Histochemistry and morphoanatomy study on guava fruit during ripening

Abstract

Guava (Psidium guajava L.) is a highly perishable fruit due to its intense metabolism during ripening. Information on the enzyme activities that degrade pectic substances, as well as the amount of pectin, is very contradictory and not clearly defined. Thus, this study aimed to monitor the changes occurred in the fruit during ripening through histochemical, physical, and scanning microscopy processes. Guavas were picked at the half-mature stage and stored for 9 days at 22 ± 1 °C and 78 ± 1% RH. The analyses conducted on the day of harvest (0) and each day of storage (1, 2, 3, 4, 5, 6, 7, and 8 days) were: firmness and histochemical analyses (ferric chloride, lugol, comassie blue, vanillin hydrochloric, and ruthenium red) observed under an optic microscope and a scanning electron microscope. Ruthenium red showed a high amount of pectin in the cell wall on day zero as well as its decrease in the wall during ripening and its accumulation in the central area of the cell. Scanning microscopy showed loss of the cell structure during ripening. Those observations suggest that the pectin is the main polymer responsible for firmness maintenance in the guava fruit.

Mechanism of firmness loss in guava cv. Pedro Sato during ripening at room temperature

“…The results of this study are similar to those reported by Botelho et al (2016) and Abreu et al (2012a), who reported a reduction of 70 and 73%, respectively, in the firmness of guava cv. Pedro Sato, during four days of storage at room temperature.…”

“…Pectin polymers are considered primarily responsible for the firmness of green fruits (Abreu et al, 2012a) and their degradation is one of the most notable events during ripening and softening of the fruit. In guavas, it is not different.…”

“…However, the content of pectins described in the literature for guava pulp (about 2.5% fresh weight and 15% dry weight) (Xisto et al, 2004;Linhares et al, 2007) is very small to be considered the main responsible for the maintenance of firmness. According to Abreu et al (2012a), throughout the ripening of guava cv. Pedro Sato, pectin from the cell wall gradually migrates into the cell, probably in vacuoles, and the function of this migration is still unexplained.…”

“…However, according to Linhares et al (2007) is not found or it is very low the activity of PG, making the information about the activity of these enzymes contradictory, and the mechanisms that control ripening not clearly defined. Thus, the knowledge of changes occurring during this process is important to clarify and establish scientific bases which enable the development of new post-harvest technologies, increasing, therefore, the shelf life of these fruits (Abreu et al, 2012a).…”

Produção, rendimento e caracterização físico-química de pectina a partir da entrecasca de melancia (Citrullus lanatus): otimização por experimento Box-Behnken

“…Outros açúcares neutros, como galactose e arabinose podem ser observados em cadeias laterais (FERNNDES et al, 2014). Vários são os usos da pectina, nos frutos os polímeros de pectina são os responsáveis por manter a firmeza dos frutos verde e maduros (SPILLER et al, 2018;ABREU et al, 2012), e nos processos industriais como por exemplo, pode ser utilizada na produção de minibactérias, na fabricação de gomas e balas de mascar, geleias, biofilmes e espessantes para sucos (LIMA et al, 2017;DA SILVA et al, 2014).…”