Função do cálcio na degradação da parede celular vegetal de frutos

Calcium is one of the most important intracellular system of plants, it remains in ionic form while inside the cell, acting on the secondary metabolism of all cells. It is an element that plays different roles in plant tissues, especially in protecting the cell walls and membranes and signaling in response to changing biotic and abiotic stress. The softening of the fruit during its ripening involves changes in cell wall polysaccharides. Calcium bridges between pectic acids, or between these and other polysaccharides hinder access and the action of pectinolytic enzymes produced by the fruit and cause softening, and those produced by fungi and bacteria that cause decay. Calcium in plant cell wall, to covalently bind to pectins, gives rise to calcium pectate, restricting the action of polygalacturonase and pectin, and thus slowing the softening of fruits. The application of calcium both in spray and in the fruit results in grave: the preservation of fruit firmness, reduction of respiration rate of respiration, reduced ethylene production, the lower activity of β-galactosidase, an increase of hemicellulose, pectins and calcium in the pulp . In fruits, the effect of calcium has received much attention, since the applications of this cation promotes the retardation of ripening and senescence, prolonging the life and shelf life.O cálcio é um dos elementos mais importantes no sistema intracelular de plantas, pois permanece na forma iônica quando dentro da célula, atuando no metabolismo secundário de todas as células. É um elemento que desempenha diferentes funções nos tecidos vegetais, notadamente na proteção das membranas e paredes celulares e na sinalização de resposta às condições de estresse biótico ou abióticos. O amaciamento de frutos durante o seu amadurecimento implica em modificações de polissacarídeos da parede celular. As pontes de cálcio entre os ácidos pécticos ou entre esses e outros polissacarídeos dificultam o acesso e a ação de enzimas pectolíticas produzidas pelo fruto e que causam amaciamento, e daquelas produzidas pelos fungos e bactérias que causam deterioração. O cálcio na parede celular vegetal, ao ligar-se covalentemente às pectinas, dá origem ao pectato de cálcio, restringindo a ação da pectinametilesterase e poligalacturonase, e, consequentemente, retardando o amaciamento de frutos. A aplicação de cálcio tanto em pulverização nos frutos quanto em cova resulta em: preservação da firmeza do fruto, redução da respiração da taxa respiratória, redução da produção de etileno, menor atividade da β-galactosidase, aumento de hemicelulose, pectinas e cálcio na polpa. Em frutos, o efeito do cálcio tem recebido muita atenção, visto que as aplicações deste cátion promovem o retardamento da maturação e da senescência, prolongando o período de vida útil e o tempo de prateleira

Morphological and molecular characterization of Umbu-Cajá tree in the northeast region of Brazil

The umbu-cajá (Spondias sp.) is a fruit specie native of the brazilian semiarid region with high potential for cultivation. The juicy pulp is used in the production of juices and nectars. The aim of this study was to characterize 18 individuals of umbu-cajá tree at three sites located in the Brazilian northeast municipalities of Mossoró/RN and Apodi/RN to identify individuals with superior attributes for fruit processing and/or in natura consumption The morphological, physical and physicochemical characterization of 20 fruits of each individuals were performed. Leaves of trees were used for molecular analyses with Inter Simple Sequence Repeats (ISSR) and Random Amplified Polymorphic DNA (RAPD) markers. It was possible to verify that there are phenotypic variability among the fruits of umbu-cajá trees.  The individuals of the same region were grouped in the same group. JZ5, JZ6 and MA6 individuals can be used for pulp processing, while JZ1, JZ2, JZ3 and JZ6 are adequate for in natura consumption. The molecular analyses showed polymorphism for the two molecular markers used. The ISSR marker generated the greatest polymorphism among the individuals. However, the RAPD marker made it possible to achieve a more consistent cluster, which is in agreement with the geographical distribution of these individuals. The use of morphological markers together with molecular markers constitutes an important tool for characterizing umbu-cajá individuals.   Keywords: genetic resources, ISSR, RAPD, Spondias sp