Physiological quality of castor seeds (Ricinus communis L.) after processing

Abstract

Castor bean seeds are the raw material used for extracting oil destined to pharmaceutical and industrial ends. The appropriate application of post-harvest technologies, such as processing, is required to ensure the production of top quality seeds. Thus, this study aimed at assessing the physiological quality of seeds from two castor bean genotypes, classified according to their specific mass and size. Castor seeds of the genotypes EVF102 and EVF103 were mechanically harvested and then classified with the aid of cylindrical sieves and a densimetric table. This procedure was conducted at the processing unit of the company Sementes Goiás LTDA [Goiás Seeds Co.]. Evaluations of seed physiological quality were carried out in the Seed Laboratory of Instituto Federal Goiano, following a completely randomized design. The testing was conducted in four replicates, in a 2 x 2 x 5 factorial scheme (two genotypes x two sizes x five specific masses). The following parameters were appraised: (a) mass of one thousand seeds; (b) germination; (c) germination speed index; (d) emergence test; (e) emergence speed index; (f) electrical conductivity; and (g) accelerated aging. Genotype EVF102 seeds sized 8 mm, as classified by the densimetric table, showed the highest physiological quality, considering the germination, germination speed index, and emergence. Seeds of the genotype EVF103, sorted by size, exhibited no difference in physiological quality.

Studies on the Germination and Emergence of Castor Seedlings

“…This study confirmed the previous attempts reported in the literature that sorting castor seeds by weight, size, or density results in a higher germination rate but slower germination [15,16,49]. Nevertheless, sorting castor seeds according to their morphological characteristics has only a limited effect on the time for germination, and this practice alone would not be enough to obtain the high standard of emergence uniformity for adequate crop initial establishment.…”

“…The optimal temperature for castor seed germination was found to be near 31 °C (Figure 3). It should be emphasized that most studies on castor seed germination follow the suggestion of standardized tests for quality purposes and incubate the seed at suboptimal temperatures-alternating 20/30 °C or in the range from 25 to 28 °C [3,8,[13][14][15]17,[38][39][40]. Although the procedures for quality assessment need to be standardized, experiments on castor seed germination searching for agronomical performance, vigor, or biological meaning could find better results if they adopt temperatures close to the optimal for this tropical plant species.…”

“…Castor seed germination is a complex physiological process that is influenced by many factors, including its genetic traits, physiological condition, and the environmental conditions [4,6,[9][10][11][12][13]. Many attempts have been made aiming to improve castor seed germination, such as caruncle removal, soaking in water, scarification, treatment with gibberellin, the selection of varieties with fast germination, harvesting by raceme order, and sorting the seeds according to size and density [3,4,[14][15][16].…”

“…This article reports a series of studies evaluating factors that were previously observed to influence the seed germination of castor and other plant species. The objective was to test the following hypotheses: (1) that castor seed germination is delayed because the castor seed coat is impermeable to water [17][18][19], (2) that the time for germination is influenced by temperature [20][21][22], (3) that the mechanical resistance of the seed coat is a mechanism to delay germination [23][24][25][26][27][28][29][30], (4) that the germination ability is influenced by the seed weight, volume, density, and seed coat thickness [7,15,16], (5) that castor seed germination is influenced by the hormone gibberellin [4,29], (6) that selection for fast germination changes the morphological characteristics of the seed in its descendants [7,31,32], and (7) that the time for germination can be reduced with a pre-germination treatment [3,17].…”

Physiological Quality of Processed, Reprocessed, and Stored Sorghum Seeds: Impact of a Densimetric Table

“…According to Silva et al (2017), the electrical conductivity test provides an assertive separation of the different seed vigor levels measured indirectly, in addition to determining the amount of leachate in the soaking solution. Data obtained by Drumond et al (2019) reinforce that the growing increase in electrical conductivity compromises the physiological seed quality and vigor, causing a disorder of membrane cells, leaving the seeds more susceptible to external damage. Treatments D and P3R2 were sent directly for disposal and the results shown in Table 3 reinforce the high values of electrical conductivity for these treatments.…”