Stomata begin to close within 24 h of imposing soil flooding. We investigated whether the stomatal response was triggered by reduced photosynthetic efficiency in young, fully expanded leaves of flooded plants. Chlorophyll fluorescence measurements indicated that ФpsII the effective quantum yield of PS II,decreased after stomata began to close in flooded plants. Changes in qP mirrored those of ФpsII, ФpsII was not affected by daytime patterns of stomatal conductance in well-drained plants but was reduced by stomatal closure in flooded plants. Fv/Fm a measure of the overall photosynthetic efficiency of dark- adapted plants, decreased after 57 h of flooding. Therefore, prolonged soil flooding adversely affected the thylakoid membranes. QN, a measure of the amount of captured energy dissipated as heat and therefore, unused by the photosynthetic machinery, began to increase after 32 h of flooding and continued to rise thereafter. The interdependence of the changes in chlorophyll fluorescence parameters and the flooding-induced closure of stomata is discussed.
The epicuticular wax covering on plant surface plays important roles in protecting plants against UV radiation. However, the role of epicuticular wax in affecting leaf gas exchange under enhanced ultraviolet-B (UV-B) radiation remains obscure. In the present study, different aged leaves of Brassica napus were used to analyze the responses of crystal structure and chemical constituents of epicuticular wax to UV-B radiation and the effects of such responses on gas exchange indices. Enhanced UV-B radiation significantly decreased the amount of esters in all leaves except the first leaf, amount of secondary alcohols in the second, third and fourth leaves, and amount of primary alcohols in the second and third leaves, while increased the amounts of ketones and aldehydes in the first leaf. Enhanced UV-B level had no significant effect on the amounts of alkanes and total wax in all leaves. Exposure to UV-B radiation resulted in wax fusion on adaxial leaf and stomata opening on abaxial leaf. Fusions of plates and rods on adaxial leaf surface covered most of the stomata, thereby influencing the photosynthesis in the upper mesophyll of leaves. Enhanced UV-B level significantly reduced the net photosynthesis rate (PN) but increased the stomata conductance (gₛ), concentrations of intercellular CO₂ (Cᵢ), and transpiration rate (E) in all leaves. Both UV-B radiation and the wax fusion induced by enhanced UV-B radiation resulted in different stomata status on abaxial and adaxial leaf surface, causing decrease of PN, and increase of gₛ, Cᵢ and E in leaves.
The present study on lemon balm (Melissa officinalis L.) covered flowering biology, monitoring of pollinating insects and floral nectary structure. The micromorphology of epidermal cells of the nectary was investigated using scanning electron microscopy. The nectariferous tissues were observed using light microscopy based on semi-thin sections. Lemon balm flowered from the second decade of June until September. Buds opened from early morning hours until noon. Flowers lived for 24 hours, on the average. Their primary pollinator was the honey bee. The beginning of nectar secretion was found to be at the bud swell stage. The automorphic nectary forms a disc with four protrusions at the base of the nectary. Three smaller ones and one larger than the other ones were distinguished among them. No stomata were found on the lower protuberances, whereas on the highest part anomocytic stomata were present, the number of which was 15. The stomata exhibited different development stages and they were situated above other epidermal cells. In their outline, they were ellipsoidally shaped (18 x 23 μm) and they had average-sized cuticular ledges. They produced a smooth cuticle and wax granules. In cross section, the nectary tissues were composed of a singlelayered epidermis and 9 – 11 layers of the nectary parenchyma. Their thickness was 198 μm. In longitudinal section, the height of the nectary was within a range of 354 – 404 μm. The epidermal cells produced thin outer cell walls. Some of them were completely filled with strongly stained cytoplasm, whereas others showed a high degree of vacuolisation. But the nectary parenchyma cells were marked by poorly stained cytoplasm, a large nucleus and vacuolisation of varying degree.
The biology of flowering and the micromorphology of Cornus alba flowers were studied using light and scanning electron microscopy. The flowering of white dogwood in 2008 lasted 35 days, and the lifespan of a single flower was 3 days. The number of flowers per inflorescence was variable (on the average, it was 89). The largest group of insects visiting the flowers of C. alba comprised Hymenoptera (mainly bees and andrenids), then ants, dipterans and beetles. They foraged the dogwood flowers most intensively between 11.00 and 15.00. The inconspicuous four-petalled flowers of C. alba were characterised by the occurrence of T-shaped, two-armed non-glandular trichomes covering the receptacle as well as observed on the petals of the corolla, the style of the pistil and the anthers in a smaller number. The trichomes were covered by a thick cuticle with characteristic outgrowths. They contained a living protoplast, and plastids were observed in the cytoplasm of the trichome cells. In addition, anomocytic stomata were found in the epidermis of the receptacle and in the epidermis of the corolla petals. The stigma of the pistil and the adaxial epidermis of the petals were composed of very numerous conical papillae.
We used via light and scanning electron microscopy to study the leaf epidermis of five Solidago taxa from southwestern Poland. Light microscopy was employed to describe the epidermal surface, including stomatal types, the shape of epidermal cell walls, stomatal density, the distribution of stomata between the abaxial and adaxial epidermis, and stomatal guard cell length. From these observations we calculated the stomatal index (SI) and stomatal ratio (SR) as the basis for defining the type of leaf. From LM of transverse sections of leaf we described mesophyll structure, the presence of secretory canals, adaxial and abaxial epidermis thickness, and leaf thickness. We examined cuticular ornamentation, trichome features and epicuticular secretions by SEM. As determined by discriminatory analysis, the most important traits distinguishing these taxa were the stomatal index of the adaxial epidermis, leaf thickness, features of the walls of epidermal cells, and the presence and features of trichomes. On the basis of observations and measurements we created a key for distinguishing Solidago taxa.
In Poland Scorzonera hispanica L. is rare in the wild. This species is used as a vegetable and medicinal plant. Currently, attempts are being made to introduce this plant into cultivation in Poland. In this study, comparative analyses were conducted of the epidermis surface micromorphology and anatomical structure of the leaves of S. hispanica 'Maxima' and 'Meres'. The investigations were performed using fluorescence, light and scanning electron microscopy. The cuticle on the surface of epidermal cells is smooth or striated. In the epidermis, there are anomocytic stomata. The stomatal index in the epidermis of the studied cultivars is 9.3-11%. In the midrib of the leaf, there is an aerial cavity which occupies a substantial area. In this place, cracking and breaking of the leaf blade were observed. Over the aerial cavity under the adaxial epidermis, there is a single layer of collenchyma cells and 1-2 rows of parenchyma cells. Tangential collenchyma is also present between the abaxial epidermis and large vascular bundles located in the midrib and on both sides of the large vascular bundles in the lamina. This tissue strengthens the leaf margin. The mesophyll cells located in the abaxial epidermis of the midrib form protrusions surrounding the large vascular bundles. The leaves of S. hispanica represent the equifacial type.
The main question in this review is of whether and how the cytoskeleton of guard cells is involved in stomata movements. The main function of stomata is the regulation of the rate of gas exchange between the plant environment and underlying plant tissues. As a result of special morphology and anatomy GCs form the stomatal pore. It can open or close in a controlled manner via internal or external signal-induced changes in GCs turgor pressure, volume and shape. The mechanism of stomata movement is a complex process. A network of actin microfilaments and microtubules, dynamic polymers collectively known as the cytoskeleton forms protein fibril systems in GCs. CT elements are dynamic structures, interconnected to different cell structures. The organization of CT during morphogenesis of stomata is very important in establishing the size and shape of GCs. It is well documented that AFs and MTs are involved in stomata movements and can modify the ability of GCs to respond to environmental and hormonal stimuli. Data gathered clearly suggest that the organization of CT elements is not a direct effect of stomata movements. Several investigation procedures for study of the CT role in stomata functioning, including GCs treatment with anti-CT drugs (disrupters or stabilizers), have been analyzed and discussed in this review but the question of what role AFs and MTs play in stomata movements and how they work still remains open. The availability of new CT visualization techniques and the usage of mutants to study this problem is a good perspective for further research.
Floral nectaries of Inula helenium L. only occurred in disc florets and were situated above the inferior ovary. The shape of the investigated glands (five-armed star with rounded tips and deep incisions - observed from above) clearly differed from the shape of the nectaries of other Asteraceae, also the height of nectary was much lower (129 µm). The glandular tissue of the nectaries of elecampane was composed of a single-layered epidermis and 5--9 layers of secretory cells. Nectar was released through modified stomata, mainly arranged in the top part of the gland. The secretory cells were characterised by granular cytoplasm and the presence of a large, often lobate, cell nucleus. In the cytosol, numerous amoeboid plastids, mitochondria, Golgi bodies and ribosomes were present. In small vacuoles, myelin-like structures, fibrous material and vesicles with the content of substances which can be secretion, were observed. The plastid stroma showed different electron density and the presence of internal tubules and plastoglobules. Vesicular extensions forming bright zones were visible between the membranes of the nuclear envelope. Adjacent to the plasmalemma, as well as between the plasmalemma and the cell wall, secretory vesicles occurred, indicating the granulocrine mechanism of nectar secretion.
The study involved screening and SEM analysis of the micromorphological features of the abaxial leaf surface of ordinary epidermal cells, stomata and trichomes of two varieties of Quercus cerris L. The results indicated features distinguishing the two varieties: in var. austriaca the wax is present as crystalloids in the form of simple platelets, while in var. cerris the wax appears as a smooth layer. Moreover, the results point to some special characteristics of Q. cerris in relation to other Quercus species. The approximately square, not ellipsoid, shape of the peristomatal rims is typical of the species Q. cerris L.
Condition of epistomatal wax on the abaxial surface of the current and previous-year needles of damaged silver fir trees (Abies alba Mill.), both from the polluted Risnjak and "clean" Donja Dobra sites in Gorski Kotar region, both influenced by pollutants coming from Europe, during two years, three times a year, were examined with Scanning Electron Microscope. In the course of time the wax tubules on the epistomatal rims of stomata in polluted, but also in "clean" needles surface, become fused and agglomerated rapidly to various extents of morphologically different types of amorphous wax crusts, primarily compact and particulate ones. This process begins very early, especially in polluted Risnjak site, and may be interpreted as a possible result of air pollution. However, the recrystalization, or production of new tubules, also appears relatively quickly in mostly cases. Quantitative estimations indicate a very large total amount of amorphous wax crusts in the current-year needles, and a very high percentage of the same wax in previous-year needles. Amorphous wax crusts cover stomatal pores, as well as the rims, disturbing the normal gas exchange. Statistically there is a signicant tendency of increase in wax degradation in the needles of the polluted site in comparison with those of the unpolluted one, but there is an insignificant wax degradation among the needles of damaged trees within each site. These results confirmed most of the research done in our preliminary report.
The conducted study related to the structure of the floral nectaries of Rhododendron japonicum (A. Gray) J. V. Suringar ex E. H. Wilson. The structure of the secretory epidermis of the nectaries was analysed by using scanning electron microscopy (SEM). Rhododendron japonicum develops the superior pistil with a 5-loculed ovary equipped in five ribs. The nectary gland is located in the lower part of the ovary. In the nectary regions located on the extension of the ribs of the ovary, stomata were very numerous. In the upper part of the nectary, stomata were arranged individually or in small clusters, whereas at its half-height they formed stomatal areas. The stomata were at different growth stages. They were arranged in different directions. The stomata developed on the nectary surface according to the mosaic pattern. The stomata from the lower situated part of the nectary had a different structure than those occurring in the upper half of the nectary. The stomata in the nectaries of Rh. japonicum belong to the actinocytic type. The cuticle layer in the upper part of the nectary was better developed and had a characteristic sculpture, whereas in the lower part it was smooth.
Stomatal cell length was examined in four closely related taxa of sect. Phleum in the genus Phleum (P. nodosum, P. pratense and in two cytotypes of P. commutatum). It was found that the polyploid taxa (P. pratense, 2n = 6x = 42 and P. commutatum, 2n = 4x = 28) have longer stomatal cells than their diploid relatives (P. nodosum, 2n = 2x = 14 and P. commutatum, 2n = 2x = 14). In these two pairs of taxa, stomatal cell length can be a rapid and useful indirect ploidy level indicator and can assist in their identification. Material taken from live and dried specimens of a given taxon did not differ in stomatal cell length, meaning that different cytotypes can be identified from herbarium material as well.
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.