For the robust identification of taxonomically complex fern family like Athyriaceae, light and scanning electron microscopy is significance implications. This article present first microscopic investigation of foliar micromorphology of 3 genera and 10 species belonging to Athyriaceae namely, Athyrium, Deparia, and Diplazium were collected from different localities in Malakand Division , Northern Pakistan.
In present study we compare foliar micromorphology of all 10 species using standard protocols of light microcopy (LM) and scanning electron microscopy. Qualitative micromorphological variations in shape of epidermal cells, anticlinal wall pattern, stomatal type and shape, stomatal pore shape, guard cells shape, and trichomes types were studied.
In addition, some quantitative characters were also studied and data were statistically analyzed in epidermal cell size, stomatal size, stomatal pore size, stomatal density, and stomatal index.
The pivotal result of study include; shape of epidermal cell in all species is irregular on both abaxial and adaxial surfaces. The anticlinal walls are sinuous in most of the species but some species have irregular lobed and broadly lobed wall. Leaves are hypostomatic in all studied species.
Two main categories of stomatal type were found: polocytic and anomocytic. Unicellular nonglandular trichomes were observed in only one species Athyrium mackinnoni. The variation in foliar micromorphological characters between the genera and within the species was useful in identification and classification and have potential taxonomic significance for species differentiation. An identification key using micromor-phological characters are provided to distinguish genera and species.
Stomatal opening and closing was followed with a diffusion porometer in beech (Fagus grandi‐folia Ehrh.), maple (Acer rubrum L.), oak (Quercus rubra L.) and yellow poplar (Liriodendron tulipifera L.) in a situation where illuminance could be changed by placing shades over the trees.
In all four species the stomata opened quicker than they closed. The time to reach an equilibrium stomatal resistance was constant for a species but varied between species, for all changes in illuminance greater than 3000 ft‐candles.
To open to a constant leaf resistance took from 3 minutes in beech to 20 minutes in yellow poplar; oak and maple were intermediate at 12 minutes. Beech required 12 minutes to close to a constant leaf resistance, maple 18, oak 20, and yellow poplar 36 minutes.
When the change in illuminance was less than 3000 ft‐candles, the stomata took longer to reach a new equilibrium in all species except yellow poplar. Also beech stomata opened and closed in dimmer light than yellow poplar.
The rates of stomatal opening and closing correlated well with the known shade tolerance of the species.
Straight-chain saturated fatty acids (C6-C11) and abscisic acid (ABA) accumulate in the leaves of Phaseolus vulgaris L. and Hordeum vulgare L. under water stress.
ABA and certain of the fatty acids, particularly decanoic and undecanoic acid, can inhibit stomatal opening and cause stomatal closure in epidermal strips of Commelina communis L. depending on the incubating medium used. 10(-4) M (±)-ABA inhibits opening in media containing either high or relatively low concentrations of KCl but causes closure only in the latter medium.
The fatty acids (at 10(-4) M) prevent opening in both media while significant closure of open stomata was caused only by undecanoic acid in both media and, additionally, by decanoic acid in the low-KCl medium.
10(-4) M formic acid also caused stomatal closure and prevented opening to significant extents in the low-KCl medium (it was not tested in the high-KCl medium). The efficacy of undecanoic acid in causing 50% inhibition of opening is about three orders of magnitude lower than that of ABA.
At a concentration of 10(-3) M, nonanoic, decanoic and particularly undecanoic acid and all-trans-farnesol cause increased cell leakage in Beta vulgaris L. root tissue. Undecanoic acid (10(-4) M) also causes some loss of guard cell integrity in C. communis within 1.5 h of treatment.
ABA (10(-4) M) reduces transpiration rates in barley and C. communis leaves when applied via the transpiration stream but decanoic and undecanoic acids did not have this effect. Transpiration was not affected when ABA or the fatty acids were applied to the leaf surfaces.
Sucrose concentration in guard cells of epidermal strips of Commelina benghalensis increased with stomatal opening.
Sucrose uptake patterns were investigated using guard cell protoplasts of C. benghalensis. Sucrose (0.5 mM) uptake into these protoplasts was sensitive to pH, with an optimum at pH 6. Uptake of sucrose into guard cell protoplasts was inhibited by 2,4-dinitrophenol (DNP), diethylstilbestrol (DES) and (ptrifluoromethoxy)carbonyl cyanide phenylhydrozone (FCCP), while DCMU and o-phenanthroline had no effect on the uptake of sucrose.
Fusicoccin (FC) stimulated sucrose influx. The influence of pH and the effect of the metabolic inhibitors on the sucrose uptake into the guard cell protoplasts are consistent with an energy dependent membrane-function.
In solanaceous plants such as tomato and tobacco, the sucrose transporter SUT1 is crucial for phloem loading. Using GUS as a reporter, the promoter and other regulatory cis elements required for the tomato LeSUT1 expression were analyzed by heterologous expression of translational chimeric constructs in tobacco.
Although LeSUT1 is highly expressed at the RNA level, GUS expression under the control of a 1.8 kb LeSUT1 promoter resulted in few plants expressing GUS. In GUS-positive transformants, expression levels were low and limited to leaf phloem. Increasing or decreasing the length of LeSUT1 promoter did not lead to a significant increase in positive transformants or higher expression levels.
Translational fusion of GUS to the LeSUT1 C-terminus in a construct containing all exons and introns and the 3′-UTR led to a higher number of positive transformants and many plants with high GUS activity. LeSUT1 expression was detected in ab- and adaxial phloem companion cells, trichomes and guard cells.
The role of individual introns in LeSUT1 expression was further analyzed by placing each LeSUT1 intron into the 5′-UTR within the 2.3 kb LeSUT1 promoter construct. Results showed remarkable functions for the three introns for SUT1 expression in trichomes, guard cells and phloem cells.
Intron 3 is responsible for expression in trichomes, whereas intron 2 is necessary for expression in companion cells and guard cells. The combination of all introns is required for the full expression pattern in phloem, guard cells and trichomes.
• Guard cell movements are regulated by environmental cues including, for example, elevations in extracellular Ca2+ concentration. Here, the subcellular localization and physiological function of the Ca2+‐sensing receptor (CAS) protein was investigated.
• CAS protein localization was ascertained by microscopic analyses of green fluorescent protein (GFP) fusion proteins and biochemical fractionation assays. Comparative guard cell movement investigations were performed in wild‐type and cas loss‐of‐function mutant lines of Arabidopsis thaliana. Cytoplasmic Ca2+ dynamics were addressed in plants expressing the yellow cameleon reporter protein YC3.6.
• This study identified CAS as a chloroplast‐localized protein that is crucial for proper stomatal regulation in response to elevations of external Ca2+. CAS fulfils this role through modulation of the cytoplasmic Ca2+ concentration.
• This work reveals a novel role of the chloroplast in cellular Ca2+ signal transduction.
Eukaryotic anion/proton exchangers of the CLC (chloride channel) family mediate anion fluxes across intracellular membranes.
The Arabidopsis thaliana anion/proton exchanger AtCLCa is involved in vacuolar accumulation of nitrate. We investigated the role of AtCLCa in leaf guard cells, a specialized plant epidermal cell that controls gas exchange and water loss through pores called stomata.
We showed that AtCLCa not only fulfilled the expected role of accumulating anions in the vacuole during stomatal opening but also mediated anion release during stomatal closure in response to the stress hormone abscisic acid (ABA).
We found that this dual role resulted from a phosphorylation-dependent change in the activity of AtCLCa. The protein kinase OST1 (also known as SnRK2.6) is a key signaling player and central regulator in guard cells in response to ABA. Phosphorylation of Thr(38) in the amino-terminal cytoplasmic domain of AtCLCa by OST1 increased the outward anion fluxes across the vacuolar membrane, which are essential for stomatal closure.
We provide evidence that bidirectional activities of an intracellular CLC exchanger are physiologically relevant and that phosphorylation regulates the transport mode of this exchanger.