Action of growth regulators on the cotyledonary stomata ofCucumis sativus L.: Structure and ontogeny

Anomocytic stomata and stomata with single subsidiary cells are commonly observed Sometimes a stoma appears anisocytic. Double cytoplasmic connections between nearby stomata and division of guard cells with persistent or degenerating nuclei are seen in GA. One or more divisions of guard cells, displaced guard cells and single guard cells with or without pore are noticed in SUC. Formation of single guard cells is a common feature in TIBA. Paracytic stomata, one and a half stomata and persistent stomatal initials are seen in SUL. COUM seems to be not inhibitory inCucumis sativus. In COL stomata with unequal guard cells, unequal stomatal cells with thickening in between but without intervening pore, stoma with double pores, persistent stomatal initials which may be solitary or in groups with varying shapes and with one or two nuclei of different shapes are noticed. The growth regulators affect the frequency of stomata, epidermal cells; stomatal index; size of guard and epidermal cells.     

Structure,Ontogeny and Taxonomic Significance of Stomata in Some Cucurbitaceae

Stomatal structure, ontogeny in vegetative and floral organs of 9 genera and 12 species of Cucurbitaceae are described. The stomatal types conform to aperigenous, monoperigenous, diperigenous, hemipara-mesoperigenous and para-mesoperigenous types of Fryns-Claessens & Van Cotthem (1973). Stomatal abnormalities such as contiguous stomata, single guard cells with or without pore, one and a half stomata, degeneration of one or both the guard cells, cytoplasmic connections between guard cells of neighbouring stomata and a guard cell of a stoma and an adjacent epidermal cell, and division of guard cells are described. Stomata index, frequency of stomata, epidermal cells, size of guard and epidermal cells and organwise distribution of stomata are given. Stomatal studies does not support the view that the Cucurbitaceae are related to the Passifloraceae. The inclusion of 9 genera and 12 species studied in the tribe Cucumerineae is justified.     

Epidermal studies in some Indian cultivars of Bougainvilleas

Epidermal studies in fifteen Indian cultivars of Bougainvilleas are described. The epidermal cells are polygonal isodiametric, or elongated with thick straight arched or slightly sinuous walls. Parallel culticular striations are radiating from guard cells. The mature stomata are anomocytic, paracytic and with a single subsidiary cell. The abnormal types noticed are: single guard cells with or without pores, arrested development, variously oriented contiguous stomata, cytoplasmic connections between nearby stomata and epidermal or subsidiary cells, and persistent stomatal cells. The development of anomocytic stomata is perigenous while that of the other types is mesogenous. Fifteen cultivars of Bougainvilleas are separated on the basis of bract colour, stomatal frequency and index per unit area.     

Variation in the structure and development of foliar stomata in the Euphorbiaceae

The structure and ontogeny of foliar stomata were studied in 50 species of 28 genera belonging to 17 tribes of the family Euphorbiaceae. The epidermal cells are either polygonal, trapezoidal, or variously elongated in different directions and diffusely arranged. The epidermal anticlinal walls are either straight, arched or sinuous. The architecture of cuticular striations varies with species. The mature stomata are paracytic (most common), anisocytic, anomocytic and diacytic. Occasionally a stoma may be tetracytic, cyclocytic or with a single subsidiary cell. The ontogeny of paracytic stomata is mesogenous dolabrate or trilabrate, mesoperigenous dolabrate; that of diacytic stomata is mesogenous dolabrate, whereas that of anisocytic stomata is mesogenous trilabrate; rarely an anisocytic stoma may be mesoperigenous. Hemiparacytic stomata are mesoperigenous unilabrate; tetracytic stomata are mesoperigenous dolabrate and anomocytic stomata perigenous. Abnormalities encountered include four types of contiguous stomata, stomata with a single or both guard cells aborted and persistent stomatal initials. Cytoplasmic connections between the guard cells of two adjacent stomata or the guard cell of a stoma and an adjacent epidermal/subsidiary cell, or both types occurring in a species, were noticed. The stomatal development, distribution, diversity and basic stomatal type with reference to systematics are discussed.     

Abaxial and adaxial stomata from Pima cotton (Gossypium barbadense L.) differ in their pigment content and sensitivity to light quality

Sensitivity to light quality and pigment composition were analysed and compared in abaxial and adaxial stomata of Gossypium barbadense L. (Pima cotton). In most plants, abaxial (lower) stomatal conductances are higher than adaxial (upper) ones, and stomatal opening is more sensitive to blue light than to red. In greenhouse-grown Pima cotton, abaxial stomatal conductances were two to three times higher than adaxial ones. In contrast, adaxial stomatal conductances were 1·5 to two times higher than abaxial ones in leaves from growth chamber-grown plants. To establish whether light quality was a factor in the regulation of the relationship between abaxial and adaxial stomatal conductances, growth-chamber-grown plants were exposed to solar radiation outdoors and to increased red light in the growth chamber. In both cases, the ratios of adaxial to abaxial stomatal conductance reverted to those typical of greenhouse plants. We investigated the hypothesis that adaxial stomata are more sensitive to blue light and abaxial stomata are more sensitive to red light. Measurements of stomatal apertures in mechanically isolated epidermal peels from growth chamber and greenhouse plants showed that adaxial stomata opened more under blue light than under red light, while abaxial stomata had the opposite response. Using HPLC, we quantified the chlorophylls and carotenoids extracted from isolated adaxial and abaxial guard cells. All pigments analysed were more abundant in the adaxial than in the abaxial guard cells. Antheraxanthin and β-carotene contents were 2·3 times higher in adaxial than in abaxial guard cells, comparing with ad/ab ratios of 1·5–1·9 for the other pigments. We conclude that adaxial and abaxial stomata from Pima cotton have a differential sensitivity to light quality and their distinct responses are correlated with different pigment content.     

Humidity Responses of Stomata and the Potassium Content of Guard Cells

Humidity responses of stomata and changes in the potassium contentof their guard cells were investigated in intact plants anddetached epidermal strips of Valerianella locusta (L.) Betcke.Potassium content was determined by Macallum‘s stain.It was found that changes in stomatal aperture caused by decreasingor increasing humidity were followed only after a delay by changesin the potassium content of the guard cells. By comparison,if stomatal movements occurred in response to changes in illuminationthe relative potassium content of the guard cells correlatedcontinuously with the changes in stomatal aperture. Since thepotassium content of the guard cells changed only after mostof the stomatal movements in response to changes in humiditywere completed changes in potassium content and humidity responsesof stomata can be described as following a hysteresis curve.     

Influence of mutagenic factors on the epidermis of tomatillo,currant tomato and tomato

Epidermal features of control, 16 treated and 7 mutants ofPhysalis ixocarpa BROT. (tomatillo),Lycopersicon esculentum MILL. (tomato) andL. pimpinellifolium MILL. (currant tomato) are studied. Although the distribution, ontogenesis and mature structure of stomata in control as well as in treated and mutant plants were similar, the mutagens reduced the stomatal abnormalities which were abundant (60%) inP. ixocarpa. Maximum rectification was found after combined treatment of gamma radiation (5.16 C kg^-1 [= 20 kR]) + 1 % dimethyl sulphate. Methyl ethane sulfonate, gamma radiation and gamma radiation + DMS caused an increase in epidermal cell size irrespective of the leaf size but in DMS and diethyl sulphate treated plants, a close negative correlation between leaf size and epidermal coll size was observed. The size and frequency of stomata were also affected, the large leaf usually showed high frequency and small size stomata. The data reveal that mutagens affect the epidermal structures differently.     

Engineering for drought avoidance: expression of maize NADP-malic enzyme in tobacco results in altered stomatal function

Water is a principal limitation to agricultural production during drought and in arid regions of the world. Mechanisms that plants use to cope with drought can be grouped into two different strategies: drought tolerance and drought avoidance. Previous efforts toward engineering plants for improved performance during drought have focused on drought tolerance, the ability to adjust to dry conditions. This report addresses the engineering of a drought-avoidance phenotype, which allows for the conservation of water during plant growth. The majority of water lost from plants occurs through stomata. When stomata are open, potassium, chloride and/or malate are present at high concentrations in guard cells. The accumulation of large numbers of ions during stomatal opening increases the turgor pressure of the guard cells, which results in increased pore size. Expression of a single gene from maize, NADP-malic enzyme (ME), which converts malate and NADP to pyruvate, NADPH, and CO(2), resulted in altered stomatal behaviour and water relations in tobacco. The ME-transformed plants had decreased stomatal conductance and gained more fresh mass per unit water consumed than did the wild type, but they were similar to the wild type in their growth and rate of development. Providing chloride via the transpiration stream partially reversed the effects of ME expression on stomatal aperture size, which is consistent with the interpretation that expression of ME altered malate metabolism in guard cells. These results suggest a role for malic enzyme in the mechanism of stomatal closure, as well as a potential mechanism for genetically altering plant water use.     

Cadmium-induced plant stress investigated by scanning electrochemical microscopy

In vivo oxygen evolution above single stomata in Brassica juncea has been used to investigate, for the first time, the effect of Cd-induced stress as imaged by scanning electrochemical microscopy (SECM). SECM images showed a clear stomatal structure-a pore, whose aperture is modulated by two guard cells, serving as the conduit for the oxygen produced. Lower stomatal density and larger stoma size were found in plants treated with 0.2 mM CdCl2 compared with control plants. Either the introduction of Cd caused a slower cell replication in the plane of the epidermis, hence fewer stomata, and/or the number of open stomata was reduced when plants were under Cd-stress. Oxygen evolution above individual stomatal complexes in Cd-treated plants was lower than that from control plants, as determined from the electrochemical current above the middle of each stoma. All guard cells under illumination were swollen, indicating that the stomata were open in both control and treated plants. Thus, decreased oxygen evolution in response to Cd cannot be attributed to simple closing of the stomata, but to a lower photosynthetic yield. SECM provides an excellent tool for monitoring the effects of Cd on photosynthetic activity at the scale of individual stomata.     

An analysis of the mechanics of guard cell motion

This paper presents a mechanical analysis of the cellular deformations which occur during the opening and closing of stomata. The aperture of the stomatal pore is shown to be a result of opposing pressures of the guard and adjacent epidermal cells. The analysis indicates that the epidermal cells have a mechanical advantage over the guard cells. With no mechanical advantage, an equal reduction in the turgor pressure of both guard and epidermal cells would have a neglible effect upon stomatal aperture. However, due to the mechanical advantage of the surrounding cells, the stomatal aperture increases with equal reductions in turgor, until the adjacent epidermal cells become flaccid. The minimum diffusion resistance of the pore occurs at this point. Further reductions in guard cell turgor lead to closure of the pore. The analysis further demonstrates how the shape, size, wall thickness and material properties of the guard cell walls influence their behavior.     

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.     

Structure of Polymorphic Stomata in Canella winterena (L.) Geartn. (Canellaceae)

The presence of 10 types of normal stomata along with 4 subtypes, one intermediate type between stephanocytic and hemiparacytic and some abnormal stomatal structures both in the vegetative and floral organs of Canella winterena (L.) Geartn. (Canellaceae) is reported here. The epidermal cells are polygonal, isodiametric in surface view with straight anticlinal walls. The stomata are amphibrachyparacytic, anomocytic, anisocytic, brachyparacytic, brachyparatetracytic, cyclocytic, hemiparacytic, laterocytic, holoparacytic, stephanocytic, one intermediate type between stephanocytic and hemiparacytic, etc. Abnormalities like contiguous stomata, different types of twin stomata and cytoplasmic bridge between adjacent stomata, stomata with single guard cell, single guard cell with pore juxtaposed with normal stoma are also found. The presence of giant stomata is a significant finding. (© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

GFP-mTn融合蛋白对蓝猪耳生活细胞微丝骨架的标记

用农杆菌介导法将嵌合基因GFP-mTn(mTn是微丝结合蛋白Talin的微丝结合域,可以显示活体细胞中微丝的结构)导入蓝猪耳。经激光共聚焦显微镜观察了转基因植株的各种不同组织中融合蛋白的表达和分布情况。在叶片的表皮细胞、保卫细胞、根部的皮层细胞中有融合蛋白的不同程度表达。但仅在保卫细胞中微丝标记状况良好,显示基因表达的组织特异性。经光诱导处于开放态的气孔的保卫细胞微丝呈网状结构,在细胞内无规则分布;经黑暗诱导处于关闭态的气孔保卫细胞中微丝束沿保卫细胞纵轴排列,呈卷曲状分布,并观察到螺旋和环状的微丝结构。在转基因植株的其他部位,例如茎表皮细胞、根毛细胞和花粉粒中,未检测到目的基因的表达。本研究获得的转基因植株为研究气孔运动过程中微丝动态变化提供了有用的材料。     

A comparative study of the effect of morphactin and Niagara on the leaf epidermis

Treatment of two-week-oldBrassica campestris andTrigonella foenum-graecum plants with morphactin andVicia faba, Antirrhinum orontium, andPapaver somniferum with Niagara, induced marked variations in the orientation and ontogeny of stomata and the epiderma cells. Morphactin—chlorflurenol at 12.5, 62.5, 125, 250, and 500 ppm, caused marked damage of the shoot apices and changes in the epidermal tissue, such as divisions of the guard cells, reduction in the size of the stomata, and epidermal cells. Niagara—ethyl-hydrogen-1-propylphosphonate at 100, 500, 1 000 5 000, and 10 000 ppm caused thickenings of the epidermal cell walls and differentiation of new meristemoids from the epidermal cells, contiguous stomata, and incomplete development of the guard cells.     

Stomatal movement and potassium transport in epidermal strips of Zea mays: The effect of CO2

Summary The correlation between stomatal action and potassium movement in the epidermis of Zea mays was examined in isolated epidermal strips floated on distilled water. Stomatal opening in the isolated epidermis is reversible in response to alternate periods of light or darkness, and is always correlated with a shift in the potassium content of the guard cells. K accumulates in guard cells during stomatal opening, and moves from the guard cells into the subsidiary cells during rapid stomatal closure. When epidermal strips are illuminated in normal air, as against CO₂-free air, the stomata do not open and there is a virtually complete depletion of K from the stomatal apparatus. In darkness CO₂-containing air inhibits stomatal opening and K accumulation in guard cells, but does not lead to a depletion of K from the stomata as observed in the light.     

Changes in minimal diffusive resistances of leaf epidermes during ageing of primary leaves of phaseolus vulgaris L.

Minimal diffusive resistances of both leaf epidermes increased during normal and retarded ageing (moving secondary leaves aside, plant decapitation). The retarded ageing of primary leaves slowed down increase in epidermal resistance (r_ep), and was also reflected in the prolongation of their growth, increase of leaf area, size of epidermal and guard cells and stomatal pores. Decrease of stomata density was to some extent balanced by an increase in the pore size; the later rapid rise in diffusion resistance was induced by the loss of stomata ability to open fully.     

Boron deficiency affects cell morphology and structure of young leaves of radish

Boron (B) is an essential microelement for the growth and development of plants. B-deficient radish plants grew slowly compared to B-sufficient controls. Soluble B and cell wall-bound B decreased in young leaves on removal of B from culture medium. In old leaves, B deficiency reduced soluble B content but there was no significant effect on cell wall-bound B content compared to controls. The mesophyll cells in the middle of leaves were enlarged abnormally and had greater cell wall thickness under B-deficient conditions. B deficiency reduced the stomata frequency, inhibited the stomata aperture, and guard cells had thickened cell walls. B-starved leaves showed decreased photosynthesis and stomatal conductance. These indicate that B deficiency could interfere with cell wall development, especially irregular guard cell walls as a result of B deficiency severely affected the rhythmic stomatal closing and opening, preventing the normal functioning of stomata. Correspondingly, photosynthesis was indirectly affected, and plant growth decreased.     

Abnormal Stomatal Behaviour and Hormonal Imbalance in flacca, a Wilty Mutant of Tomato: EFFECT OF ABSCISIC ACID AND AUXIN ON STOMATAL BEHAVIOUR AND PEROXIDASE ACTIVITY

The wilty tomato mutant flacca and the normal variety RheinlandsRuhm were compared in terms of: (1) potassium transport intoand out of the guard cells, (2) cell wall properties which includeprotein, hydroxyproline and peroxidase activity, and (3) activityof indol-3yl-acetic acid oxidase. Also studied were the effectsof auxin on stomatal behaviour and peroxidase activity whenapplied to normal plants during development, and the short-termeffect of abscisic acid on the resistance of flacca stomatato closure under plasmolysis. Potassium transport, wall protein and hydroxyproline all seemedto be equal in mutant and normal plants. Peroxidase activitywas higher in the soluble and wall fractions of the mutant,and decreased toward normal in the mutant treated with abscisicacid. More stomata were open and peroxidase activity was higherin normal plants treated with auxin during development. Thepercentage of open stomata under plasmolysis was lower and theiraperture size was smaller in the epidermal strips taken fromabscisic-acid-treated mutant plants than from control mutantplants.     

GFP-mTn融合蛋白对蓝猪耳生活细胞微丝骨架的标记

用农杆菌介导法将嵌合基因GFP-mTn(mTn是微丝结合蛋白Talin的微丝结合域,可以显示活体细胞中微丝的结构)导入蓝猪耳.经激光共聚焦显微镜观察了转基因植株的各种不同组织中融合蛋白的表达和分布情况.在叶片的表皮细胞、保卫细胞、根部的皮层细胞中有融合蛋白的不同程度表达.但仅在保卫细胞中微丝标记状况良好,显示基因表达的组织特异性.经光诱导处于开放态的气孔的保卫细胞微丝呈网状结构,在细胞内无规则分布;经黑暗诱导处于关闭态的气孔保卫细胞中微丝束沿保卫细胞纵轴排列,呈卷曲状分布,并观察到螺旋和环状的微丝结构.在转基因植株的其他部位,例如茎表皮细胞、根毛细胞和花粉粒中,未检测到目的基因的表达.本研究获得的转基因植株为研究气孔运动过程中微丝动态变化提供了有用的材料.     

Protein Tyrosine Phosphatases Mediate the Signaling Pathway of Stomatal Closure of Vicia faba L.

The regulation of stomatal movement is one of the most important signaling networks in plants.The H -ATPase at the plasma membrane of guard cells plays a critical role in the stomata opening, while there are some conflicting results regarding the effectiveness of the plasma membrane H -ATPase inhibitor,vanadate, in inhibiting stomata opening. We observed that 2 mmol/L vanadate hardly inhibited light-stimulated stomata opening in epidermal peels of Viciafaba L., but significantly inhibited dark- and ABA-induced stomatal closure. These results cannot be explained with the previous findings that H -ATPase was inhibited by vanadate. In view of the fact that vanadate is an inhibitor of protein tyrosine phosphatases (PTPases),we investigated whether the stomatal movement regulated by vanadate is through the regulation of PTPase.As expected, phenylarsine oxide (PAO), a specific inhibitor of PTPase, has very similar effects and even more effective than vanadate. Typical PTPase activity was found in guard cells of V. faba; moreover, the phosphatase activity could be inhibited by both vanadate and PAO. These results not only provide a novel explanation for conflicting results about vanadate modulating stomatal movement, but also provide further evidence for the involvement of PTPases in modulating signal transduction of stomatal movement.