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The effects of plant hormones and sucrose (Suc) on potato (Solanum tuberosum L.) tuberization were studied using in vitro cultured single-node cuttings. Tuber-inducing (high Suc) and-noninducing (low Suc or high Suc plus gibberellin [GA]) media were tested. Tuberization frequencies, tuber widths, and stolon lengths were measured during successive stages of development. Endogenous GAs and abscisic acid (ABA) were identified and quantified by high-performance liquid chromatography and gas chromatography-mass spectrometry. Exogenous GA4/7 promoted stolon elongation and inhibited tuber formation, whereas exogenous ABA stimulated tuberization and reduced stolon length. Indoleacetic acid-containing media severely inhibited elongation of stolons and smaller sessile tubers were formed. Exogenous cytokinins did not affect stolon elongation and tuber formation. Endogenous GA1 level was high during stolon elongation and decreased when stolon tips started to swell under inducing conditions, whereas it remained high under noninducing conditions. GA1 levels were negatively correlated with Suc concentration in the medium. We conclude that GA1 is likely to be the active GA during tuber formation. Endogenous ABA levels decreased during stolon and tuber development, and ABA levels were similar under inducing and noninducing conditions. Our results indicate that GA is a dominant regulator in tuber formation: ABA stimulates tuberization by counteracting GA, and Suc regulates tuber formation by influencing GA levels

PWM DC-DC power converter technology underpins many energy conversion systems including renewable energy circuits, active power factor correctors, battery chargers, portable devices and LED drivers.  Following the success of Pulse-Width Modulated DC-DC Power Converters this second edition has been thoroughly revised and expanded to cover the latest challenges and advances in the field. Key features of 2nd edition:  * Four new chapters, detailing the latest advances in power conversion, focus on: small-signal model and dynamic characteristics of the buck converter in continuous conduction mode; voltage-mode control of buck converter; small-signal model and characteristics of the boost converter in the discontinuous conduction mode and electromagnetic compatibility EMC. * Provides readers with a solid understanding of the principles of operation, synthesis, analysis and design of PWM power converters and semiconductor power devices, including wide band-gap power devices (SiC and GaN). * Fully revised Solutions for all end-of-chapter problems available to instructors via the book companion website. * Step-by-step derivation of closed-form design equations with illustrations. * Fully revised figures based on real data.  With improved end-of-chapter summaries of key concepts, review questions, problems and answers, biographies and case studies, this is an essential textbook for graduate and senior undergraduate students in electrical engineering. Its superior readability and clarity of explanations also makes it a key reference for practicing engineers and research scientists. 

The vascular cambium produces secondary xylem and phloem in plants and is responsible for wood formation in forest trees. In this study we used a microscale mass-spectrometry technique coupled with cryosectioning to visualize the radial concentration gradient of endogenous indole-3-acetic acid (IAA) across the cambial meristem and the differentiating derivatives in Scots pine (Pinus sylvestris L.) trees that had different rates of cambial growth. This approach allowed us to investigate the relationship between growth rate and the concentration of endogenous IAA in the dividing cells. We also tested the hypothesis that IAA is a positional signal in xylem development (C. Uggla, T. Moritz, G. Sandberg, B. Sundberg [1996] Proc Natl Acad Sci USA 93: 9282-9286). This idea postulates that the width of the radial concentration gradient of IAA regulates the radial number of dividing cells in the cambial meristem, which is an important component for determining cambial growth rate. The relationship between IAA concentration in the dividing cells and growth rate was poor, although the highest IAA concentration was observed in the fastest-growing cambia. The radial width of the IAA concentration gradient showed a strong correlation with cambial growth rate. The results indicate that IAA gives positional information in plants

Nearly forty years ago R. L. Berg proposed that plants with specialized pollination ecology evolve genetic and developmental systems that decouple floral morphology from phenotypic variation in vegetative traits. These species evolve separate floral and vegetative trait clusters, or as she termed them, \"correlation pleiades.\" The predictions of this hypothesis have been generally supported, but only a small sample of temperate-zone herb and grass species has been tested. To further evaluate this hypothesis, especially its applicability to plants of other growth forms, we examined the patterns of phenotypic variation and covariation of floral and vegetative traits in nine species of Neotropical plants. We recognized seven specific predictions of Berg's hypothesis. Our results supported some predictions but not others. Species with specialized pollination systems usually had floral traits decoupled (weak correlation; Canna and Eichornia) or buffered (relationship with shallow proportional slope; Calathea and Canna) from variation in vegetative traits. However, the same trend was also observed in three species with unspecialized pollination systems (Echinodorus, Muntingia, and Wedelia). One species with unspecialized pollination (Croton) and one wind-pollinated species (Cyperus) showed no decoupling or buffering, as predicted. While species with specialized pollination usually showed lower coefficients of variation for floral traits than vegetative traits (as predicted), the same was also true of species with unspecialized or wind pollination (unlike our prediction). Species with specialized pollination showed less variation in floral traits than did species with unspecialized or wind pollination, as predicted. However, the same was true of the corresponding vegetative traits, which was unexpected. Also in contrast to our prediction, plants with specialized pollination systems did not exhibit tighter phenotypic integration of floral characters than did species with generalized pollination systems. We conclude that the patterns of morphological integration among floral traits and between floral and vegetative traits tend to be species specific, not easily predicted from pollination ecology, and generally more complicated than R. L. Berg envisaged.

Introduction. Leaf area is often related to plant growth, development, physiology and yield. Many non-destructive models have been proposed for leaf area estimation of several plant genotypes, demonstrating that leaf length, leaf width and leaf area are closely correlated. Thus, the objective of our study was to develop a reliable model for leaf area estimation from linear measurements of leaf dimensions for citrus genotypes. Materials and methods. Leaves of citrus genotypes were harvested, and their dimensions (length, width and area) were measured. Values of leaf area were regressed against length, width, the square of length, the square of width and the product (length × width). The most accurate equations, either linear or second-order polynomial, were regressed again with a new data set; then the most reliable equation was defined. Results and discussion. The first analysis showed that the variables length, width and the square of length gave better results in second-order polynomial equations, while the linear equations were more suitable and accurate when the width and the product (length × width) were used. When these equations were regressed with the new data set, the coefficient of determination (R2) and the agreement index ‘d’ were higher for the one that used the variable product (length × width), while the Mean Absolute Percentage Error was lower. Conclusion. The product of the simple leaf dimensions (length × width) can provide a reliable and simple non-destructive model for leaf area estimation across citrus genotypes. Introduction. La surface foliaire est souvent liée à la croissance, le développement, la physiologie et le rendement des plantes. Beaucoup de modèles non destructifs ont été proposés pour estimer la surface foliaire de plusieurs génotypes végétaux ; ils ont montré que la longueur et la largeur des feuilles, de même que la surface foliaire, étaient étroitement corrélées. L'objectif de notre étude a donc été de développer un modèle fiable pour estimer la surface foliaire à partir de mesures linéaires des dimensions de feuilles pour les génotypes d'agrumes. Matériel et méthodes. Les feuilles de certains génotypes d'agrumes ont été récoltées et leurs dimensions (longueur, largeur et surface) ont été mesurées. La surface foliaire a été corrélée à la longueur, la largeur, le carré de la longueur, le carré de la largeur et le produit (longueur × largeur). Les équations les plus précises, qu’elles soient linéaires ou polynomiales de second ordre, ont été testées à nouveau avec un nouvel ensemble de données, puis l'équation la plus fiable a été définie. Résultats et discussion. La première analyse a montré que les variables longueur, largeur et carré de la longueur donnaient de meilleurs résultats dans les équations polynomiales de second ordre, tandis que les équations linéaires étaient plus appropriées et précises lorsque la largeur et le produit (longueur × largeur) étaient utilisés. Lorsque ces équations ont été utilisées avec le nouvel ensemble de données, le coefficient de détermination (R2) et l'indice « d » ont été les plus élevés dans le cas de l’équation utilisant le produit (longueur × largeur) comme variable, tandis que le pourcentage moyen d'erreur absolue était alors le plus faible. Conclusion. Le produit (longueur × largeur) des simples dimensions de la feuille peut fournir un modèle non-destructif fiable et facile pour estimer la surface foliaire des génotypes d'agrumes. Introducción. La superficie foliar a menudo está ligada al crecimiento, al desarrollo, a la fisiología, así como al rendimiento de las plantas. Ya se propusieron sendos modelos no destructivos para estimar la superficie foliar de varios genotipos vegetales. Éstos mostraron que la longitud y la anchura de las hojas, así como la superficie foliar, estaban estrechamente relacionadas. Por ello, el objetivo de nuestro estudio fue el desarrollo de un modelo fiable para estimar la superficie foliar a partir de medidas lineares de las dimensiones de las hojas para los genotipos de cítricos. Material y métodos. Se cosecharon las hojas de ciertos genotipos de cítricos, y se midieron sus dimensiones (longitud, anchura y superficie). La superficie foliar se relacionó en cuanto a la longitud, a la anchura, al cuadrado de la longitud, el cuadrado de la anchura, y al producto (longitud por anchura). Las ecuaciones más precisas, que fueran lineares o polinómicas de segundo orden, se sometieron nuevamente a prueba con un nuevo conjunto de datos. Por último, se definió la ecuación más fiable. Resultados y discusión. El primer análisis mostró que las variables de longitud, anchura y cuadrado de la longitud ofrecían mejores resultados en las ecuaciones polinómicas de segundo orden. Sin embargo las ecuaciones lineares eran más apropiadas y precisas cuando se empleaba la anchura y el producto (longitud por anchura). Cuando dichas ecuaciones se emplearon con el nuevo conjunto de datos, tanto el coeficiente de determinación (R2) como el índice «d» fueron más elevados, en el caso de la ecuación que empleaba el producto (longitud por anchura) como variable. Sin embargo entonces el porcentaje medio de error absoluto era el más débil. Conclusión. El producto (longitud por anchura) de las simples dimensiones de la hoja puede proporcionar un modelo no destructivo, fiable y fácil para la estimación de la superficie foliar de los genotipos de cítricos.

In social insects, colony-level complexity may emerge from simple individual-level behaviors and interactions. Emergent global properties such as colony size, which can be viewed as a consequence of life history traits, may influence individual-level behaviors themselves. The effects of colony size on productivity, body size, behavioral flexibility, and colony organization are examined here by considering colony size as an independent variable. Large colony size commonly corresponds with complex colony-level performance, small body size, and lower per capita productivity. Analyzing the construction behavior of various wasp societies reveals that complexity of individual behavior is inversely related to colony size. Parallel processing by specialists in large colonies provides flexible and efficient colony-level functioning. On the other hand, individual behavioral flexibility of jack-of-all trades workers ensures success of the small and early societies.

This study presents results on the performance of apricot genotypes in Central Serbia. The research included observation and recording of biological (i.e. phenological) traits and in situ sampling of fruits from 1,210 grafted trees for determination of pomological and sensorial traits. A total of 14 genotypes were selected and compared with Hungarian Best (control cultivar). The difference in blossoming time between two years was one month. In 2006, blossoming time was found to be earlier in three genotypes, simultaneous in five and later in six genotypes as compared to the control. In 2007, bloom was earlier in four genotypes, simultaneous in four and later in six genotypes. Average fruit weight ranged from 41.34+/-0.8 to 81.50+/-4.1 g, T-5 being the only genotype having the fruit weight lower than Hungarian Best (49.07+/-2.2 g). The content of soluble solids, total sugars, and mineral matter ranged from 15.72-18.88%, 11.53-4.99%, and 0.29-0.43%, respectively, and total acidity was 0.77-1.08%. The appearance and the skin colour of the genotypes were highly attractive. They have promising traits which suggest that they can be useful parents in apricot breeding programmes.

The variations in physical properties such as the size dimensions, unit mass, sphericity, projected area, bulk density, true density, volume, coefficient of friction on various surfaces, and terminal velocity of shelled and kernel walnuts as a function of the moisture content were determined. With an increase in the moisture content, the sphericity, projected area, bulk density, volume, and porosity of shelled and kernel walnuts increased, whereas the true density linearly decreased. Studies on rewetted walnuts showed that the terminal velocity increased from 14.17 m/s to 15.50 m/s and from 12.60 m/s to 14.35 m/s for shelled and kernel walnuts, respectively. The static and dynamic coefficients of friction of shelled and kernel walnuts on chipboard and plywood surfaces also increased linearly with the increase in the moisture content.

Endogenous brassinosteroids (BRs) in the dwarf mutants Ika and Ikb of garden pea (Pisum sativum L.) and comparable wild-type plants were quantified by gas chromatography-selected ion monitoring using deuterated internal standards. In young shoots of the Ikb mutant, the levels of brassinolide, castasterone, and 6-deoxocastasterone were 23-, 22-, and 9-fold lower, respectively, than those of wild-type plants. Applications of brassinolide, castasterone, typhasterol, 3-dehydroteasterone, and teasterone normalized internode growth of Ikb seedlings. These findings indicate that the Ikb plants are Bit-deficient mutants, probably as a consequence of a block in the BR biosynthetic pathway prior to the production of teasterone. Young shoots of Ika plants contained only 50% less brassinolide and 5 times more castasterone than the equivalent wild-type tissues. The Ika seedlings were approximately 100 times less responsive to brassinolide than the Ikb mutant, and application of castasterone had only a marginal effect on Ika internode growth, suggesting that the Ika lesion results in impaired sensitivity to BR

We investigated rumen papillae morphology and the localization and expression of the Na+/K+-ATPase in eight sheep fed hay ad libitum (h) or hay ad libitum plus additional concentrate (h/c). Four sheep were provided with the ad libitum h-diet for 3 weeks. The second group of four sheep received the h-diet for only one week and was fed the mixed hay/concentrate (h/c) diet for another two weeks. The amount of concentrate supplement was stepwise increased from 150 to 1,000 g/day and given in two meals. Following slaughter rumen papillae from the atrium ruminis (AR), the rumen ventralis (RV) and the ventral blind sac (BSV) were fixed and examined for morphological changes and Na+/K+-ATPase localization by morphometric methods and immunohistochemistry. Ruminal epithelial cells (REC) originating from the strata basale to granulosum were also isolated. Cellular Na+/K+-ATPase expression (mRNA and protein) and differentiation state were determined by RT-PCR, Western blot, and flow cytometry. Compared with data from h-fed sheep, morphometric analysis revealed an increased length and width of rumen papillae in h/c-fed sheep, resulting in a marked 41% and 62% increase in rumen papillae surface in AR and RV, respectively. The rumen mucosa of h/c-fed sheep was characterized by a predominant stratum corneum (42+/-0.7 microm vs. 28+/-0.5 microm), but the thickness of the metabolically active cell layers remained unchanged. REC suspensions from h/c sheep generally contained more cells (7.30+/-0.83 vs. 3.49+/-0.52 x 107/mL; P less than 0.001) and an increased proportion of REC positive for basal cytokeratin and for the differentiation marker cytokeratin 10 (P less than 0.05). Cellular (cell membrane) and epithelial (stratum basale to stratum granulosum) Na+/K+-ATPase localization was similar between rumen regions and was not changed by concentrate feeding. After two weeks on the h/c-diet, a 96% increase in the absolute number of Na+/K+-ATPase-positive REC (P = 0.003) and a 61% elevation (P = 0.043) in Na+/K+-ATPase protein expression in REC from the upper third of the suprabasal cell layers were found. Moreover, a two-fold (P = 0.001) elevation in cell membrane surface area accompanied by a significant reduction in specific Na+/K+-ATPase fluorescence per square cm of cell membrane surface area was observed after h/c-feeding. Na+/K+-ATPase alpha subunit mRNA expression was also significantly reduced in the h/c-compared with the h-group. Thus, the h/c-diet led to a rapid increase in REC number and total cell membrane surface area in metabolically active and resorptive cell layers and was accompanied by a reduction in Na+/K+-ATPase mRNA expression and abundance per cell membrane surface area.