Stomatal Frequency Research Articles

In vitro propagation, micromorphological studies and ex vitro rooting of Alternanthera philoxeroides (Mart.) Griseb.: an important aquatic plant

In vitro propagation methods using ex vitro rooting were developed for Alternanthera philoxeroides using nodal segments procured from mature plants. The explants were surface sterilized with 0.1 % HgCl2 solution and inoculated on semisolid Murashige and Skoog (MS) medium containing various concentrations and combinations of plant growth regulators. All the explants responded, and maximum 8.0 ± 0.4 shoots per node with 4.7 ± 0.7 cm average length were induced from nodal meristems on MS medium supplemented with 2.0 mg/L 6-benzylaminopurine (BAP). The shoots were further multiplied (23.8 ± 1.9 shoots per explant) by repeated subculture of freshly induced shoots on MS medium augmented with 1.0 mg/L each of BAP and Kinetin, 0.1 mg/L indole-3-acetic acid (IAA) and additives. About 85 % shoots were rooted (18.0 ± 0.8 roots per shoot) in vitro on half-strength MS medium fortified with 1.5 mg/L indole-3-butyric acid (IBA). Maximum 96 % shoots were rooted using ex vitro methods, and 7.3 ± 1.0 roots per shoot induced with IBA (300 mg/L). The in vitro as well as ex vitro rooted plantlets were acclimatized successfully in the greenhouse. Biologically significant developmental changes were observed during acclimatization of plantlets, particularly in leaf micromorphology in terms of changes in stomatal frequency and stomatal index. This knowledge helps in understanding the response of the plants toward changed environmental conditions during hardening process. This is the first report on micropropagation of A. philoxeroides using ex vitro rooting method which can be used for the large-scale multiplication of this medicinally important aquatic plant.

Multi-Year Leaf-Level Response to Sub-Ambient and Elevated Experimental CO2 in Betula nana.

The strong link between stomatal frequency and CO2 in woody plants is key for understanding past CO2 dynamics, predicting future change, and evaluating the significant role of vegetation in the hydrological cycle. Experimental validation is required to evaluate the long-term adaptive leaf response of C3 plants to CO2 conditions; however, studies to date have only focused on short-term single-season experiments and may not capture (1) the full ontogeny of leaves to experimental CO2 exposure or (2) the true adjustment of structural stomatal properties to CO2, which we postulate is likely to occur over several growing seasons. We conducted controlled growth chamber experiments at 150 ppmv, 450 ppmv and 800 ppmv CO2 with woody C3 shrub Betula nana (dwarf birch) over two successive annual growing seasons and evaluated the structural stomatal response to atmospheric CO2 conditions. We find that while some adjustment of leaf morphological and stomatal parameters occurred in the first growing season where plants are exposed to experimental CO2 conditions, amplified adjustment of non-plastic stomatal properties such as stomatal conductance occurred in the second year of experimental CO2 exposure. We postulate that the species response limit to CO2 of B. nana may occur around 400–450 ppmv. Our findings strongly support the necessity for multi-annual experiments in C3 perennials in order to evaluate the effects of environmental conditions and provide a likely explanation of the contradictory results between historical and palaeobotanical records and experimental data.

Balancing Water Uptake and Loss through the Coordinated Regulation of Stomatal and Root Development.

Root development is influenced by nutrient and water availabilities. Plants are able to adjust many attributes of their root in response to environmental signals including the size and shape of the primary root, lateral roots and root hairs. Here we investigated the response of roots to changes in the levels of leaf transpiration associated with altered stomatal frequency. We found that plants with high stomatal density and conductance produce a larger rooting area and as a result have enhanced phosphate uptake capacity whereas plants with low stomatal conductance produce a smaller root. Manipulating the growth environment of plants indicated that enhanced root growth is most likely a result of an increased demand for water rather than phosphate. Plants manipulated to have an increase or reduction in root hair growth show a reduction or increase respectively, in stomatal conductance and density. Our results demonstrate that plants can balance their water uptake and loss through coordinated regulation of both stomatal and root development.

In Vitro Segregation of Tetraploid and Octoploid Plantlets from Colchicine-induced Ploidy Chimeras in Echinacea purpurea L.

Echinacea purpurea L. is one of the important ornamental and medicinal plant species. Ploidy manipulation is a valuable tool for improving plant quality or production in E. purpurea as well as in many other plants. To study the segregation of pure ploidy plantlets from colchicine-induced ploidy chimeras in E. purpurea, we used a chimera plantlet that consisted of 1.93% diploid, 35.04% tetraploid, and 63.03% octoploid cells as the source material for experiments. The results showed that three factors significantly influenced the segregation, i.e., the component ratios of different ploidy cells in the chimera, the number of sequential passages, and the methods of segregation culture of the chimera plantlets. Other factors, such as explant types (i.e., leaf, petiole, or root) and 6-benzyladenine (BA) concentrations (i.e., 0.2, 0.4, 0.8, and 1.2 mg·L−1) occasionally influenced the segregation. Pure chromosome-doubled polyploids are not easily obtained in various plant species, so segregation culture of ploidy chimeras may potentially be more effective. The morphological characteristic and content of cichoric acid were compared among diploid, tetraploid, and octoploid plants. Results indicated that tetraploid and octoploid plants had more stunted growth, larger stomata, lower stomata frequency, more chloroplast number in guard cells, and higher cichoric acid content than original diploid lines.

The occurrence of <italic>Quercus heqingensis</italic> n. sp. and its application to palaeo-CO<sub>2</sub> estimates

Many leaf fossils belonging to Quercus sect. Heterobalanus were collected from the Upper Pliocene Sanying Formation in Heqing County, Yunnan Province, China. Leaves are oblong, elliptic or obovate with entire margin or spinous serrations, 3.1–8.7 cm in length and 1.8–5.7 cm in width. Leaf apex is round, mucronate or blunt round, while leaf base is heart-shaped, slightly heart-shaped or blunt round, and occasionally asymmetric. The petiole is slightly sturdy, straight or a bit curved, with 1.8–4.9 mm in length. The main vein of these specimens is slightly zigzagging, with a sturdy base attenuating to the apex. Secondary veins are pinnate, 7–12 pairs, alternate and parallel with the stretching angles from 40° to 73°, bifurcating near 1/3 to 1/2 of the leaf margin. Tertiary veins are, relatively thin, 5–7 bands in 1 cm2, and perpendicular to secondary veins. Quaternary, blind and marginal veins are not clear. The upper epidermis has both unicellular and multicellular trichomes without stomata, and most of the epidermal cells are nearly quadrangular. The lower epidermis has only unicellular trichomes and cyclocytic stomatal apparatuses, and the epidermal cells are nearly quadrangular or pentagonal. The stomatal apparatuses are 20–33 m m in length, 17–27 m m in width , with 2–6 m m wide in apertures. They spread casually with the stomatal density of 503±98 mm - 2 and the stomatal index of 8.90%±0.32%. The guard cells show kidney-shaped, with 5–7 subsidiary cells. These features are similar to Q. rehderiana, Q. guyavifolia , Q. preguyavifolia and some other extant or fossil species of Q . sect. Heterobalanus , but they are different in terms of density and type of trichomes. Both Q . guyavifolia and Q . preguyavifolia have more trichomes in total, and multicellular trichomes in lower epidermis which spread in veins and between veins. The fossil leaves of Q . sect. Heterobalanus in Heqing and Q . rehderiana have less trichomes, and the former has no multicellular trichome in lower epidermis, while the latter’s multicellular trichome are just found in veins. Hence, it was designated as a new species— Quercus heqingensis n. sp. The estimates of palaeoatmospheric-CO2 using the positive relationships between stomatal frequency and atmospheric CO2 partial pressure in its Nearest Living Relatives (NLRs)— Q . guyavifolia show that, the palaeo-CO2 levels in the late Pliocene reconstructed by Q. heqingensis were 263.42±24.86 ppm (equation with extant field collections) and 234.25±22.49 ppm (equation with historical herbarium samples). These results are slightly lower than most previous estimates of the same age. Our results are in agreement with other estimates when palaeoaltitude is considered. This indicates that it is feasible to apply the stomatal index of Q . heqingensis to the positive relationship between stomatal index of Q . guyavifolia and atmospheric p CO2 to reconstruct palaeo-CO2 levels. Meanwhile, the results further support lower palaeo-CO2 level in the late Pliocene than present. This study provides credible evidence for future palaeo-CO2 estimates using NLRs as proxies.

Evaluación morfoanatómica de hojas “D” de piña (Ananas comosus (L.) Merr. var. comosus) en respuesta a la implantación de dos sistemas de cultivo en Corrientes, Argentina

<p>Una posibilidad concreta para cultivar especies de origen tropical en el subtrópico es compensar el problema de las bajas temperaturas con la utilización de coberturas plásticas, las cuales modifican el ambiente y las respuestas del cultivo. El objetivo del presente trabajo fue evaluar morfoanatómicamente las hojas “D” de plantas de piña que crecen en diferentes condiciones de cultivo, vinculando aspectos de diferenciación en sus características morfológicas, anatómicas y ecofisiológicas en relación a las estaciones del año. Se evaluó durante las cuatro estaciones del año y en dos sistemas de cultivo, el área foliar, peso fresco y seco, espesor de lámina, capacidad de retención de agua, cantidad de espinas y el contenido de clorofila. En adición a lo anterior, se realizaron cortes histológicos para comparar las características morfoanatómicas. Se comprueba que las condiciones ambientales bajo cobertura aumentan el área foliar, peso seco y peso fresco de las hojas “D” durante y luego de las estaciones frías respecto de aquellas cultivadas a campo. Las hojas cultivadas bajo cobertura, presentan mayor densidad estomática, mayor cantidad de casquetes fibrosos pero menor espesor de lámina y menor espesor de parénquima acuífero y clorofiliano, respecto a aquellas que crecieron en condiciones de campo, indicando plasticidad fenotípica.</p>

Anatomía foliar relacionada con la ruta fotosintética en árboles de café (Coffea arabica L., var. Caturra Rojo) expuestos a diferentes niveles de radiación solar en la Sierra Maestra, Granma, Cuba

<p>Se diseñó un experimento de campo con el objetivo de investigar el efecto de diferentes niveles de exposición solar (Pleno sol, Sombra regulada y Sombra no regulada) sobre la anatomía foliar de árboles de café (<em>Coffea arabica</em> L., var. Caturra Rojo) en una localidad de la Sierra Maestra, en la provincia Granma, Cuba. Se realizaron estudios histológicos y morfológicos foliares que incluyeron el área foliar de hojas individuales, el grosor de la lámina foliar, de los parénquimas en empalizada y esponjoso, de las epidermis abaxial y adaxial, la densidad y las dimensiones de los estomas. Los resultados demuestran que bajo condiciones de pleno sol, el cafeto muestra características de aclimatación determinadas por una disminución en el área foliar, incremento del grosor histológico foliar, del parénquima de empalizada, de la epidermis abaxial, así como de la frecuencia estomática. En todos los niveles de exposición solar se observó en las células del haz envolvente gran cantidad de cloroplastos. El crecimiento de hojas individuales independientemente del nivel de exposición solar estuvo relacionado con las precipitaciones, siendo las hojas de plantas crecidas a pleno sol de menor área foliar. Las hojas emitidas durante los meses más calientes del año y durante la fase de fructificación fueron más pequeñas.</p>

Research Advances on Leaf and Wood Anatomy of Woody Species of a Tamaulipan Thorn Scrub Forest and its Significance in Taxonomy and Drought Resistance

The present paper make a synthesis of a comparative leaf anatomy including leaf surface, leaf lamina, petiole and venation as well as wood anatomy of 30 woody species of a Tamaulipan Thorn Scrub, Northeastern Mexico. The results showed a large variability in anatomical traits of both leaf and wood anatomy. The variations of these anatomical traits could be effectively used in taxonomic delimitation of the species and adaptation of the species to xeric environments. For example the absence or low frequency of stomata on leaf surface, the presence of long palisade cells, and presence of narrow xylem vessels in the wood could be related to adaptation of the species to drought. Besides the species with dense venation and petiole with thick collenchyma and sclerenchyma and large vascular bundle could be well adapted to xeric environments. It is suggested that a comprehensive consideration of leaf anatomy (leaf surface, lamina, petiole and venation) and wood anatomy should be used as a basis of taxonomy and drought resistance.

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.

Nitrous oxide emission and mitigation from wheat agriculture: association of physiological and anatomical characteristics of wheat genotypes.

Agriculture is an important source of emission of the greenhouse gas nitrous oxide (N2O). The observed differences in N2O emission among different varieties of agricultural crops can be a key factor for developing N2O emission reduction strategies. N2O emissions were estimated from three varieties of wheat viz. Sonalika, DBW 39, and K 0307 during 2010-2011 in an attempt to identify plant physiological and anatomical factors contributing to differences in gas emissions within the varieties. Sonalika was identified as a low N2O emitting variety and DBW 39 as high emitting when grown in a uniform field condition. The experiment was repeated in 2011-2012 selecting low emitting Sonalika and high emitting variety DBW 39 for further confirmation of the results obtained during the first year of experimentation. Important plant factors namely rate of photosynthesis and transpiration in flag leaf, stomatal frequency of adaxial flag leaf surface, and size of the xylem vessels (mean vessel size of node, stem, and root) were studied, and their relationship with N2O flux was worked out. A good correlation between transpiration and N2O flux was observed in this study. Scanning electron microscopic investigation revealed strong association of flag leaf stomatal frequency and xylem size with N2O emission. Sonalika, identified as low N2O emitting variety during both the years of study, also recorded higher grain yield due to its higher efficiency of photosynthate allocation toward the developing grains. The observed differences in N2O emission are considered to be due largely to genetic differences in the wheat genotypes.

STUDIES ON NATURAL DIVERSITY AND IN VITRO BEHAVIOR OF RARE INDIAN MEDICINAL HERB 'SAFED MUSLI' (CHLOROPHYTUM BORIVILIANUM)

Chlorophytum borivilianum Sant. et Fernand. (‘Safed Musli’), belonging to monocotyledonous family Liliaceae. It is distributed throughout the tropical and sub- tropical parts of the world. In India it has been reported growing in parts of Rajasthan, Madhya Pradesh, Jharkhand, Chhattisgarh, Maharashtra and Gujarat. It is an endangered Indian medicinal herb, valued for its tuberous roots reputed to have aphrodisiac properties. The plant is of economic importance in India since its dried roots are currently sold in the market at a price of Rs. 1500/- (US$30) per kilogram. Due to large-scale and indiscriminate collection of wild material and insufficient attempts either to allow its replenishment or its cultivation, C. borivilianum is rapidly disappearing. The natural regeneration of this herb is through tuberous roots that have become scarce in nature. It is therefore necessary to understand genetic structure of its natural populations in view of aiming at conservation and improvement strategies. In present study seven accessions of C. borivilianum were collected from different geographical regions of India were assessed for their natural diversity and in vitro behavior. The accessions exhibited significant variations in selected parameters of leaf growth, stomatal frequency, flowering and yield of root tubers. Accessions PBL-4, PBL-6 and PBL-7 outperformed the growth and yield parameters as compared to others. Higher magnitude of phenotypic coefficient of variation (PCV) and genotypic coefficient of variation (GCV) was recorded for yield per plant and leaf characteristics. More than 92.0% habitability was recorded for all the traits studied except stomatal frequency and number of flower, the other traits have positive correlation with yield per plant. In vitro response of these accessions also varied significantly, best shoot multiplication rate was obtained in PBL-4 and PBL-3 followed by PBL-2 and PBL-5. The per cent rooting in vitro derived shoots was maximum in PBL-4 and minimum in PBL-1. The present study will be helpful in selection of accessions/s for both ex situ and in situ conservation strategies and also for mass propagation of this medicinal herb.

Estimation of genetic mechanism of stomatal traits influencing grain yield in hexaploid wheat (Triticum aestivum L.)

Efforts to improve wheat plant have been made at various plant characters. Yield component breeding and modification of the plant architecture offer possibilities to develop more efficient breeding systems for increased grain yield. A 6 × 6 diallel experiment was conducted to determine the genetic mechanism of stomatal traits influencing grain yield in hexaploid wheat. Graphical representation indicated the over-dominant type of gene action for 1000-seed weight, seed yield per plant, leaf venation, stomatal size, epidermal cell size and stomatal frequency suggesting that selection would be difficult in early segregating generation. Hence heterosis breeding may useful for genetic improvement for these traits. Non allelic interactions were found to be absent for all traits. The genotype Aas-11 contained maximum dominant genes for epidermal cell size while genotype 9515 for 1000grain weight and seed yield per plant. The genotype 9516 possessed maximum dominant genes for leaf venation. Whereas, genotype Iqbal-2000 carried maximum dominant genes for stomata size.

A new positive relationship between pCO2 and stomatal frequency in Quercus guyavifolia (Fagaceae): a potential proxy for palaeo-CO2 levels.

The inverse relationship between atmospheric CO2 partial pressure (pCO2) and stomatal frequency in many species of plants has been widely used to estimate palaeoatmospheric CO2 (palaeo-CO2) levels; however, the results obtained have been quite variable. This study attempts to find a potential new proxy for palaeo-CO2 levels by analysing stomatal frequency in Quercus guyavifolia (Q. guajavifolia, Fagaceae), an extant dominant species of sclerophyllous forests in the Himalayas with abundant fossil relatives. Stomatal frequency was analysed for extant samples of Q. guyavifolia collected from17 field sites at altitudes ranging between 2493 and 4497 m. Herbarium specimens collected between 1926 and 2011 were also examined. Correlations of pCO2-stomatal frequency were determined using samples from both sources, and these were then applied to Q. preguyavaefolia fossils in order to estimate palaeo-CO2 concentrations for two late-Pliocene floras in south-western China. In contrast to the negative correlations detected for most other species that have been studied, a positive correlation between pCO2 and stomatal frequency was determined in Q. guyavifolia sampled from both extant field collections and historical herbarium specimens. Palaeo-CO2 concentrations were estimated to be approx. 180-240 ppm in the late Pliocene, which is consistent with most other previous estimates. A new positive relationship between pCO2 and stomatal frequency in Q. guyavifolia is presented, which can be applied to the fossils closely related to this species that are widely distributed in the late-Cenozoic strata in order to estimate palaeo-CO2 concentrations. The results show that it is valid to use a positive relationship to estimate palaeo-CO2 concentrations, and the study adds to the variety of stomatal density/index relationships that available for estimating pCO2. The physiological mechanisms underlying this positive response are unclear, however, and require further research.

Effect of Culture Conditions on Stomatal Density and Stomatal Index in Four Cactus Species

Abstract: We evaluated type of stomata, as well as differences in stomatal frequency in three areas of the plant (apical, middle and basal) under two culture conditions (in vitro and ex vitro), in four cactus species (Opuntia ficus-indica, Hylocereus undatus, Escontria chiotilla and Mammillaria petterssonii). We measured stomatal density (SD) and the stomata index (SI) for both factors, plant area and culture condition. Stomata typology were cyclocytic, tetracytic or opuntioid type in O. ficus-indica and parallelocytic type in E. chiotilla, H. undatus and M. petterssonii. It was observed that SD was higher ex vitro than in vitro in H. undatus and M. petterssonii, but the opposite was true for O. ficus-indica and E. chiotilla. The apical region had the highest SD both in in vitro and ex vitro, and the interaction between culture condition and explant areas was highly significant, implying that the impact of culture type is different for each distinct stem area.

Comparative Micro-morphological and Karyomorphological Studies in Three Mulberry Varieties (<i>Morus</i> spp.)

This article reveals the micro-morphology and karyomorphological characters of three mulberry varieties, namely, Thysong, S-41 and Morris multicaulis. Stomatal frequency, somatic chromosome number, ploidy level and karyotype analysis were studied for these varieties. Thysong is diploid with 2n=28, S-41 is triploid with 2n=42 and Mortis multicaulis is uneuploid with 2n=30 regarding somatic chromosomes numbers. The somatic chromosome length ranges from 1.26 to 2.83 mu m, whereas the arm ratio ranges from 0.48 to 1.00 mu m. Stomatal frequency is smaller in triploid varieties when compared to diploid and uneuploid mulberry varieties. In all the three varieties three to four types of chromosomes have been observed. Chromosomes are small sized with a narrow range of variation in length.

Response of leaf water status, stomatal characteristics, photosynthesis and yield in black gram and green gram genotypes to soil water deficit.

Drought is one of the most important abiotic stresses constraining crop productivity worldwide. The objective of the present study was to investigate the differences in drought tolerance at leaf and stomatal level of black gram (genotypes: T9, KU 301, PU 19, USJD 113) and green gram (genotypes: Pratap, SG 21-5, SGC 16, TMB 37). Drought was applied for fifteen consecutive days at flowering stage (35 days after sowing). Mid-day leaf water potential (ΨL), leaf area, photosynthesis rate (PN), leaf chlorophyll, stomatal conductance (gs) and seed yield of drought- treated plants were calculated relative to those of well watered plants. Stomatal characteristics were observed in terms of stomatal frequency (SF) and stomatal aperture size (SA). Among the studied genotypes, T9 (black gram) and Pratap (green gram) proved their better tolerance capacity to drought by maintaining higher leaf area, ΨL, PN, leaf chlorophyll, gs and SA which contributed to better seed yield. Between the two crops, green gram appeared to be affected to a greater extent, as it experienced higher reduction in yield than black gram. A highly significant positive correlation (level 0.01) of seed yield was obtained with leaf area, ΨL, PN, leaf chlorophyll, gs and SA, whereas SF was found to be poorly correlated with seed yield.

Morpho-criteria and karyotype studies in three mulberry varieties

Morpho-criteria, karyotype analysis, chromosome number and ploidy levels were studied for three mulberry varieties. Mysore local and RFS-175 is diploid with 2n=28 and BC2-59 is triploid with 2n=42 somatic chromosomes numbers respectively. Somatic chromosome length ranges from 1.29 m to 3.29 m where as arm ratio ranges from 0.59 to 1.00 m. Karyotypes of these taxa are symmetric. Only metacentric and submetacentric chromosomes are found in the somatic complement. Stomatal frequency is lesser in triploid variety when compared to diploid varieties.

A study of the nature and magnitude of inter-relationship among components of economic worth in Saffron (Croccus sativusL.)

Fifty clones of saff ron (Crocus sativus L.) were planted in a randomized bock design wi th three repl ications at Saffron Research Station, Pampore, SKUAST-Kashmir during 2010. Observations were recorded on 10 randomly selected and tagged competitive plants for 11 morphological, physiological, floral and corm attributes. The estimates of genotypic correlation coeff icients were higher in magnitude through simi lar in direction for al l the trai ts. The results have further revealed that the number of flowers corm−1 exhibited a strong signif icant positive association with all the traits. The fresh pistil weight, an important yield attributing character revealed a strong positive association with all the f loral attributes except number of radical leaves plant−1 and number of flowers corm−1. Similarly, stomatal frequency also recorded signif icant positive association with all the trai ts. The average weight of daughter corms showed signi f icant posi tive association with stomatal size and positive association wi th chlorophyll content. The average weight of daughter corms shows signi f icant positive association with stomatal size and positive association with chlorophyll content. A signif icant positive association of average weight of daughter corms with number of daughter corms was observed both at phenotypic and genotypic levels, indicating that an increase in number of daughter corms results in proportional decline in average corm weight. Identif ication of f ive elite genotypes with distinct superiority in yield and corm attributes could be a source for further improvement and development of high yielding varieties.

Analysis of genetic traits for drought tolerance in maize.

Fifty-four genotypes of maize were crossed and evaluated in the field during the crop season in February 2012 under both normal and water stress conditions. To identify the major parameters responsible for variation among genotypes, single linkage cluster analysis and principle component analysis (PCA) were carried out. Thirteen characters were studied. The PCA showed that the first six components, with eigen values >1, contributed 82.30% of the variability among the genotypes under normal field irrigation conditions while other PCs (7-13) had eigen values less than 1. Under drought conditions, the first four PCs, with eigen values >1, contributed 64.79% of the variability among genotypes while the other PCs (5-13) had eigen values less than 1. In the absence of water stress, heritability ranged from 68% (sucrose content) to 99% (plant height) and genetic advance ranged between 158.43% for stomatal frequency and 0.87 for biological yield. Under drought conditions, the coefficient of variability (CV) was 1.43-7.79, whereas estimates of heritability ranged between 68% and 99% for sucrose content and leaf area, respectively. The values of genetic advance ranged between 153.41 for stomatal frequency and 0.47 for nitrogen content. CV was 1.52-7.38 under drought conditions. The results indicated that the plant characters studied were under the control of additive genetic effects and suggested that selection should lead to fast genetic improvements. Clusters with superior agronomic types were identified and could be exploited for the transfer of desirable genes to improve the yield potential of the maize crop.

Physiological and anatomical variations in three rice (Oryza sativaL.) genotypes for transport and emission of methane

Plant-mediated transport is the major pathway of methane (CH4) emission from wetland paddy fields. The present experiment was conducted to understand the mechanism of CH4 transport through rice paddies. A field measurement of CH4 emission was done with three rice genotypes Ranjit, Piolee and Swarna Mahsuri to identify plant physiological and anatomical characteristics influencing gas emission, which could provide insight to the mechanism of CH4 transport. CH4 emission estimation by a closed chamber technique revealed significant variations in emission of CH4 among the varieties. Variety Ranjit was identified as a low emitting variety compared to the others. The leaf area index, tiller number, leaf and root dry weight were closely associated with CH4 emission. The rate of leaf transpiration, stomatal conductance, leaf stomatal frequency and size of the xylem vessels were identified to be strong determinants of CH4 emission suggesting a transport pathway of CH4 along with the transpirational xylem water flow and subsequently through open stomata of leaf blade. Low emitting variety Ranjit exhibited superior yield and yield attributing characteristics in terms of panicle dry weight and high density grain (%) highlighting the role of source–sink carbohydrate partitioning in regulating CH4 emissions. Cultivation of low emitting varieties with higher grain productivity can be an effective environmentally-friendly biological mitigation strategy for CH4 emission from rice paddies.