Effect of Size Classification on Physical and Physiological Quality Aimed at Pelletizing Seeds of Eucalyptus Species

Abstract

The aim of this work was to verify the effect of size classification on the physical and physiological quality of Eucalyptus spp. seeds to optimize the selection for covering. The seeds were separated in sieves with six size classes: 850, 710, 600, 500, 425 µm, and a non-perforated bottom (< 425 µm). Were evaluated the sieve retention, purity, weight of a thousand seeds, germination, and first count of germination. Sieve classification is effective for the separation of materials according to the best physical and physiological qualities. E. grandis seeds from the 710 µm sieve, E. robusta from the 850 µm sieve, and E. urophylla from the 710 and 850 µm sieves can be selected for covering, as they present maximum physical and physiological quality. For the three species, the smallest materials, retained in the 500, 425, and bottom <425µm sieves, must be discarded due to low purity and germination potential.

Eucalyptus citriodora, E. phaeotricha and E. propinqua seeds subjected to classification by sieves

“…2). The greater germinative potential in relation to the larger seeds were also reported by Naidu and Jones (2010) in E. grandis seeds and by Jeromini et al (2021) in E. grandis, E. robusta, and E. urophylla seeds. For seeds of E. phaeotricha and E. propinqua, these smaller seeds could be transferred to another set of sieves, or to a gravitational table for possible density separation as described for other species (Melo et al, 2018, Jeromini et al, 2019.…”

“…The high purity in general in the larger sized seeds portions, may be related to the possibility of impurities passing through the sieves, since these impurities are mostly unfertilized ovules and have a smaller size than the seeds, favoring a higher concentration of them in the portion of smaller sized seeds (Martins et al, 2014, Affonso et al, 2018. This behavior was also reported for E. maculata, by Silva et al (1994), E. grandis, E. robusta, and E. urophylla seeds (Jeromini et al, 2021) Guaranteeing pure seeds is difficult using only a set of sieves to separate seeds of the same size, as occurred with the seed lot of E. propinqua, as it is possible to verify in small seed processing works. Therefore, the need to carry out more seed processing studies, to guarantee the obtaining of pure seeds for commercialization is required (Araújo et al, 2011, Caldeira et al, 2016, Melo et al, 2016, Melo et al, 2018, Bernardi et al, 2019.…”

“…In this case, the use of classification sieves in the processing of seeds of these species of eucalyptus could be adopted to obtain more uniform classes and to separate and dispose of impurities before commercialization. A study with E. grandis, E. robusta, and E. urophylla seeds, showed that the classification by size obtained larger and havier seeds and this seeds had the best vigor and germination rates (Jeromini et al, 2021). Thus, guaranteeing seed lots of better physical quality, as observed in seeds of grass-mombaça (Melo et al, 2018) and grass-marandú (Jeromini et al, 2019).…”

“…For species of the Eucalyptus genus, seed propagation is viable and adopted by small and medium nurseries for seedling production (Cetnarski Filho and Carvalho, 2009, Affonso et al, 2018, Jeromini et al, 2021. However, after harvest the eucalyptus species present lots of seeds with a high variation in terms of size, shape, mass, as well as a high percentage of impurities, especially unfertilized ovules (Nakagawa et al, 2001, Martins et al, 2014, Affonso et al, 2018, Jeromini et al, 2021.…”

“…Blake, E. saligna Sm and E. maculata Hook, seed germination speed is affected by seed size more than by other factors such as temperature, light and maturation (Aguiar et al, 1979;Aguiar and Mardegan, 1987;Silva et al, 1994;). As for E. grandis, Hill ex Maiden, the size of the seed influences the germination potential (Nakagawa et al, 2001;Jeromini et al, 2021) and the seedlings survival in a nursery (Naidu and Jones, 2010).…”