of stomata: grass (dumbbell-shaped) and non-grass (kidney-shaped). Initially, cortical microtubules and F-actin radiate from the stomatal pore and extend across the external and internal periclinal cell surfaces of the guard cells. As the stomata differentiate, the cytoskeleton reorients only along the internal periclinal walls. Reorganisation is synchronous in guard cells of the same stoma. Microtubules on the inner periclinal walls of the guard cells now emanate from areas of the ventral wall on either side of the pore and form concentric circles around the pore. The rearrangement of F-actin is similar to that of microtubules although F-actin is less well organised. Radial arrays of both microtubules and F-actin are maintained adjacent to the external surfaces. Subsequently, in two of the six species of Selaginella examined, microtubules on both the internal and external walls become oriented longitudinally and exhibit no association with the ventral wall. In the other four species, microtubules adjacent to the internal walls revert to the initial radial alignment. These findings may have implications in the development and evolution of the stomatal complex.

A scanning electron microscope study of normal and vitrified leaves from Datura insignis plantlets cultured in vitro

The surface anatomy of normal and vitreous leaves of plantlets obtained from Datura insignis Barb Rodr nodal segment cultures was compared using scanning electron microscopy. Normal and vitrified leaves are similar in several ways. They are both amphistomatic, and have similar distributions of glandular and non-glandular trichomes. Stomata have similar length, diameter and distribution in normal and vitreous plants. Immature stomata, which have closed pores, and plugged stomata, which contain an amorphous material between their guard cells, occur in both normal and vitrified leaves. Normal and vitreous leaves differ in the frequency of normal and abnormal stomata. Normal stomata have kidney-shaped guard cells and resemble closely those found in field-grown plants, whereas abnormal stomata have deformed guard cells. Normal stomata represent approximately 80% of the total number of stomata in normal leaves, but only 7% of the total number of stomata in vitreous leaves. Abnormal stomata represent 90% of the total number in vitreous leaves. The deformation of guard cells could possibly be a mechanical impediment to stomatal function.