Background: Common bean (Phaseolus vulgaris L.) grain filling is vulnerable to drought and heat stress. The objective of the study was to evaluate the effect of humidity restriction, high night temperatures and their combination in common bean.Methods: The plants were grown in pots at maximum field capacity (100% FC) until the grain filling began. Afterwards, maintained until harvest at: 1) 100% FC, 2) 50% FC at ambient day/night temperature (AT), 22.58°C/16.94°C, 3) 100% FC with high night temperature (HNT) 21.47°C and 4) 50% FC with HNT (combined stress). Evaluations included phenotypic assessment using red-green-blue color segmentation in: green (healthy), yellow (senescence) and brown (necrotic). Result: The combined stress in the cv. Rosa Bufa significantly and synchronously accelerated leaves and pods senescence. In contrast, in leaves of cv. OTI, the loss of green color began several days earlier than in pods. The effect of HNT and combined stress depends on common bean cultivar.
En 2014 se cultivaron en invernadero dos formas de frijol común (Phaseolus vulgaris L.), una silvestre y otra domesticada, ambas de hábito de crecimiento indeterminado tipo IV, trepador. El cultivo se realizó en hidroponía permitiendo la máxima expresión de su potencial genético. La forma silvestre y la domesticada de P. vulgaris son importante reservorio de genes para el fitomejoramiento. El objetivo fue realizar una comparación mutua de caracteres fenológicos, morfológicos y de los componentes del rendimiento, así como de algunas variables fisiológicas como duración del área foliar, tasa de asimilación neta, índice de llenado de la vaina e índice de cosecha. La forma silvestre presenta un ciclo de cultivo más largo que la domesticada y un mayor número de vainas desde la etapa de llenado de la vaina hasta la de madurez de cosecha y en esta última un mayor número de semillas por planta, aunque las semillas de un menor tamaño y peso individual; asimismo, el porcentaje de germinación fue similar en ambas formas sin necesidad de escarificar la semilla. En la forma silvestre, la producción total de materia seca por planta y la duración del área foliar son mayores, esta última característica debido a que su follaje permanece funcional más tiempo en comparación con la domesticada. La tasa de asimilación neta es mayor en la domesticada, lo cual indica su precocidad. El índice de cosecha tradicional y modificado (incluyendo y excluyendo la raíz en ambos casos) es mayor en la forma domesticada debido a la selección bajo domesticación.
El conocimiento de las temperaturas cardinales y velocidad de germinación pueden ser útiles como criterio para la determinación de fechas y localidades de siembra de una especie dada. Dichas variables (temperatura y velocidad) se han determinado para cierto número de especies cultivadas. Sin embargo, no se encontró esta información para los cultivares de tomate de cáscara (Physalis philadelphica Lam.), no obstante que dicha especie ocupa el cuarto lugar en importancia entre las hortalizas cultivadas en México. El objetivo del presente trabajo fue determinar las temperaturas cardinales y las velocidades de germinación de las semillas de los cultivares Diamante, Chapingo, Tecozautla y Cerro Gordo de tomate de cáscara. Se descartó la presencia de latencia en estos cultivares. El presente estudio se realizó en el Colegio de Postgraduados y en la Universidad Autónoma Chapingo en 2011-2012. En cámaras de germinación se pusieron a germinar semillas sobre papel filtro en cajas Petri en oscuridad y temperatura constante de 3, 5, 7, 9, 10, 15, 20, 25, 30, 35, 40 y 45 oC, el diseño experimental fue un completamente al azar con arreglo factorial con cinco repeticiones por cultivar. Se contaron y descartaron cada cinco días las semillas germinadas (radícula emergida) durante 25 días. Las temperaturas cardinales de germinación para los cultivares Diamante, Chapingo, Tecozautla y Cerro Gordo fueron: mínima: 7-9, 9, 7, 10 oC; óptima: 25-30, 30, 30, 25-30 oC respectivamente; máxima: 45 °C para todos los cultivares. Las mayores velocidades de germinación fueron: 23.4, 23.6, 21.8 y 18.7 semillas por día, respectivamente.
The common bean (Phaseolus vulgaris L.) pod wall is essential for seed formation and to protect seeds. To address the effect of water restriction on sugar metabolism in fruits differing in sink strength under light–dark cycles, we used plants of cv. OTI at 100% field capacity (FC) and at 50% FC over 10 days at the beginning of pod filling. Water restriction intensified the symptoms of leaf senescence. However, pods maintained a green color for several days longer than leaves did. In addition, the functionality of pods of the same raceme was anatomically demonstrated, and no differences were observed between water regimes. The glucose and starch concentrations were lower than those of sucrose, independent of pod wall size. Remarkably, the fructose concentration decreased only under water restriction. The cell wall invertase activity was twofold higher in the walls of small pods than in those of large ones in both water regimes; similar differences were not evident for cytosolic or vacuolar invertase. Using bioinformatics tools, six sequences of invertase genes were identified in the P. vulgaris genome. The PvINVCW4 protein sequence contains substitutions for conserved residues in the sucrose-binding site, while qPCR showed that transcript levels were induced in the walls of small pods under stress. The findings support a promising strategy for addressing sink strength under water restriction.
Background: Seed mass is a key component of adaptation in plants that are strongly affected by development and maturity, and, at the same time, all is modulated by the environment of cultivation. Hypotheses: The response to water deficit in seeds of P. vulgaris L. and P. acutifolius A. Gray is species-dependent and affects their biochemical and morphological characteristics. Studied species: The studied cultivars were Rosa Bufa (P. vulgaris) and cv. 10017 (P. acutifolius). Seeds were obtained from plants grown at 100 % and 25 % soil field capacity during their pod development. Study site and dates: The experiments were performed during May and August 2018 in a greenhouse at the Colegio de Postgraduados, Texcoco, State of Mexico (altitude 2,353 m). Methods: The biochemical and morphological characteristics and the grain size of starch in seeds cotyledons were assessed. Results: Water restriction had no significant effects on the seed thickness, width, or mass only length decreased in P. acutifolius. In both species, the axis size of the starch granules decreased due to the stress, glucose concentration increased, sucrose and starch were not altered. Water imbibition increased six times in P. vulgaris seeds with no effect on the germination. The α-amylase activity was 25 - 35 % lower in both species due to the water restriction, particularly in P. acutifolius the activity was two-fold higher than in P. vulgaris. Conclusions: Comparing the carbohydrate concentration in germinating seeds of common and Tepary beans gave insights on the nutrient reserves mobilization during seed maturation and germination.
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