Phenological and physiological responses to drought stress and subsequent rehydration cycles in two raspberry cultivars

AbstractRaspberry (Rubus idaeus L.) is a deciduous plant with perennial roots, 75% of which are concentrated in the upper level of the soil. Its shallow rooting system requires a regular water supply; a water deficit can affect fructification as well as cane growth and yield for the following season. Despite the demonstrated drought stress impact on the raspberry, there is little information about the phenological and physiological responses to drought stress. The main goal of this study was to evaluate the effects of drought stress on the phenological phases, physiological parameters and yield of two raspberry cultivars: Heritage (remontant type) and Meeker (non-remontant type). All plants were grown in pots under greenhouse conditions, and the following watering treatments were applied: (T1) well-watered, 100% irrigation and (T2) a controlled drought-stress cycle. The volumetric soil water content (θ), phenological phases, leaf net photosynthetic rate (A), transpiration rate (T), and stomatal conductance (gs) were registered periodically. The free proline and total soluble sugars were also determined. Based on the phenological study, Heritage under drought-stress (T2) showed earlier flowering and a shorter fruit production period in relation to well-watered plants (T1). In Meeker, T2 extended the cane and summer lateral elongation, showing earlier senescence. Leaf gas exchange decreased with drought stress, A declined after 28-day period under drought stress, from 9.2μmolCO2m−2s−1 to 3.0μmolCO2m−2s−1 in Heritage, and from 12.2μmolCO2m−2s−1 to 3.0μmolCO2m−2s−1 in Meeker. In both cultivars, the free proline and total soluble sugars increased with drought stress. The fruit production was also affected in the next season under T2 condition, decreasing in 34 and 38% in relation to well-watered plants

Jet shapes in ep collisions at HERA

New measurements of the jet shape in ep collisions at HERA using the k_T-cluster jet algorithm are presented.Comment: 7 pages, 3 figures; plenary talk given at the 3rd UK Phenomenology Workshop on HERA Physics, Durham, UK, September 199

La "máquina" o "generador" de terremotos en un laboratorio universitario

La máquina o generador de terremotos es un dispositivo experimental que trata de modelizar el comportamiento de una falla. En la actividad propuesta, se le muestra al alumnado la complejidad de ciertos sistemas, así como la dificultad de predecir su comportamiento. Aunque inicialmente se postuló como un experimento abierto dirigido a estudiantes de enseñanza secundaria y bachillerato, la calidad de los datos que pueden obtenerse permite que pueda plantearse como un experimento en unlaboratorio universitario de ciencias de la Tierra. Los datos obtenidos en una experiencia de este tipo pueden ser equiparables, en cierto sentido, a los datos obtenidos por redes sísmicas regionales, en especial, los datos referentes a la sismicidad generada por una falla o sistema de fallas, en términos de magnitud, tiempo y caída de esfuerzos. Eso sí, con la clara ventaja de que en pocos minutos puede reproducirse lo que serían cientos o miles de años de acción de las fuerzas tectónicas. En función del nivel del curso en el que se proponga dicha experiencia, planteándose en este caso como una experiencia cerrada centrada en la obtención de determinados resultados, se pueden utilizar diferentes análisis de datos, fundamentalmente de tipo estadístico. Estos análisis permitirán conocer el nivel de predictibilidad de un modelo de estas características. Este trabajo plantea diferentes métodos y analiza los resultados que pueden obtenerse con este modelo mecánic

Topological Measure Locating the Effective Crossover between Segregation and Integration in a Modular Network

We introduce an easily computable topological measure which locates the effective crossover between segregation and integration in a modular network. Segregation corresponds to the degree of network modularity, while integration is expressed in terms of the algebraic connectivity of an associated hyper-graph. The rigorous treatment of the simplified case of cliques of equal size that are gradually rewired until they become completely merged, allows us to show that this topological crossover can be made to coincide with a dynamical crossover from cluster to global synchronization of a system of coupled phase oscillators. The dynamical crossover is signaled by a peak in the product of the measures of intra-cluster and global synchronization, which we propose as a dynamical measure of complexity. This quantity is much easier to compute than the entropy (of the average frequencies of the oscillators), and displays a behavior which closely mimics that of the dynamical complexity index based on the latter. The proposed toplogical measure simultaneously provides information on the dynamical behavior, sheds light on the interplay between modularity vs total integration and shows how this affects the capability of the network to perform both local and distributed dynamical tasks

The Effect of Nitrogen Fertilisation on the Morphological Development and Growth Rate of Star Grass (\u3cem\u3eCynodon nlemfuensis\u3c/em\u3e)

Nitrogen is one of the main inputs used in forage production systems to increase productivity. However, in Cuba, the availability of fertiliser N is limited and therefore if applied, needs to be used with high efficiency. Previous studies (Johnson, 2001, Del Pozo, 2003) investigated the effects of N on growth, carbohydrate and protein content but did not consider morphological changes in Cynodon nlemfuensis. A study was therefore undertaken investigating how N application influences morphological development of the plant and how these changes might affect the efficiency of use of applied N

The energy-constrained quickest path problem

This paper addresses a variant of the quickest path problem in which each arc has an additional parameter associated to it representing the energy consumed during the transmission along the arc while each node is endowed with a limited power to transmit messages. The aim of the energy-constrained quickest path problem is to obtain a quickest path whose nodes are able to support the transmission of a message of a known size. After introducing the problem and proving the main theoretical results, a polynomial algorithm is proposed to solve the problem based on computing shortest paths in a sequence of subnetworks of the original network. In the second part of the paper, the bi-objective variant of this problem is considered in which the objectives are the transmission time and the total energy used. An exact algorithm is proposed to find a complete set of efficient paths. The computational experiments carried out show the performance of both algorithms