Stomatal Dimensions Research Articles

Morpho-physiological characterization of second generation colchiploids in sweet orange (<i>Citrus sinensis </i>(L.) Osbeck) cv. Mosambi

Induction of tetraploidy in citrus is commonly meant for the development of triploid seedless cultivars as well as resistance against abiotic and biotic stresses. Three-year-old, 20 second-generation colchicine treated (0.05, 0.10, 0.15 and 0.20%) plants (colchiploids), established from the putative tetraploid branches of the first generation colchiploids of sweet orange (Citrus sinensis (L.) Osbeck) cv. Mosambi vegetatively propagated on Jatti khatti rootstock, along with their wild (parent) type, were characterized based on morphological and physiological traits. Plant height and canopy volume were reduced, but stem girth, nodes per shoot and bark: wood increased in the majority of the second-generation colchiploids related to the wild type. Colchiploids also possessed improved flower characteristics in terms of length and width. The stomatal dimensions increased, but stomatal concentration reduced in all the colchiploids. Colchicine treatment also caused significant variations in leaf gas exchange parameters, including photosynthetic rate, intercellular CO2 concentration, leaf net transpiration rates, stomatal conductance, and intrinsic water use efficiency in colchiploids affecting their photosynthetic activities. The solid tetraploids identified on the basis of morpho-physiological characterization can be used in future breeding programmes for the development of triploid seedless citrus cultivars or can be used for the mitigation of biotic and abiotic stresses.

Morpho-physiological characterization of second generation colchiploids in sweet orange (<i>Citrus sinensis </i>(L.) Osbeck) cv. Mosambi

Induction of tetraploidy in citrus is commonly meant for the development of triploid seedless cultivars as well as resistance against abiotic and biotic stresses. Three-year-old, 20 second-generation colchicine treated (0.05, 0.10, 0.15 and 0.20%) plants (colchiploids), established from the putative tetraploid branches of the first generation colchiploids of sweet orange (Citrus sinensis (L.) Osbeck) cv. Mosambi vegetatively propagated on Jatti khatti rootstock, along with their wild (parent) type, were characterized based on morphological and physiological traits. Plant height and canopy volume were reduced, but stem girth, nodes per shoot and bark: wood increased in the majority of the second-generation colchiploids related to the wild type. Colchiploids also possessed improved flower characteristics in terms of length and width. The stomatal dimensions increased, but stomatal concentration reduced in all the colchiploids. Colchicine treatment also caused significant variations in leaf gas exchange parameters, including photosynthetic rate, intercellular CO2 concentration, leaf net transpiration rates, stomatal conductance, and intrinsic water use efficiency in colchiploids affecting their photosynthetic activities. The solid tetraploids identified on the basis of morpho-physiological characterization can be used in future breeding programmes for the development of triploid seedless citrus cultivars or can be used for the mitigation of biotic and abiotic stresses.

Evaluation of Relationships between Stomatal Dimensions and Density with the Root System in Bread Wheat Cultivars and Lines under Rainfed Conditions

Evaluation of Relationships between Stomatal Dimensions and Density with the Root System in Bread Wheat Cultivars and Lines under Rainfed Conditions

Investigation of the morphological, physiological, biochemical, and catabolic characteristics and gene expression under drought stress in tolerant and sensitive genotypes of wild barley [Hordeum vulgare subsp. spontaneum (K. Koch) Asch. & Graebn.

BackgroundBarley (H. vulgare L.) is an important cereal crop cultivated across various climates globally. Barley and its ancestor (H. vulgare subsp. spontaneum) are an economically valuable model for genetic research and improvement. Drought, among various abiotic stresses, is a substantial threat to agriculture due to its unpredictable nature and significant impact on crop yield.ResultsThis study was conducted in both greenhouse and laboratory settings. Prior to the study, wild barley accessions were pre-selected based on their sensitivity or tolerance to drought as determined from fieldwork in the 2020–2021 and 2021–2022 cropping seasons. The effects of three levels of drought stress were evaluated (control, 90–95% field capacity [FC]; mild stress, 50–55% FC; and severe stress, 25–30% FC). Several parameters were assessed, including seedling and root growth, enzymatic activity (CAT, SOD, POD), soluble protein levels, chlorophyll content, carotenoids, abaxial and adaxial stomatal density and dimensions, and relative gene expression of Dhn1, SOD, POD, and CAT. Drought stress significantly increased enzyme activities, especially at 25–30% FC, and more in the tolerant genotype. On the other hand, sensitive genotypes showed a notable increase in stomatal density. Under drought stress, there was a general decline in seedling and root growth, protein content, chlorophyll and carotenoids, and stomatal dimensions. Importantly, gene expression analysis revealed that Dhn1, SOD, POD, and CAT were upregulated under drought, with the highest expression levels observed in the drought-tolerant genotype under severe stress conditions (25–30% FC).ConclusionsOur investigation highlights the distinct morphological, physiological, biochemical, and gene-expression profiles of drought-resistant and drought-sensitive wild barley genotypes under varying degrees of drought.

Stomatal dimensions of Laguncularia racemosa leaves in restored and degraded mangrove ecosystems

ABSTRACT Mangrove leaves have adapted to effectively manage water conservation and regulate toxic saline conditions through the morphological characteristics of stomatal dimensions. The present study examines the stomatal dimensions of 120 Laguncularia racemosa leaves from both a degraded mangrove ecosystem and a restored mangrove ecosystem located along the Guyana coastline. Datasets were obtained during the wet and dry seasons using the nearest individual sampling method. The nail polish blotting technique, microscopy, and digital photography were used to obtain measurements of various stomatal dimensions, including guard cell length and width, pore length and width, circumference, surface area, stomatal frequency, density, index, and epidermal cell frequency. Our hypothesis is that there is significant variation in the stomatal dimensions of Laguncularia racemosa leaves as a function of mangrove ecosystem type and seasonal change. The results of this study confirmed this hypothesis as significant variations were observed in stomatal dimensions as a function of seasonal changes and mangrove ecosystem type. Statistically significant differences (p < 0.05, R > 0.70) were observed between the degraded ecosystem during the dry season and the restored ecosystem during the wet season, specifically regarding guard cell length and width, pore length and width, area, and circumference. Multiple regression analysis and PCA provide compelling evidence to support the existence of robust correlations between ecosystem types and stomatal dimensions. The results of our study indicate that the leaves of Laguncularia racemosa display certain small-scale adjustments that enable them to manage the stress factors present in different ecosystems and seasons.

Anatomical and histochemical adaptations of Melpomene peruviana to the xeric environment of high altitudes

Melpomene peruviana is one of the ecologically toughest fern species that prospers under climatically extreme conditions between 3400-5200 meters above sea level and occasionally in dry areas at lower elevations. To gain a better understanding of the adaptations that allow this species to withstand such extreme environmental conditions, we investigated the anatomy and histochemistry of the sporophyte of three populations of M. peruviana. All plant organs exhibited thick cuticles, and vascular bundles surrounded by a ring or cap of sclereids and suberized endodermis. Roots also showed an exodermis with U-shaped thickening. The sclereids and the chlorenchyma of the leaf mesophyll were rich in phenolic compounds. Tannins were detected in the spongy parenchyma close to the vascular bundles of the leaf. Hydathodes revealed a cutinized endodermal layer and the presence of flavonoids, lipidic/terpenoid droplets, and free sugars in the epidermis and parenchyma cells. Rhizome scales had basal idioblasts and apical clavate glands with complex contents rich in phenolic compounds, lipids, terpenes, mucilaginous polysaccharides and proteins. Some of the observed morpho-anatomical characteristics such as microphylly, small stomata in high densities, thick cuticles and sclerenchyma close to the vascular tissue, reduce water loss by evapotranspiration and correspond to typical xeromorphic fern features. Among the histochemical characteristics, mucilaginous polysaccharides may act as gels to absorb and retain water while phenolic compounds are recognized for their antioxidant activity. The three populations exhibited a remarkable uniformity concerning their histochemical assays, stomatal dimensions and densities, and tissue thickness. The anatomy and histochemistry of M. peruviana are described for the first time, highlighting morphoanatomical and histochemical characteristics that act as key adaptations to xeric environmental conditions.

Response of Anatomical Characteristics of Nile Flower Eichhornia crassipes to Environmental Changes and their Impact on Tigris Water Quality

The current study was conducted on the Tigris River in the distance between Qayyarah district of Nineveh province and Baiji district of Salahuddin province by five stations (Al-Gayyarah, Jisr Al-Shirgat, Asdeira, Al-Zuwia and Almsahag). Anatomical Characteristics of Nile flower Eichhornia crassipes were studied. Some qualitative properties of river water were studied. The results indicated that there were significant differences between the study stations in all anatomical characteristics of the plant, Significant differences were found in the different study stations in all the characteristics of the upper and lower skin of the leaves of the Nile flower plants, it is the dimensions of stomata and its index and the average dimensions of the cells of the upper and lower skin. For the stems of the Nile flower plants, anatomical characteristics showed significant differences with different study stations. Al- Mosahak station achieved the highest stomatal dimensions of 15 and 13 μm for length and width respectively. Al-Gayyarah station excelled in the highest averages of the stomata index and average length × width of normal cells with values of 14 and 32 × 15 μm respectively. The highest mean of the physical characteristics of the river water was 1407 mg / L of total dissolved solids at the Al-Zuwia station in December, 8.4 for pH at Al-Gayyarah and Jisr Al-Shirgat stations during January, and 1.4 mg / L for BOD5 in Al-Gayyarah station during March, 2.3 mg / L for total hardness at Asdira station in February, 1.02 mg / L of nitrate at Almsahag station in December, 1.231 mg / L for sulfate at Al-Gayyarah station in January, 2.38 mg / L for sodium at Al-Zauwia station in December, and 1.2 mg / L for potassium at Almsahag station in March.

Bna.EPF2 Enhances Drought Tolerance by Regulating Stomatal Development and Stomatal Size in Brassica napus

Drought stress severely affects global plant growth and production. The enhancement of plant water-use efficiency (WUE) and drought tolerance by the manipulation of the stomata is an effective strategy to deal with water shortage. However, increasing the WUE and drought tolerance by manipulation on the stomata has rarely been tested in Brassica napus. Here, we isolated Bna.EPF2, an epidermal patterning factor (EPF) in Brassica napus (ecotype Westar), and identified its role in drought performance. Bna.EPF2 overexpression lines had a reduction average of 19.02% in abaxial stomatal density and smaller stomatal pore size, leading to approximately 25% lower transpiration, which finally resulted in greater instantaneous WUE and enhanced drought tolerance. Interestingly, the reduction in stomatal density did not affect the CO2 assimilation or yield-related agronomic traits in Bna.EPF2 overexpression plants. Together with the complementation of Bna.EPF2 significantly decreasing the stomatal density of Arabidopsis epf2, and Bna.EPF2 being expressed in mature guard cells, these results suggest that Bna.EPF2 not only functions in stomatal density development, but also in stomatal dimension in Brassicas. Taken together, our results suggest that Bna.EPF2 improves WUE and drought tolerance by the regulation of stomatal density and stomatal size in Brassica without growth and yield penalty, and provide insight into the manipulation of this gene in the breeding of drought tolerant plants with increased production under water deficit conditions.

Specific Sound Frequency Improves Intrinsic Water Efficiency in Rice Leaf by Imparting Changes in Stomatal Dimensions

Various attempts have been made to increase rice production, including breeding for high-yielding and stress-tolerant varieties, a good crop management system, and increased agricultural input in rice production. Soundwave stimulation has been demonstrated to affect plant growth; thus, this method can be employed in the current rice production methods to improve yield. The study aims to determine the effects of different sound wave qualities on the general growth, physiological, and morphological of rice seedlings. Rice seeds of the MR219 variety were grown under a glasshouse condition in a nested design with five replications and were stimulated with various sound wave frequencies. Various sound wave frequencies, 380, 359, 357, 353, and 350 Hz, were obtained by placing the pot at varying distances (80, 160, 240, 320, and 400 cm, respectively) from the sound source, except control treatment. There were significant effects in some of the parameters: plant height, leaf physiology, and stomatal pore and length when treated with varying sound wave qualities. Plants can be stimulated with 380, 357, and 350 Hz soundwaves frequencies for the best photosynthetic experience. In addition, 359 Hz of sound wave stimulation resulted in high water use efficiency, which is beneficial in improving crop performance in drought conditions. Thus, it was demonstrated that the sound wave stimulation method has the potential to enhance rice performance in addition to the regular agronomic practices of rice production in farmers’ fields.

PECTIN METHYLESTERASE INHIBITOR18 functions in stomatal dynamics and stomatal dimension.

Pectin methylesterification in guard cell (GC) walls plays an important role in stomatal development and stomatal response to external stimuli, and pectin methylesterase inhibitors (PMEIs) modulate pectin methylesterification by inhibition of pectin methylesterase (PME). However, the function of PMEIs has not been reported in stomata. Here, we report the role of Arabidopsis (Arabidopsis thaliana) PECTIN METHYLESTERASE INHIBITOR18 in stomatal dynamic responses to environmental changes. PMEI18 mutation increased pectin demethylesterification and reduced pectin degradation, resulting in increased stomatal pore size, impaired stomatal dynamics, and hypersensitivity to drought stresses. In contrast, overexpression of PMEI18 reduced pectin demethylesterification and increased pectin degradation, causing more rapid stomatal dynamics. PMEI18 interacted with PME31 in plants, and in vitro enzymatic assays demonstrated that PMEI18 directly inhibits the PME activity of PME31 on pectins. Genetic interaction analyses suggested that PMEI18 modulates stomatal dynamics mainly through inhibition of PME31 on pectin methylesterification in cell walls. Our results provide insight into the molecular mechanism of the PMEI18-PME31 module in stomatal dynamics and highlight the role of PMEI18 and PME31 in stomatal dynamics through modulation of pectin methylesterification and distribution in GC walls.

Plant Growth Regulators Mediated Changes in the Growth, Photosynthesis, Nutrient Acquisition and Productivity of Mustard

Plant growth regulators (PGRs) are naturally occurring signaling molecules that modulate numerous phenological traits and physicochemical features of plants throughout their life cycles. Exogenous supplementation of PGRs is an effective strategy for improving the productivity of important agricultural crops. This research was planned to evaluate the effects of six PGRs, namely indole-3-acetic acid (IAA), 24-epibrassinolide (EBL), gibberellic acid (GA3), putrescine (put), salicylic acid (SA) and triacontanol (Tria), on morphology, photosynthesis, nutrient acquisition, and the yield and quality characteristics of three mustard cultivars, i.e., Chutki, Nath Sona, and Rohini. Two foliar sprays each of water, IAA (10−6 M), EBL (10−6 M), GA3 (10−5 M), put (10−3 M), 10−5 M SA, and Tria (10−6 M) were applied to plants at fifty and seventy days after sowing (DAS). The crops’ phenological, physicochemical and microscopic parameters were evaluated at ninety DAS, and yield characteristics were evaluated at harvest (120 DAS). The observations of this study indicated that foliar feeding with PGRs increased all studied parameters, relative to water-spray treatment. The Nath Sona cultivar displayed a stronger response than Rohini and Chutki. Among the leaf-applied PGRs, 24-EBL, followed by IAA and GA3, proved the most effective and improved all the studied parameters. Moreover, the exogenous application of PGRs, especially EBL, significantly enhanced stomatal dimensions and root cell longevity. Treatment with EBL enhanced plant dry weight by 34.7, 35.4, and 37.6%, the net photosynthetic rate by 65.3, 64.7, and 60.2%, seed yield per plant by 67.1, 65.2, and 67.3%, and oil yield per plant by 42.6, 48.2, and 41.1%, in the Chutki, Nath Sona, and Rohini cultivars, respectively, relative to the water-spray treatment. It may be concluded that of the tested PGRs, 24-EBL proved most effective at enhancing the morphological, physicochemical, and yield features of the mustard cultivars.

Plant density effects on quinoa yield, leaf anatomy, ultrastructure and gas exchange

AbstractTo study the impact of plant density onChenopodium quinoa(c.v. CICA-17) achene yield and its relationship with morphology, leaf anatomy and gas exchange in the absence of water stress, field trials were conducted at 1995 m asl in Northwestern Argentina. Two plant densities were evaluated; low density (LD) 7.2 plants/m (120 240 pl/ha) and high density (HD) 27.9 plants/m (465 930 pl/ha). HD treatment caused light competition, inducing morphological and anatomical changes in Quinoa plants. Plants grown under HD conditions showed decreases in plant height and stem diameter, lower stomatal dimensions and densities, and thinner leaf blades. Compensation strategies such as increases in specific leaf area and a higher number chloroplasts per palisade cell were observed, nevertheless these changes did not fully compensate C absorption and gas exchange limitations, therefore limiting the uptake of N and P and resulting in a 53.2% lower yield of HD compared to LD. Considering the ability of quinoa plants to change its morphology and anatomy, further studies with intermediate plant densities are necessary in order to determine if it is possible to achieve higher yields and to increase the efficiency in the use of the resources.

A Deep Learning Method for Fully Automatic Stomatal Morphometry and Maximal Conductance Estimation.

Stomata are integral to plant performance, enabling the exchange of gases between the atmosphere and the plant. The anatomy of stomata influences conductance properties with the maximal conductance rate, gsmax, calculated from density and size. However, current calculations of stomatal dimensions are performed manually, which are time-consuming and error prone. Here, we show how automated morphometry from leaf impressions can predict a functional property: the anatomical gsmax. A deep learning network was derived to preserve stomatal morphometry via semantic segmentation. This forms part of an automated pipeline to measure stomata traits for the estimation of anatomical gsmax. The proposed pipeline achieves accuracy of 100% for the distinction (wheat vs. poplar) and detection of stomata in both datasets. The automated deep learning-based method gave estimates for gsmax within 3.8 and 1.9% of those values manually calculated from an expert for a wheat and poplar dataset, respectively. Semantic segmentation provides a rapid and repeatable method for the estimation of anatomical gsmax from microscopic images of leaf impressions. This advanced method provides a step toward reducing the bottleneck associated with plant phenotyping approaches and will provide a rapid method to assess gas fluxes in plants based on stomata morphometry.

Two galacturonosyltransferases function in plant growth, stomatal development, and dynamics.

The mechanical properties of guard cell (GC) walls are important for stomatal development and stomatal response to external stimuli. However, the molecular mechanisms of pectin synthesis and pectin composition controlling stomatal development and dynamics remain poorly explored. Here, we characterized the role of two Arabidopsis (Arabidopsis thaliana) galacturonosyltransferases, GAUT10 and GAUT11, in plant growth, stomatal development, and stomatal dynamics. GAUT10 and GAUT11 double mutations reduced pectin synthesis and promoted homogalacturonan (HG) demethylesterification and demethylesterified HG degradation, resulting in larger stomatal complexes and smaller pore areas, increased stomatal dynamics, and enhanced drought tolerance of plants. In contrast, increased GAUT10 or GAUT11 expression impaired stomatal dynamics and drought sensitivity. Genetic interaction analyses together with immunolabeling analyses suggest that the methylesterified HG level is important in stomatal dynamics, and pectin abundance with the demethylesterified HG level controls stomatal dimension and stomatal size. Our results provide insight into the molecular mechanism of GC wall properties in stomatal dynamics, and highlight the role of GAUT10 and GAUT11 in stomatal dimension and dynamics through modulation of pectin biosynthesis and distribution in GC walls.

Plasticidade dos estômatos em folhas de Ichthyothere terminalis (Spreng) Blake (Asteraceae) em diferentes estações do ano

O Cerrado possui a flora diversificada que ocorre em diferentes fisionomias. Uma das características marcantes do bioma é a ocorrência de estações chuvosa e seca bem definidas. Durante a seca as plantas do Cerrado estão sujeitas à restrição de água. Os estômatos, que são estruturas epidérmicas responsáveis pelas trocas gasosas, são essenciais para a manutenção do estado hídrico das plantas. Ichthyothere terminalis (Spreng.) Blake é uma Asteraceae herbácea frequente nas formações abertas do Cerrado. A espécie possui sistema subterrâneo espessado, que contribui para persistência da planta no ambiente. No final da seca, ocorre a rebrota dos órgãos aéreos. O objetivo deste trabalho foi o de avaliar as dimensões dos estômatos em folhas de Ichthyothere terminalis em diferentes épocas do ano. Foram realizadas coletas em fisionomias abertas do Cerrado em períodos secos e chuvosos, nos quais as plantas estavam em diferentes fases fenológicas. As folhas foram coletadas, preservadas e fixadas seguindo métodos usuais para análises anatômicas e histométricas. As epidermes foram destacadas e as medições e contagens foram feitas em microscópio de luz. As folhas de Ichthyothere terminalis são anfiestomáticas, com maior densidade estomática na face abaxial. A densidade de estômatos na face abaxial foi maior na transição entra as estações seca e chuvosa. A área dos poros estomáticos foi maior no início da seca nas duas faces epidérmicas. A espécie mostrou capacidade de alterar os atributos dos estômatos em diferentes estações, e isso pode contribuir para sua ocorrência em habitats sujeitos à seca sazonal.

Novel perspectives on stomatal impressions: Rapid and non-invasive surface characterization of plant leaves by scanning electron microscopy.

Scanning electron microscopy (SEM) is widely used to investigate the surface morphology, and physiological state of plant leaves. Conventionally used methods for sample preparation are invasive, irreversible, require skill and expensive equipment, and are time and labor consuming. This study demonstrates a method to obtain in vivo surface information of plant leaves by imaging replicas with SEM that is rapid and non-invasive. Dental putty was applied to the leaves for 5 minutes and then removed. Replicas were then imaged with SEM and compared to fresh leaves, and leaves that were processed conventionally by chemical fixation, dehydration and critical point drying. The surface structure of leaves was well preserved on the replicas. The outline of epidermal as well as guard cells could be clearly distinguished enabling determination of stomatal density. Comparison of the dimensions of guard cells revealed that replicas did not differ from fresh leaves, while conventional sample preparation induced strong shrinkage (-40% in length and -38% in width) of the cells when compared to guard cells on fresh leaves. Tilting the replicas enabled clear measurement of stomatal aperture dimensions. Summing up, the major advantages of this method are that it is inexpensive, non-toxic, simple to apply, can be performed in the field, and that results on stomatal density and in vivo stomatal dimensions in 3D can be obtained in a few minutes.

CHICKEN MANURE AND LUMINOUS AVAILABILITY INFLUENCE GAS EXCHANGE AND PHOTOCHEMICAL PROCESSES IN Alibertia edulis (Rich.) A. Rich SEEDLINGS

Information on the physiological responses of native plants from the Brazilian Cerrado regarding the use of chicken manure and luminosities are important for their silvicultural management. Thus, aimed to evaluate the effect of chicken manure and luminous availability on the photosynthetic metabolism of Alibertia edulis (Rich) A. Rich. The experiment was carried out in pots, testing five doses of chicken manure – CM (0.00, 2.08, 4.16, 6.24 and 8.32 g kg-1) incorporated at Dystroferric Red Latosol, and two luminous environmental (full sun and 50% shaded). The higher CO2 assimilation rate, stomatal conductance and carboxylation efficiency of Rubisco occurred in seedlings grown in full sun. The seedlings showed higher photochemical indicators in photosystem II in the shaded and with addition of 8.32 g kg-1 of CM. The intercellular CO2 concentration in leaves was lower with addition of 5.55 g kg-1 of CM. The leaves presented larger stomatal dimensions under shaded. The cultivation of A. edulis in full sun and the addition of about 4.16 g kg-1 of CM favored greater stomatal regulation and CO2 assimilation.

Evaluation of Bread Wheat (&lt;i&gt;Triticum aestivum&lt;/i&gt; L.) Genotypes for Drought Tolerance through Selection Indices

The current study was planned to identify drought tolerant bread wheat genotypes based on physiological and yield traits. In this context, a set of 12 genotypes (Sarsabz, NIA-Sundar, NIA-Amber, Sassui, Khirman, Marvi-2000, NIA-Sarang, Kiran-95, NIA-Sunheri, Bhittai, Bathoor-08 and Tatara) were evaluated under normal and water stress conditions. Mean squares from analysis of variance exhibited that genotypes, treatments and genotype x treatment interaction showed significant differences (P&lt;0.05) for majority of the studied traits, indicating that there is significant variations are existed for physio-yield traits; therefore these genotypes may be preferred for further breeding programs in respect to drought stress. Regarding reduction percentage of genotypes under drought stress against normal water conditions, the minimum reduction was observed in Bathoor-08 for spike length and flag leaf area, Kiran-95 for grain yield plant, NIA-Sundar for seed index, Marvi-2000 for relative water content, Sarsabz for grains spike, whereas maximum but desirable reduction of stomatal dimension and density was displayed by Sarsabz and Tatara under water stress conditions, respectively. On the basis of drought tolerant indices, the genotypes Kiran-95, NIA-Sundar and Sarsabz showed lower values for tolerance index (TOL), trait stability index (TSI) and stress susceptibility (SSI), nevertheless it is believed that lower values of these indices show the less reduction in yield and its related traits due to water stress conditions hence can be tagged as tolerant genotypes for drought. Correlation results revealed that MP, SSI, TOL and TSI indices were correlated with grain yield under two conditions and they can be the appropriate indices for screening wheat genotypes.

Haploid Induction in Multiplier Onion (Allium cepa var aggregatum) through in vitro Gynogenesis

The haploid induction study is an effective method for inbred and hybrid development quickly. The optimization of media composition for specific indigenous genotypes was a critical factor. Two media namely, Gamborg’s medium (B5) and Murashige and Skoog’s medium (MS) with six different combinations of plant growth regulators were used to evaluate the gynogenic potential of six different genotypes of multiplier onion. Days for embryo induction was earlier in Acc. 1 (46-54), whereas Acc. 4 was the best responding genotype with a higher percent of embryo induction (0.76) followed by Acc. 15 (0.48). The embryo induction rate and survival rate of 0.21% and 54.54% respectively were recorded in B5 medium whereas in MS medium the induction and survival rate was 0.34 % and 34.86 % respectively. Embryo induction ranged from 0 to 1.41% in this study. Five haploids and one mixoploid in B5 medium, five haploids in MS medium were obtained. Ploidy status of the plants was confirmed by flow cytometry, cell cytology, and stomatal dimension analysis..

Hornwort stomata do not respond actively to exogenous and environmental cues.

Because stomata in bryophytes occur on sporangia, they are subject to different developmental and evolutionary constraints from those on leaves of tracheophytes. No conclusive experimental evidence exists on the responses of hornwort stomata to exogenous stimulation. Responses of hornwort stomata to abscisic acid (ABA), desiccation, darkness and plasmolysis were compared with those in tracheophyte leaves. Potassium ion concentrations in the guard cells and adjacent cells were analysed by X-ray microanalysis, and the ontogeny of the sporophytic intercellular spaces was compared with those of tracheophytes by cryo-scanning electron microscopy. The apertures in hornwort stomata open early in development and thereafter remain open. In hornworts, the experimental treatments, based on measurements of >9000 stomata, produced only a slight reduction in aperture dimensions after desiccation and plasmolysis, and no changes following ABA treatments and darkness. In tracheophytes, all these treatments resulted in complete stomatal closure. Potassium concentrations are similar in hornwort guard cells and epidermal cells under all treatments at all times. The small changes in hornwort stomatal dimensions in response to desiccation and plasmolysis are probably mechanical and/or stress responses of all the epidermal and spongy chlorophyllose cells, affecting the guard cells. In contrast to their nascent gas-filled counterparts across tracheophytes, sporophytic intercellular spaces in hornworts are initially liquid filled. Our experiments demonstrate a lack of physiological regulation of opening and closing of stomata in hornworts compared with tracheophytes, and support accumulating developmental and structural evidence that stomata in hornworts are primarily involved in sporophyte desiccation and spore discharge rather than the regulation of photosynthesis-related gaseous exchange. Our results run counter to the notion of the early acquisition of active control of stomatal movements in bryophytes as proposed from previous experiments on mosses.