Stomata in Bouea, Mangifera and Spondias (Anacardiaceae)

Comparative Leaves Anatomical Studies of Bouea, Mangifera and Spondias (Anacardiaceae) in Malaysia

Ghazalli M. N., Mohammad A. L. (2014)

Mohd Norfaizal Ghazalli , Abdul Latiff Mohammad,

In Journal of Life Sciences 8(9) – doi:10.17265/1934-7391/2014.09.005 –

https://scinapse.io/papers/295402088

AbstractLeaves anatomy of two species of Bouea, 11species of Mangifera and two species of Spondias were studied in order to see the differences in stomata type, petiole, midrib and lamina anatomy and leaf venation. This study aims to use anatomical characters for species and genus identification. Common characters observed were the absence of trichomes, closed vascular bundles, uniseriate epidermal layers, resin canal in parenchyma cells, anticline wall patterns and druses crystals in leaf lamina transverse sections. All species displayed closed vascular bundles except Mangifera pajang which showed a combination of medullary vascular bundles. Uniseriate epidermal layer was observed in all species. All the species showed straight-wavy anticlinal walls. Druses crystals were found in the parenchyma cells of all the species. Four types of stomata were observed namely anomocytic, anisocytic, staurocytic and diacytic. Anomocytic, anisocytic and staurocytic stomata were observed in Mangifera, diacytic in Bouea and anomocytic in Spondias.

Ultrastructural observations of anthers, staminodes, and pollen grains of mango

Scanning electron micrograph of mature anthers: 1. Abaxial side of a pre-dehiscent anther. Scale bar: 100 µm. 2. Irregular-shaped groove and stomata (arrows) on the surface of the anther. Scale bar: 20 µm. 3. Development of longitudinal slit (ls) (arrows) on the anther. Scale bar: 100 µm. 4. Side view of a dehisced anther (arrows) with residual pollen grains (po). Scale bar: 100 µm.

Ultrastructural observations of anthers, staminodes, and pollen grains of mango (Mangifera indica L. var. Beneshan; Anacardiaceae)

Muniraja M., Vijayakakshmi G., Naik M. L., Terry Rg., Khan P. S. S. V. (2019)

M. Muniraja, G. Vijayalakshmi, M. Lakshmipathi Naik, Rg. Terry, P. S. Sha Valli Khan,

In Palynology https://doi.org/10.1080/01916122.2019.1633437 –

https://www.tandfonline.com/doi/full/10.1080/01916122.2019.1633437?scroll=top&needAccess=true

Scanning electron micrograph of staminodes of Mangifera indica L.: 1. Capitate staminode with a filament from a male flower (arrows). Scale bar: 30 µm. 2. Staminode with a terminal hook (arrow). Scale bar: 30 µm. 3. A staminode with irregular cells on the surface and parallel ornamentation (arrows). Scale bar: 10 µm. 4. Stomata (sm) (arrows) on the surface of the staminode. Scale bar: 20 µm. 5. The presence of stomata (arrows) and the secretion (sc) (arrow) of nectar from the stomata (arrows). Scale bar: 10 µm. 6. Expanded view of nectar drops (nb) (arrows). Scale bar: 10 µm.

Abstract

The ultrastructure of anthers, staminodes, and pollen of Mangifera indica L. was studied using scanning electron microscopy (SEM), and pollen viability assessed using light (LM) and fluorescence microscopy (FM). Ultrastructural observation revealed anther surfaces with polygonal cells and hollow centres arranged in a reticulate manner, with swollen cells on the edges of the anther surfaces. Anther dehiscence is longitudinal, with pollen released through a long slit in both thecae. The average length and width of staminodes of male and hermaphroditic flowers measured 0.7 mm × 0.35 mm and 0.65 mm × 0.3 mm, respectively. Distinct ridge and hook-like outgrowths on the adaxial surface of staminodes are described, as are staminode surfaces comprised of long, irregular cells with stomata exuding nectar. Staminodes produced no pollen. Anthers of male flowers produced more pollen grains (536–537) than did anthers of hermaphrodite flowers (510–511). Pollen grains are tricolporate, have reticulate perforate exine ornamentation, and are bi-cellular at dispersal. Anther and staminode size and pollen production was greater but not significantly different in male versus hermaphrodite flowers. In contrast, the fluorochromatic reaction (FCR) test and FM observations found significantly higher pollen viabilities in hermaphroditic (50.1%) versus male (40.4%) flowers. This research provides new ultrastructural characters potentially useful in future taxonomic studies of mango and other Anacardiaceae. Results presented here may also be useful in pollination studies, and in the improvement of mango breeding programmes and commercial fruit production.

The inactive stomata of Anabasis

ULTRASTRUCTURE AND DEVELOPMENT OF THE INACTIVE STOMATA OF ANABASIS ARTICULATA (FORSK.) MOQ

Gedalovich E., Fahn A., (1983)

In Am J Bot. 70(1): 88-96 – doi:10.1002/j.1537-2197.1983.tb12436.x –

https://pubmed.ncbi.nlm.nih.gov/30139053/

Abstract

The guard cells of Anabasis articulata mature and senesce a short distance from the intercalary meristem in which they form. When the guard cells reach final size, their ultrastructure is similar to that of stomata of other plants. At this stage, they contain clearly definable, numerous mitochondrial profiles, chloroplasts with starch grains and plastoglobuli, active Golgi bodies, a large nucleus that stains deeply for chromatin and large vacuoles. During later stages of development the whole protoplasmic content becomes very dense, with myelin-like figures and crystals appearing in the vacuoles. The cell walls thicken considerably. This is especially true of the tangential walls, where the microfibrils of different lamellae vary in their orientation. It is suggested that as a result of these ultrastructural changes the guard cells lose the ability to move.

Nectar of stomata-free nectaries crossing the cuticle

Figure 2 Cuticular canals in pericarpal nectaries of Spathodea campanulata (Bignoniaceae), seen using a scanning electron microscope; samples were prepared as described in figure 1. In A, a transverse section showing detail of the secretory epithelium; the arrow indicates a channel through the cuticle. In B, frontal view of the secretory face showing the cuticle with the opening of the cuticular canals (arrows). 

How does the nectar of stomata-free nectaries cross the cuticle?

Paiva E. A. S. (2017)

Elder Antônio Sousa Paiva¹ 

¹Departamento de Botânica, Instituto de Ciências Biológicas, Universidade Federal de Minas Gerais, 31270-901, P.O. Box 486, Belo Horizonte, MG, Brazil. 

In Acta Bot. Bras. 31(3) –  Belo Horizonte July/Sept. 2017 – https://doi.org/10.1590/0102-33062016abb0444 –

https://www.scielo.br/scielo.php?script=sci_arttext&pid=S0102-33062017000300525

ABSTRACT

In many glandular structures, departure from the cell is only one step in the process of exudate release to the plant surface. Here the set of events that lead nectar to the external environment is presented and discussed mainly for stomata-free nectaries. After being synthesized, the nectar or some of its component needs to be released to the environment where it performs its functions. Nectar precursors derived from cell metabolism need to cross several barriers, such as the cell membrane and cell wall, in order to become nectar. Then the nectar must cross the cuticle or pass through stomata in order to be offered to plant mutualists. Release through stomata is a simple mechanism, but the ways by which nectar crosses the cuticle is still controversial. Hydrophilic pathways in the cuticle and repetitive cycles of rupture or cuticle detachment are the main routes for nectar release in stomata-free nectaries. In addition to nectar, there are other exogenous secretions that must leave the protoplast and reach the plant surface to perform their function. The ways by which nectar is released discussed herein are likely relevant to understanding the release of other hydrophilic products of the secretory process of plants.

Growth-mediated sensing of long-term cold in plants (stomatal development)

Figure 1 | How plants sense prolonged cold temperatures. Many plant species will not flower in the spring unless they have experienced a long period of cold weather. Zhao et al.¹ reveal a mechanism that enables Arabidopsis thaliana plants to track their passage through winter. The authors report that the protein NTL8 has a key role in this process. If plants are grown in warm conditions, the concentration of NTL8 in individual cells remains low because of rapid growth and frequent cell divisions. Such plants make the protein FLC, which blocks flowering^2,3. However, the slow growth and infrequent cell divisions that occur in the cold enable NTL8 to accumulate slowly in cells. The authors report that NTL8 drives the expression of the protein VIN3. VIN3 represses⁵ the production of FLC, enabling plants to flower when they subsequently experience warm temperatures.

Growth-mediated sensing of long-term cold in plants (some proteins that regulate stomatal development)

Iida H., Mähönen A. P. (2020)

Hiroyuki Iida, Ari Pekka Mähönen,

In Nature 583: 690-691 – doi: 10.1038/d41586-020-02060-7 –

https://www.nature.com/articles/d41586-020-02060-7

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PDF version

Plants of the same species, growing at a particular location, typically all flower at the same time. This synchronous flowering is important for maximizing the probability of successful reproduction through pollination. The response of plants to cold exposure provides them with a way to align their flowering in spring. Because daily temperatures fluctuate, long-term rather than short-term cold is the key signal required for a flowering cue; prolonged cold followed by warmer weather provides an indication that winter has ended, bringing the advent of spring and flowering time. Plants therefore need to track how long they have experienced the cold conditions of winter. Writing in Nature, Zhao et al.¹ reveal how long-term cold is integrated as quantitative information in plants.

Long-term exposure to cold promotes accelerated flowering of many plants after the cold period. This cold-mediated process, called vernalization, has been studied for many decades, and some of the key underlying molecular mechanisms have been discovered. In the model plant Arabidopsis thaliana, the gene FLOWERING LOCUS C (FLC) encodes a repressor protein (Fig. 1) that functions as a central ‘off switch’ to block flowering^2,3. However, FLC expression becomes downregulated as a result of prolonged cold exposure, and this downregulated state is maintained when warm weather arrives^3,4, thus promoting flowering. The gene VERNALIZATION INSENSITIVE3 (VIN3) encodes a protein that represses FLC, and it therefore acts as an activator for flowering⁵. The expression of VIN3 increases gradually in the cold^5,6, a characteristic that could be useful as a way of sensing prolonged cold weather. However, it was unclear how exposure to the cold resulted in a slow increase in VIN3 expression.

Figure 1 | How plants sense prolonged cold temperatures. Many plant species will not flower in the spring unless they have experienced a long period of cold weather. Zhao et al.¹ reveal a mechanism that enables Arabidopsis thaliana plants to track their passage through winter. The authors report that the protein NTL8 has a key role in this process. If plants are grown in warm conditions, the concentration of NTL8 in individual cells remains low because of rapid growth and frequent cell divisions. Such plants make the protein FLC, which blocks flowering^2,3. However, the slow growth and infrequent cell divisions that occur in the cold enable NTL8 to accumulate slowly in cells. The authors report that NTL8 drives the expression of the protein VIN3. VIN3 represses⁵ the production of FLC, enabling plants to flower when they subsequently experience warm temperatures.

The process of cellular expansion also might promote asymmetry between cells through a dilution mechanism. In the asymmetric division of cells that occurs during the development of plant ‘pore’ structures called stomata, some proteins that regulate stomatal development show localization that is polarized to one side of the cell before division. Those polarized proteins in the membrane of the cell recruit other signalling components and promote cellular asymmetry. One of the regulators involved promotes cell growth, and it has therefore been hypothesized that polarized growth generates asymmetry by diluting key factors and signalling molecules. Taken together, these examples suggest that the growth rate itself is a key determinant of developmental and physiological responses. It will be exciting to see whether other growth-mediated regulatory mechanisms will be discovered in the future.

Amazon set to dry as trees narrow stomata

Randerson J., Ralph J., Cicerone C. M., (2018)

https://physicsworld.com/a/amazon-set-to-dry-as-trees-narrow-stomata/

As carbon dioxide concentrations rise, the Amazon rainforest is likely to become drier whilst woodlands in Africa and Indonesia become wetter. That’s at least partly due to the direct response of vegetation to higher levels of the gas, according to a new study.

“People tend to think that most of the disruption will come from heat going into the oceans, which, in turn, will alter wind patterns,” said James Randerson of the University of California, Irvine, US. “We have found that large-scale changes in rainfall can, in part, be attributed to the way tropical forests respond to the overabundance of carbon dioxide humans are emitting into the atmosphere, particularly over dense forests in the Amazon and across Asia.”

Small pores known as stomata on the underside of tree leaves open to take in carbon dioxide for photosynthesis and emit water vapour in a process known as transpiration. If there’s more carbon dioxide in the atmosphere, the stomata open less widely, reducing the amount of water evaporated into the air. When multiplied across the rainforest, this process can affect winds and the flow of moisture from the ocean.

“In many tropical forest regions, the moisture supplied by transpiration, which connects water underground at the root level directly to the atmosphere as it is pulled up to the leaves, can contribute as much as moisture evaporated from the ocean that rains back down at a given location – which is normal rainforest recycling,” said Gabriel Kooperman, who’s now at the University of Georgia, US.

With higher carbon dioxide concentrations, however, forests evaporate less moisture into the air and fewer clouds are likely to form above the Amazon. “Rather than [joining with the usually abundant clouds and] raining over the forest, water vapour from the Atlantic Ocean blows across the South American continent to the Andes mountain range, where it comes down as rain on the mountain slopes, with limited benefit to the rainforest in the Amazon basin,” Kooperman said.

The forests in Central Africa and the Maritime Continent, an area between the Pacific and Indian oceans that includes Malaysia, Papua New Guinea and the Indonesian archipelago, are predicted increased rainfall, on the other hand.

On islands such as Borneo, Java and Sumatra, which are surrounded by humid air above warm ocean surfaces, the reduction in evaporation is projected to lead to warming over the forests.

“You’ll get a stronger contrast in heating over the islands compared to the nearby ocean, and so it will enhance a natural ocean-land breeze, pulling in more moisture from these neighbouring ocean systems to increase rainfall over the forests,” said Randerson.

The team’s results, published in Nature Climate Change, indicate that the response of tropical vegetation to higher carbon dioxide can be an important driver of climate change in the tropics.

According to Kooperman, the resulting droughts and forest mortality in the Amazon and a potential increase in flooding in other rainforests may have an impact on biodiversity, freshwater availability and food supplies for economically vulnerable populations.

Scientists find precise control of terminal division during plant stomatal development

A conserved but plant specific CDK-mediated regulation of DNA replication protein A2 in the precise control of stomatal terminal division

The model for RPA2 function in stomatal terminal division regulation and DNA repair progression Credit: IBCAS

Yang K., Le J. (2019)

Kezhen Yang, Jie Le,

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In PNAS – See : Scientists find precise control of terminal division during plant stomatal development –

https://phys.org/news/2019-08-scientists-precise-terminal-division-stomatal.html

Stomata are plant-specific epidermal structures that consist of paired guard cells surrounding a pore. The opening and closing of these micro-valves facilitate carbon dioxide uptake for photosynthesis and reduce excessive water loss in plants.

Recently, a research group led by Prof. Le Jie at the Institute of Botany of the Chinese Academy of Sciences (IBCAS) found a genetic suppressor of flp stomatal defects. They found that RPA2a, a core subunit of Replication Protein A (RPA) complexes, acted downstream from the core cell cycle genes of CDKB1 to ensure terminal division during stomatal development and the formation of paired guard cells to create functional stomata units.

RPA is a heterotrimeric single-stranded DNA (ssDNA)-binding protein complex that is required for multiple aspects of DNA metabolism, including DNA replication, recombination, and repair. The homologues of each of the three RPA subunits (RPA1-3) are well conserved in eukaryotes, including humans.

Le’s group demonstrated that CDK-mediated phosphorylation at the N-terminus of RPA2a was essential for RPA functioning and localization. The scientists also showed that Serine-11 and Serine-21 are evolutionarily conserved CDK-phosphorylation sites. Furthermore, their results revealed that being phosphorylated by CDK was required for RPA2a to respond to DNA damage.

The study, entitled “A conserved but plant specific CDK-mediated regulation of DNA replication protein A2 in the precise control of stomatal terminal division,” was published online in PNAS on August 20, 2019. Yang Kezhen is the first author and Le Jie is the corresponding author.

The modulation of stomatal conductance and photosynthetic parameters

The modulation of stomatal conductance and photosynthetic parameters is involved in Fusarium head blight resistance in wheat

Francesconi S., Balestra G. M. (2020)

Sara Francesconi, Giorgio Mariano Balestra,

In PLOS One 15(6): e0235482 – https://doi.org/10.1371/journal.pone.0235482 –

https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0235482

Abstract

Fusarium head blight (FHB) is one of the most devastating fungal diseases affecting grain crops and Fusarium graminearum is the most aggressive causal species. Several evidences shown that stomatal closure is involved in the first line of defence against plant pathogens. However, there is very little evidence to show that photosynthetic parameters change in inoculated plants. The aim of the present study was to study the role of stomatal regulation in wheat after F. graminearum inoculation and explore its possible involvement in FHB resistance. RT-qPCR revealed that genes involved in stomatal regulation are induced in the resistant Sumai3 cultivar but not in the susceptible Rebelde cultivar. Seven genes involved in the positive regulation of stomatal closure were up-regulated in Sumai3, but it is most likely, that two genes, TaBG and TaCYP450, involved in the negative regulation of stomatal closure, were strongly induced, suggesting that FHB response is linked to cross-talk between the genes promoting and inhibiting stomatal closure. Increasing temperature of spikes in the wheat genotypes and a decrease in photosynthetic efficiency in Rebelde but not in Sumai3, were observed, confirming the hypothesis that photosynthetic parameters are related to FHB resistance.

The responses of stomata to ABA and temperature are interrelated

The responses of stomata to abscisic acid and temperature are interrelated

Honour S. J., Webb A. A. R., Mansfield T. A. (1995)

Sarah J. Honour, Alex A. R. Webb , Terence Arthur Mansfield,

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In Proc. Royal Soc B – https://doi.org/10.1098/rspb.1995.0044 –

https://royalsocietypublishing.org/doi/10.1098/rspb.1995.0044

Abstract

The usual response of stomata to abscisic acid (ABA) is a promotion of closure or an inhibition of opening. There are, however, a few reports that at low temperatures the stomata of chill-sensitive species show a reversal of this normal effect, i.e. ABA causes stomatal opening. We have reinvestigated the interactions between ABA and temperature on stomatal movements in detached epidermis of two species which are not chill sensitive, Bellis perennis and Cardamine pratensis, and, for comparison, the subtropical plant Commelina communis. A major effect of low temperatures was to reduce the stomatal response to ABA. This applied to all species (i. e. whether chill sensitive or not), suggesting that it is a widespread occurrence which may be of physiological and ecological significance. It was also demonstrated that, above approximately 15 °C, the magnitude of the stomatal response to ABA tends to increase with temperature and hence temperature-induced stomatal opening is moderated by the presence of ABA. These data suggest that some reinterpretation is required of the role of ABA during periods of water shortage. We propose that an important regulatory role of the hormone is to limit stomatal opening at periods when the evapotranspirational demand is greatest at higher temperatures, but to allow opening when temperatures are low and thereby facilitate the uptake of carbon dioxide.

Blue Light Improves Stomatal Function and Dark-Induced Closure

Blue Light Improves Stomatal Function and Dark-Induced Closure of Rose Leaves (Rosa x hybrida) Developed at High Air Humidity

Terfa M. T., Olsen J. E., Torre S. (2020)

Meseret Tesema Terfa, Jorunn Elisabeth Olsen, Sissel Torre,

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In Frontiers in Plant Science ( IF 4.402 ) – DOI: 10.3389/fpls.2020.01-

https://www.x-mol.com/paper/1288183835631730688

Abstract

Plants developed under constant high (>85%) relative air humidity (RH) have larger stomata that are unable to close completely in response to closing stimuli. Roses (Rosa x hybrida) developed in high RH have previously been shown to have high water loss during leaf dehydration and reduced dark-induced closure resulting in a shorter postharvest life. In this study, the effect of B-light on stomatal function under high RH conditions was investigated. The ability of rose leaves developed under continuous high (90%) or moderate (60%) RH to close their stomata in response to darkness and leaf dehydration assay was studied. Moreover, the level and regulation of ABA in light and darkness in relation to B-light was measured. Our results show that increased B-light proportion improved stomatal function and dark-induced stomatal closure under high RH conditions and that was associated with increased [ABA] in general and a dynamic ABA peak during darkness. Furthermore, increased B-light during the day was associated with the presence of high β-glucosidase activity during night. This indicates that B-light is important as a signal to activate the β-glucosidase enzyme and release ABA during night. Altogether, the improved stomatal function and reduced transpiration in combination with increased [ABA] indicate that preharvest B-light plays an important role in governing stomatal functionality and ABA homeostasis under high RH and can be a useful method to improve postharvest water balance of roses.