Physiological, biochemical, and ultrastructural aspects of Coffea arabica L. seeds under different cryopreservation protocols

Abstract

Cryopreservation is a technique that may potentially conserve the germplasm of species of the Coffea genus for an indeterminate time. The aim of this study was to evaluate the physiological, biochemical and ultrastructural characteristics of cryopreserved seeds of Coffea arabica L., cultivar Catucaí amarelo IAC 62, which was subjected to different protocols regarding dehydration, precooling, cooling, rewarming and cathode water use. According to each protocol, the seeds were subjected to fast or slow drying to moisture contents of 17 or 20% (wet basis), cooled in different ways, and then immersed in liquid nitrogen for 24 hours. Different rewarming times in a water bath were also used. Physiological, biochemical and ultrastructural analyses were performed on the seeds after the cryopreservation steps. Moisture content at a 17% wb is the key factor for the cryopreservation of Coffea arabica L. seeds, which have better physiological quality and better preserved cell structures. Precooling of coffee seeds before immersion in liquid nitrogen does not provide advantages compared to direct immersion. The rewarming times tested (2, 4, and 6 minutes) and cathode water use did not cause changes in the physiological and biochemical quality or in the cell structures of Coffea arabica L. cryopreserved seeds. The pattern of cell structure observed in all seeds indicates that the damage from cryopreservation is less drastic in the cells of the embryos than in those of the endosperm, with the latter less tolerant to the stresses of dehydration, precooling, and rewarming.

Trolox equivalent antioxidant capacity of Coffea arabica L. seeds

“…Catalase expression was affected by the different seed water contents (Figure 6A). This result was also reported by Figueiredo et al (2021), who found higher catalase activity in coffee seeds dried up to 17%, which maintained their initial high physiological quality after immersion in liquid nitrogen. In the present study, in seeds from fruits harvested at the greenish-yellow and cherry stages, there was an increase in catalase activity as the water content decreased, regardless of storage (Figure 6 A1 and A2).…”

“…Regarding the enzymatic profiles studied before and after storage of the coffee seeds, variations in the intensity of the isoforms were observed as a function of the different water contents and maturation stages (Figure 6). In coffee seeds, enzymatic profiles are commonly used to complement quality evaluations under different stress situations, especially in seeds with different water contents (Brandão Júnior;Vieira;Hilhorst, 2002;Coelho et al, 2015;Rosa;Fernandes, 2017;Abreu et al, 2018;Coelho et al, 2019;Figueiredo et al, 2021). It is evident in the isoenzymatic profiles of catalase, esterase and malate dehydrogenase that there was a greater band intensity for seeds with water contents below 30% at both maturation stages.…”

“…In the present study, in seeds from fruits harvested at the greenish-yellow and cherry stages, there was an increase in catalase activity as the water content decreased, regardless of storage (Figure 6 A1 and A2). Catalase has been widely investigated in studies on coffee seeds as an indicator of physiological quality, but the results differ in relation to the seed water content studied and their physiological performance (Santos et al, 2014;Coelho et al, 2015;Coelho, Rosa;Fernandes, 2017;Figueiredo et al, 2021).…”

“…Coffee seed quality is assessed through official germination and tetrazolium tests (Brasil, 2009) however, such assessments can be complemented by biochemical tests that evaluate enzymatic systems. The evaluation of the activity of enzymes involved in some metabolic pathways can aid in interpreting physiological results and in elucidating which processes are involved in desiccation and storage tolerance (Coelho et al, 2015;Rosa;Fernandes, 2017;Abreu et al, 2018;Coelho et al, 2019;Figueiredo et al, 2021).…”

Disentangling the effects of liquid nitrogen on impermeable seed coated species

“…Seeds of Nelumbo nucifera were exposed to alternating wet and dry heat by immersing them in boiling water for 5 minutes followed by drying in an incubator at 40°C for 24 hours, a process that was repeated ten times (Gama-Arachchige et al, 2013).At intervals of every 3rd, 7th, and 10th day, 100 seeds were sampled for moisture content analysis in triplicates of 15 seeds each. Additionally, for the imbibition test, 3 replicates of 15 seeds were collected, and 10 seeds were reserved for scanning electron microscopy in zip bags.…”