Guard Cell Size Research Articles

Stomatal dynamics in Alloteropsis semialata arise from the evolving interplay between photosynthetic physiology, stomatal size and biochemistry.

C4 plants are expected to have faster stomatal movements than C3 species because they tend to have smaller guard cells. However, little is known about how the evolution of C4 photosynthesis influences stomatal dynamics in relation to guard cell size and environmental factors. We studied photosynthetically diverse populations of the grass Alloteropsis semialata, showing that the origin of C4 photosynthesis in this species was associated with a shortening of stomatal guard and subsidiary cells. However, for a given cell size, C4 and C3-C4 intermediate individuals had similar or slower light-induced stomatal opening speeds than C3 individuals. Conversely, when exposed to decreasing light, stomata in C4 plants closed as fast as those in non-C4 plants. Polyploid formation in some C4 plants led to larger stomatal cells and was associated with slower stomatal opening. Conversely, diversification of C4 diploid plants into wetter environments was associated with an acceleration of stomatal opening. Overall, there was significant relationship between light-saturated photosynthesis and stomatal opening speed in the C4 plants, implying that photosynthetic energy production was limiting for stomatal opening. Stomatal dynamics in this wild grass therefore arise from the evolving interplay between photosynthetic physiology and the size and biochemical function of stomatal complexes.

Effects of Decapitation, Water-Deficit Stress, and Pot Size on Morpho-Anatomy and Physiology of Pterocarpus indicus

The interacting effects of stem decapitation, water-deficit stress, and pot size on the growth, morpho-anatomical, and physiological traits of Pterocarpus indicus seedlings were analyzed in this study. Changes in root collar diameter (RCD), biomass allocation, number of leaflets (NL), mean leaf area, guard cell size, stomatal aperture size, phloem cap fiber (PCF) thickness, xylem vessel density (XVD), relative leaf water content (RWC), stomatal conductance (gsw), transpiration rate (E), fluorescence quantum yield, transpiration (E), photosynthesis (PN), and electron transport rate (ETR) of decapitated and undecapitated P. indicus seedlings in different pot sizes (small, medium, large) and watering regimes (every 2, 7, and 14 days) were analyzed. The decapitation × water-deficit stress × and pot size interaction did not affect growth and morpho-anatomical variables, but they did on most of the physiological traits. Decapitated seedlings watered every 14 days and planted in medium or large pots have lower gsw, PN, E, and RWC. While the RCD of large-potted and water-stressed (every 14 days) seedlings decreased, allocations to stem and fine roots increased. Moreover, the NL and PCF significantly decreased, while the ETR and XVD significantly increased in decapitated and water-stressed seedlings. Overall, the decapitation-watering interaction caused significant stress to P. indicus seedlings. Keywords: biomass allocations, decapitation, drought stress, multiple stress, xylem vessel density

Stomata variation in the process of polyploidization in Chinese chive (Allium tuberosum).

Stomatal variation, including guard cell (GC) density, size and chloroplast number, is often used to differentiate polyploids from diploids. However, few works have focused on stomatal variation with respect to polyploidization, especially for consecutively different ploidy levels within a plant species. For example, Allium tuberosum, which is mainly a tetraploid (2n = 4x = 32), is also found at other ploidy levels which have not been widely studied yet. We recently found cultivars with different ploidy levels, including those that are diploid (2n = 2x = 16), triploid (2n = 3x = 24), pseudopentaploid (2n = 34-42, mostly 40) and pseudohexaploid (2n = 44-50, mostly 48). GCs were evaluated for their density, size (length and width) and chloroplast number. There was no correspondence between ploidy level and stomatal density, in which anisopolyploids (approximately 57 and 53 stomata/mm2 in triploid and pseudopentaploid, respectively) had a higher stomatal density than isopolyploids (approximately 36, 43, and 44 stomata/mm2 in diploid, tetraploid and pseudohexaploid, respectively). There was a positive relationship between ploidy level and GC chloroplast number (approximately 44, 45, 51, 72 and 90 in diploid to pseudohexaploid, respectively). GC length and width also increased with ploidy level. However, the length increased approximately 1.22 times faster than the width during polyploidization. This study shows that GC size increased with increasing DNA content, but the rate of increase differed between length and width. In the process of polyploidization, plants evolved longer and narrower stomata with more chloroplasts in the GCs.

Somatic Embryogenesis Induction and Genetic Stability Assessment of Plants Regenerated from Immature Seeds of Akebia trifoliate (Thunb.) Koidz

Akebia trifoliata is a perennial woody plant with considerable potential in nutrition, food, and health, and the production of seedlings with high quality is critical for its economic utilization. Plant regeneration through somatic embryogenesis is a powerful alternative for propagating many plant species. In this study, a simple and practicable protocol was developed for plant regeneration from immature seeds of A. trifoliata via somatic embryogenesis, and the genetic stability of regenerated plants was also assessed. In the somatic embryo (SE) induction stage, the highest frequency of somatic embryogenesis (35.2%) was observed on the WPM medium containing 1.0 mg L−1 of thidiazuron (TDZ) and 1.0 mg L−1 of 6-benzyladenine (6-BA). The concentration of 6-BA was optimized at 1.0 mg L−1 for the proliferation and maturation of the induced SEs, and the combination of 2.0 mg L−1 of indole-3-butyric acid (IBA) and 0.5 mg L−1 of TDZ was the most responsive for root development and plant growth. The leaf morphological characteristics greatly varied among the established plants, and they could be grouped into three plant types, namely the normal type, Type Ι, and Type ΙΙ. Remarkable differences in the number, size, shape, and color of the leaflets were observed among the three types, while their ploidy level was the same via flow cytometry analysis. The Type ΙΙ and the Type Ι plants had the highest and the lowest net photosynthesis rate, transpiration rate, and stomatal conductance among the three groups, respectively, and both had a smaller size of stomatal guard cells than the normal type. Simple sequence repeat (SSR) analysis detected that 41 bands (43.62%) were different from those observed in the wild, indicating a high degree of polymorphism between the regenerants and their donor parent. The obtained plants might hold potential for future genetic improvement and breeding in A. trifoliata, and the established regeneration protocol might serve as a foundation for in vitro propagation and germplasm preservation of this crop.

Evolution of genome size and GC content in the tribe Carduinae (Asteraceae)

Genome size and GC content are basic species-specific attributes often delimiting genera or higher taxa, which enable the identification of polyploidy, hybridization and other modes of genome or karyotype evolution. The evolution of these genomic traits can often occur as a result of the selective pressure of the environment. Here, we reconstruct the evolution of these genomic traits in subtribe Carduinae (Asteraceae) in the context of changes in chromosome numbers. Using flow cytometry, genome size and GC content were estimated for 119 taxa and mapped onto a phylogenetic tree constructed using sequences from seven genetic markers. In addition, the genomic data were compared with the length of stomatal guard cells and achene size (length, weight) to evaluate the extent to which genomic characters could evolve adaptively in this subtribe. We found strong phylogenetic signals for the analysed genomic and phenotypic traits, which delimited most Carduinae genera or clades in agreement with the reconstructed phylogeny. Monoploid genome size was positively correlated with genomic GC content and stomatal guard cell length. In Cirsium, whose species were the focus of the majority of the analyses, the large-genomed subgen. Lophiolepis had smaller guard cells, which might be related to it occurring in more xeric habitats compared to subgen. Cirsium. In contrast, the achenes of the large-genomed subgen. Lophiolepis were larger, possibly in response to the summer drought, whereas achene weight and length were independent of genome size across the subtribe. Thus, genome size in the subtribe Carduinae might evolve under weak environmental control, at least under that mediated by the size of guard cells or achenes. Achene size was related positively to GC content, which could have evolved adaptively in response to summer drought. In Carduus and the North American Cirsium taxa, there is an increase in average chromosome size with reduction in monoploid chromosome number, suggesting descending dysploidy associated with chromosomal fusion. Polyploidy is relatively rare in this subtribe and was confirmed only in five of the species studied, including Cirsium vulgare, an invasive species that likely originated via distant (intersubgeneric) hybridization, as suggested by its intermediate genomic and achene features combined with the conflict between its morphology and phylogenetic position. Phylogenetic reconstruction, differences in genomic parameters, as well as stomatal guard cell and achene sizes support the separation of a monophyletic Lophiolepis from the remainder of Cirsium. Genome and achene size results also indicate that the early diverging Cirsium italicum can be separated from the rest of the monophyletic Lophiolepis+Picnomon+Notobasis clade.

Diverse mangroves deviate from other angiosperms in their genome size, leaf cell size and cell packing density relationships.

While genome size limits the minimum sizes and maximum numbers of cells that can be packed into a given leaf volume, mature cell sizes can be substantially larger than their meristematic precursors and vary in response to abiotic conditions. Mangroves are iconic examples of how abiotic conditions can influence the evolution of plant phenotypes. Here, we examined the coordination between genome size, leaf cell sizes, cell packing densities and leaf size in 13 mangrove species across four sites in China. Four of these species occurred at more than one site, allowing us to test the effect of climate on leaf anatomy. We found that genome sizes of mangroves were very small compared to other angiosperms, but, like other angiosperms, mangrove cells were always larger than the minimum size defined by genome size. Increasing mean annual temperature of a growth site led to higher packing densities of veins (Dv) and stomata (Ds) and smaller epidermal cells but had no effect on stomatal size. In contrast to other angiosperms, mangroves exhibited (1) a negative relationship between guard cell size and genome size; (2) epidermal cells that were smaller than stomata; and (3) coordination between Dv and Ds that was not mediated by epidermal cell size. Furthermore, mangrove epidermal cell sizes and packing densities covaried with leaf size. While mangroves exhibited coordination between veins and stomata and attained a maximum theoretical stomatal conductance similar to that of other angiosperms, the tissue-level tradeoffs underlying these similar relationships across species and environments were markedly different, perhaps indicative of the unique structural and physiological adaptations of mangroves to their stressful environments.

Induction of polyploids in acid lime (Citrus aurantifolia) through colchicine treatment of in vitro derived shoot tip explants

AbstractPolyploid breeding is an effective tool to induce variability in the existing population, specifically in the crops having very narrow genetic base such as acid lime. Hence, an experiment was conducted to induce polyploidy in acid lime through colchicine treatment. Higher frequency of triploids were obtained in 250 μM colchicine treatment (27.27%), whereas combination of 3× (21.42%), 4× (13.33%) and aneuploid (6.67%) were induced at 500 μM colchicine treatment. Measurement of stomatal density and guard cell size of colchiploids revealed that the former one has negative relation with ploidy level and a positive relation was observed between guard cell size and ploidy level. Further, area and size of nuclei also had a positive relation with ploidy level. Hence, stomatal density, guard cell and nuclei size can be used effectively as morphological marker for preliminary polyploid screening. From the experiment, it can be concluded that 500 μM colchicine treatment of in vitro derived shoot tip explants of acid lime is optimum for creating maximum possible variability through polyploidization in the existing acid lime population.

Leaf wettability, anatomy and ultra-structure of Nothofagus antarctica and N. betuloides grown under a CO2 enriched atmosphere

Increasing CO2 air concentration may affect wettability, anatomy and ultra-structure of leaves of Patagonian forest species, evergreen and deciduous plants potentially responding differently to such CO2 increases. In this study, we analysed the wettability, anatomy and ultra-structure of leaves of Nothofagus antarctica (deciduous) and N. betuloides (evergreen) grown under high CO2 concentrations. Leaf wettability was affected by increasing CO2, in different directions depending on species and leaf side. In both species, soluble cuticular lipid concentrations per unit leaf area raised with higher CO2 levels. Stomatal parameters (density, size of guard cells and pores) showed different responses to CO2 increasing depending on the species examined. In both species, leaf tissues showed a general trend to diminish with higher CO2 concentration. Cuticle thickness was modified with higher CO2 concentration in N. betuloides, but not in N. antarctica leaves. In both species, chloroplasts were often damaged with the increase in CO2 concentration. Our results show that several surface and internal leaf parameters can be modified in association with an increase in atmospheric CO2 concentration which may very among plant species.

Enhanced morphologic traits and medicinal constituents of octaploids in Satureja mutica, a high-yielding medicinal savory

Satureja mutica is a tetraploid and perennial semi-bushy plant cultivated for different medicinal purposes. To induce polyploidy, two-leafed seedlings were exposed to different concentrations (0.00, 0.05, 0.1, and 0.2 % w/v) and durations (6, 12, and 24 h) of colchicine. The seedlings were then transferred to a culture medium for recovery and propagation. After clones were prepared from each seedling, octaploid clones were identified using flow cytometry. Chromosome counting was also used to confirm flow cytometric results in tetraploid (2n = 4x = 60; 2C DNA= 1.90 ± 0.01 pg) and octaploid (2n = 8x = 120; 2C DNA= 3.82 ± 02 pg) plants. The highest polyploidy induction efficiency with 32% was related to 0.05 % colchicine and 12 h duration. The results showed that the phenotypic traits of anatomical (stomata size, leaf guard cell size), morphological (stem diameter, length, width, and leaf area), physiological (soluble sugars, phenols, and flavonoids), and phytochemical (essential oil yield, P-cymene, γ-Terpinene, α-Thujene, and α-Pinene) properties significantly increased in octaploid plants, while the density of leaf stomata decreased compared to tetraploid plants. Our results verified that octaploid induction in Satureja mutica is an effective breeding method, remarkably increasing the quantitative and qualitative characteristics, which could be used as a new genetic resource in future breeding programs.

Production of Doubled Haploid through Anther Culture of the Male-Fertile Lines in the CMS System of Eggplant with the Cytoplasm of <i>Solanum grandifolium</i>

To produce doubled haploid homozygous male-sterile line of eggplant with the cytoplasm of Solanum grandifolium, anther culture of the male-fertile (MF) BC5 in the S. grandifolium induced CMS system was done. Anthers were cultured in an embryo induction medium and were heated to 35℃ for 3 d in the dark and then transferred to 25℃ under a 16 h photoperiod. After 20 d the anthers were transferred to a germination medium. The presence of pollen in the anther, number of chromosomes in the root tip cells, size of the stomatal guard cells and pollen fertility of the regenerated plants were investigated. The frequency of embryo formation in the MF line was 1.02%. From the embryos, one regenerated plant showed pollen non-formation type male sterility. Root tip chromosome number and stomatal guard cell size confirmed that the regenerated male-sterile plant is a microspore originated doubled haploid through spontaneous chromosome doubling. The present study demonstrates the first successful production of a doubled haploid homozygous male-sterile line in a CMS system of eggplant with the cytoplasm of S. grandifolium. Therefore, this material could be a useful breeding material for eggplant and improve the speed of conventional breeding.

Light and scanning electron microscopic comparative studies of geminivirus infected and healthy Eclipta alba (L.).

Eclipta alba (L.) is a valuable medicinal plant. However, its medicinal efficacy can be affected by geminivirus infection. Therefore, identification of healthy specimen is essential before to use as medicine. The present study provided the taxonomic characterization of geminivirus infected and healthy E. alba plant by studying apparent morphology and microscopic features through light and scanning electron microscopy. Before taxonomic characterization infected and healthy specimens were separated through molecular detection of geminivirus. Results of morphological studies reported that geminivirus infected E. alba plant showed systematic symptoms of infection like stunted growth, distortion and chlorosis of leaves, decrease in size of root, shoot and fruit, and so forth in comparison to healthy specimen. Anatomical findings reported that in both plants anomocytic and anisocytic types of stomata with multicellular warty trichomes were present. However, variations were observed in quantitative measures such as size of trichomes, epidermal, subsidiary and guard cells. Palynological observations identifies that both plants possessed tricolporate type of pollen but variation was mainly observed in size and shape of pollen, thickness of exine and intine, P/E ratio, pore size, interspecific difference, size of colpi, and pollen ornamentation. Overall this study concluded that both healthy and infected E. alba do not reported much variations in qualitative taxonomic features, but can be differentiated in terms of quantitative taxonomic evidences. Future studies are recommended for pharmacological analysis of both healthy and virus infected plants. RESEARCH HIGHLIGHTS: Eclipta alba has incredible therapeutic worth, but due to geminivirus infection the plant is affecting badly. Hence, the present studies give a comprehensive taxonomic report on the geminivirus infected and healthy plant species.

Implications of foliar epidermal micromorphology using light and scanning electron microscopy: A useful tool in taxonomy of Korean irises

The genus Iris L., comprising approximately 210 species, is one of the most species-rich genera in the family Iridaceae. In this study, the first comprehensive leaf micromorphological characters of Korean irises were studied using light and scanning electron microscopy. Our objective was to evaluate the foliar micromorphological characteristics (namely epidermal cells, stomata types, and guard cell size) of Korean Iris taxa in a systematic context. All the investigated Korean Iris taxa had amphistomatic or hypostomatic leaves with anomocytic stomatal complexes. Guard cell length varied among species, ranging from 24.8μm (I. rossii) to 56.0μm (I. domestica). Although the presence of papillae on the outer periclinal wall is not of taxonomic significance, leaf margin pattern, guard cell size, and sunken stomata type were useful for species-level identification of Korean Iris species. The occurrence of polymorphic stomatal types was reported here for the first time, and the correlation between genome size and epidermal guard cell length was discussed.

Papaya Leaf Curl Virus (PaLCuV) Infection on Papaya (Carica papaya L.) Plants Alters Anatomical and Physiological Properties and Reduces Bioactive Components.

Papaya leaves are used frequently for curing scores of ailments. The medicinal properties of papaya leaves are due to presence of certain bioactive/pharmacological compounds. However, the papaya leaf curl virus (PaLCuV), a geminivirus, is a major threat to papaya cultivation globally. During the present investigation, we observed that PaLCuV infection significantly altered the anatomy, physiology, and bioactive properties of papaya leaves. As compared to healthy leaves, the PaLCuV-infected leaves were found to have reduced stomatal density (76.83%), stomatal conductance (78.34%), photosynthesis rate (74.87%), water use efficiency (82.51%), chlorophyll (72.88%), carotenoid (46.63%), osmolality (48.55%), and soluble sugars (70.37%). We also found lower enzymatic activity (superoxide dismutase (SOD), ascorbate peroxidase (APX), and catalase (CAT)—56.88%, 85.27%, and 74.49%, respectively). It was found that the size of guard cells (50%), transpiration rate (45.05%), intercellular CO2 concentration (47.81%), anthocyanin (27.47%), proline content (74.17%), malondialdehyde (MDA) (106.65%), and electrolyte leakage (75.38%) was elevated in PaLCuV-infected leaves. The chlorophyll fluorescence analysis showed that the infected plant leaves had a significantly lower value of maximal quantum yield of photosystem II (PSII (Fv/Fm), photochemical quantum yield of photosystem I (PSI (Y(I)), and effective quantum yield of PSII (Y(II)). However, in non-photochemical quenching mechanisms, the proportion of energy dissipated in heat form (Y(NPQ)) was found to be significantly higher. We also tested the bioactivity of infected and healthy papaya leaf extracts on a Caenorhabditis elegans (C. elegans) model system. It was found that the crude extract of papaya leaves significantly enhanced the life span of C. elegans (29.7%) in comparison to virus-infected leaves (18.4%) on application of 100 µg/mL dose of the crude extract. Our research indicates that the PaLCuV-infected leaves not only had anatomical and physiological losses, but that pharmacological potential was also significantly decreased.

Characterization of anatomical foliar epidermal features of herbaceous flora of Tilla Jogian, Pakistan by using light microscopy techniques

In current study, 22 herbaceous plant specimens have been examined with the help of light microscope to carry out leaf epidermal anatomy. Foliar micro-morphology of herbaceous plants from Tilla Jogian, Jhelum Pakistan was held first time. The plants were collected from different parts of Tilla Jogian at different elevations. The main objective of the study is to use this information as an aid in plant taxonomy. Significant variations were observed in both qualitative and quantitative features. With the help of microscopy significant variations in characters like stomata size, number, epidermal cell size, shape and number, guard cell size, trichomes, and subsidiary cells were recorded. On the basis of these findings, light microscopy of leaf epidermal anatomical features holds great interest for taxonomists to identify complete taxa. Foliar epidermal anatomy of herbaceous flora serves as baseline data along with taxonomical data and can be helpful in demarcation and limitation of nearly associated taxa to gain better use of anatomical characters.

Growth of Micropropagated Solanum tuberosum L. Plantlets under Artificial Solar Spectrum and Different Mono- and Polychromatic LED Lights

In agriculture, LED light sources have increasingly replaced the standard luminescent lamps and have acquired an important role in plant micropropagation. We studied the effect of different light sources such as narrow-band LEDs (bright blue, blue, green, yellow, deep red, and red) and wide-band LEDs (cold white, white, warm white, full spectrum, and an artificial solar spectrum sun box constructed by us) on development of potato plantlets in vitro. White luminescent lamps were used as a control. The light intensity of 49 µmol · m−2 · s−1 was provided in all light treatments. We showed that the long-wave narrow-band light treatments were inapplicable for potato micropropagation, because plantlets were weak with small leaves, inhibited roots, and significantly elongated stems. Blue lights provided growth of shortened plantlets with large leaves, well-growing roots, and abundant green mass. The chlorophyll content was lower under blue and bright blue light and was at the same level in the remained treatments. Significant differences in the stomatal apparatus development were observed depending on the light source. These differences were not always reflected in the plantlet phenotype: e.g., plantlets under blue and bright blue lights showed no differences in any characteristics except stomatal density and size of stomatal guard cells. We found no significant effect of blue light portion in the white lights and full spectrum on plantlet growth. An artificial solar spectrum sun box was the most suitable for potato micropropagation, because it supported the development of plantlets with good fitness, uniform internodes length, abundant roots and green mass accumulation.

Tetraploid induction in savory (Satureja khuzistanica): cytological, morphological, phytochemical and physiological changes

Satureja khuzitanica, due to having phenolic compounds such as carvacrol in its essential oil and rosmarinic acid in its extract has strong antioxidant and antimicrobial properties and remarkable effects for treating several diseases. In this study, polyploidy induction was performed using 0.00, 0.05, 0.10, and 0.20% (w/v) colchicine and three treatment duration of 6, 12, and 24 h on one-week-old seedlings. Treated seedlings were transplanted to the medium culture and were regenerated. After three regenerations, tetraploid clones were identified by flow cytometry technique and chromosome counting. 2C DNA values in diploid (2n = 2x = 30) and induced tetraploid (2n = 4x = 60) were 1.43 ± 0.02 pg and 2.61 ± 03 pg, respectively. The highest tetraploid induction efficiency was 30%, obtained by colchicine concentration of 0.05% and the treatment duration of 6 h. The morphological, physiological, and phytochemical characteristics were measured in diploid and autotetraploid plants. Most of the studied traits in tetraploid plants including leaf length and width, stem diameter, stomata size, area, density, leaf guard cell size, flavonoid, phenol, soluble sugar, and essential oil yield increased significantly but stomata density decreased. In conclusion application of tetraploid induction in S. khuzistanica could be used to increase the quantity of secondary metabolites. It also can be promising to introduce a new genotype with higher phenolic compounds and drug effectiveness. The successful tetraploid induction of Khuzistan savory led to an increase in morphological parameters, biomass, essential oil yield, and phenolic compounds.

Comparative Analysis of Morphology, Photosynthetic Physiology, and Transcriptome Between Diploid and Tetraploid Barley Derived From Microspore Culture.

Polyploids play an important role in the breeding of plant for superior characteristics, and many reports have focused on the effects upon photosynthesis from polyploidization in some plant species recently, yet surprisingly little of this is known for barley. In this study, homozygous diploid and tetraploid plants, derived from microspore culturing of the barley cultivar “H30,” were used to assess differences between them in their cellular, photosynthetic, and transcriptomic characteristics. Our results showed that tetraploid barley has the distinct characteristics of polyploids, namely thicker and heavier leaves, enlarged stomata size or stomatal guard cell size, and more photosynthetic pigments and improved photosynthesis (especially under high light intensity). This enhanced photosynthesis of tetraploid barley was confirmed by several photosynthetic parameters, including net photosynthetic rate (Pn), stomatal conductance (Gs), intercellular CO2 concentration (Ci), transpiration rate (Tr), maximum net photosynthetic rate (Pmax), light saturation point (LSP), maximum RuBP saturated rate carboxylation (Vcmax), and maximum rate of electron transport (Jmax). Transcriptomic analyses revealed that just ~2.3% of all detected genes exhibited differential expression patterns [i.e., differentially expressed genes (DEGs)], and that most of these – 580 of 793 DEGs in total – were upregulated in the tetraploid barley. The follow-up KEGG analysis indicated that the most enriched pathway was related to photosynthesis-antenna proteins, while the downregulation of DEGs was related mainly to the light-harvesting cholorophyII a/b-binding protein (Lhcb1) component, both validated by quantitative PCR (qPCR). Taken together, our integrated analysis of morphology, photosynthetic physiology, and transcriptome provides evidences for understanding of how polyploidization enhances the photosynthetic capacity in tetraploids of barley.

Natural Diversity in Stomatal Features of Cultivated and Wild Oryza Species

BackgroundStomata in rice control a number of physiological processes by regulating gas and water exchange between the atmosphere and plant tissues. The impact of the structural diversity of these micropores on its conductance level is an important area to explore before introducing stomatal traits into any breeding program in order to increase photosynthesis and crop yield. Therefore, an intensive measurement of structural components of stomatal complex (SC) of twenty three Oryza species spanning the primary, secondary and tertiary gene pools of rice has been conducted.ResultsExtensive diversity was found in stomatal number and size in different Oryza species and Oryza complexes. Interestingly, the dynamics of stomatal traits in Oryza family varies differently within different Oryza genetic complexes. Example, the Sativa complex exhibits the greatest diversity in stomatal number, while the Officinalis complex is more diverse for its stomatal size. Combining the structural information with the Oryza phylogeny revealed that speciation has tended towards increasing stomatal density rather than stomatal size in rice family. Thus, the most recent species (i.e. the domesticated rice) eventually has developed smaller yet numerous stomata. Along with this, speciation has also resulted in a steady increase in stomatal conductance (anatomical, gmax) in different Oryza species. These two results unambiguously prove that increasing stomatal number (which results in stomatal size reduction) has increased the stomatal conductance in rice. Correlations of structural traits with the anatomical conductance, leaf carbon isotope discrimination (∆13C) and major leaf morphological and anatomical traits provide strong supports to untangle the ever mysterious dependencies of these traits in rice. The result displayed an expected negative correlation in the number and size of stomata; and positive correlations among the stomatal length, width and area with guard cell length, width on both abaxial and adaxial leaf surfaces. In addition, gmax is found to be positively correlated with stomatal number and guard cell length. The ∆13C values of rice species showed a positive correlation with stomatal number, which suggest an increased water loss with increased stomatal number. Interestingly, in contrast, the ∆13C consistently shows a negative relationship with stomatal and guard cell size, which suggests that the water loss is less when the stomata are larger. Therefore, we hypothesize that increasing stomatal size, instead of numbers, is a better approach for breeding programs in order to minimize the water loss through stomata in rice.ConclusionCurrent paper generates useful data on stomatal profile of wild rice that is hitherto unknown for the rice science community. It has been proved here that the speciation has resulted in an increased stomatal number accompanied by size reduction during Oryza’s evolutionary course; this has resulted in an increased gmax but reduced water use efficiency. Although may not be the sole driver of water use efficiency in rice, our data suggests that stomata are a potential target for modifying the currently low water use efficiency in domesticated rice. It is proposed that Oryza barthii can be used in traditional breeding programs in enhancing the stomatal size of elite rice cultivars.

Development and characterization of tetraploid castor plants

AbstractCastor is a prime industrial crop belonging to a monotypic genus and its genetic improvement depends on creating desired variability in the primary gene pool. This study reports the development of tetraploid castor plants through colchicine treatment. Seeds of three castor genotypes were soaked in aqueous solutions of colchicine with variable concentrations, and the LD50value was determined. Of 1010 treated field-raised plants, three were identified as potential polyploids based on increases in a guard cell size and reductions in the number of stomata. The putative polyploid plants were selfed and the progeny were subjected to meiotic analysis. All the progeny were found to be tetraploid. The pairing of chromosomes was abnormal with univalent to octavalent configurations during meiosis-I, but the later parts of meiosis were normal. Seasonal variations in pollen fertility indicated the possible role of temperature-sensitive male sterility in causing the sterility in tetraploid plants. The tetraploid plants were phenotypically comparable with their diploid counterparts, but produced substantially bigger seeds. Thus, these tetraploid plants are valuable resources for basic and applied research in castor.

Systematics of medicinally important weeds of genus Convolvulus: Convolvulaceae

Abstract Background: Palyno-morphological and foliar epidermal studies plays a very important role in the correct identification and differentiation of two weeds of genus convolvulus. Objective: The aim of the study is to determine the medicinal uses of the two important weeds for correct systematic identification. Methods: Both the qualitative and quantitative features were measured with the help of Light microscopy (LM) and scanning electron microscope (SEM). Results: Variations were observed in both the weeds, i.e Convolvulus arvensis (bindweeds) and Convolvulus prostatus (soft bindweed) in epidermal cells, stomatal size and number, guard cell shape and size, subsidiary cell and diversity of trichomes. Paracytic type of stomata was found in both the weed species. Stomata shape in Convolvulus arvensis is elliptical and oval to oval oblong in Convolvulus prostratus. Weed species have a difference in size, shape, polarity and exine ornamentation. Tricolporate pollen type was observed. The shape of pollen grains is Prolate, Perforate. By using these Palyno-morphological characteristics a taxonomic key is prepared for the identification of these weed plants. Conclusions: High fertility rate i.e Convolvulus arvensis 96% and in Convolvulus prostatus is 90 % shows the weed species are well adapted in the area. Systematics studies of the weed play a very important role not only incorrect identification but also differentiation with other weed plants and subsequently for the conservation purposes.