Standardizing germination in crambe culture (Crambe abyssinica)

It is a plant that, until recently, was used only as forage. However, given its rusticity and high potential to produce around 26 to 38% of oil, surpassing even soybeans in this regard, it has become a crop also aimed at producing vegetable oil (Neves et al. 2007 ).

Its seeds are spherical in shape and are surrounded by an integumentary structure called pericarp. In May 2009, an experimental planting was carried out in the southern region of Goiás, where a high unevenness of seed germination was observed, indicating supposed dormancy.

In general, three minimum conditions are necessary for seeds to germinate: they are mature, they are viable and they do not present dormancy (Carvalho & Nakagawa, 2000). The numbness provided by the integument is the most common and is characterized by the fact that, in most cases, it is impermeable to water. In this case, removing this structure can accelerate the germination process (Santarém 1995).

In this way, professors from the Federal Institute of Education Science and Technology Goiano – Morrinhos Campus carried out tests with C. abyssinica seeds in order to evaluate the percentage of imbibition and germination of these seeds in order to provide information on the best cultural practices.

The experiment was carried out at the Federal Institute of Education, Science and Technology Goiano – Campus Morrinhos. Evaluations were carried out on the percentage of imbibition and germination of seeds of C. abyssinica cultivar MS Brilhante, with and without pericarp. The seeds were obtained from Fundação de Mato Grosso do Sul, 2008 harvest. All tests were carried out with seeds initially containing 12% water on a wet basis.

In evaluating the percentage of imbibition, two lots of 100 seeds each were selected. In one of the lots, seeds with intact pericarp, without mechanical damage, were selected. Another batch underwent a mechanical scarification process in order to remove all the pericarp that surrounded the seed.

The seeds were placed in plastic cups containing 0,2 L of water. Seeds were weighed after the following periods of residence in water: 0 (dry mass), 2, 4, 6, 8 and 10 hours. When weighing, the seeds were removed from the water, filtered with a strainer and placed on paper towels to remove excess moisture. They were then weighed on a scale with an accuracy of 0,001 g. After weighing, the seeds were returned to the same water as at the beginning of the soaking period.

The masses obtained in each period of imbibition were verified in order to establish an equation to determine the time necessary for the seeds to reach approximately constant weight. Furthermore, the water mass gain of the seeds after two hours of residence in water was determined using Equation 1.

To determine germination, two batches of 50 seeds were selected, one batch with intact pericarp and the other batch without pericarp. The seeds were placed between two sheets of common white paper towel and placed in plastic containers measuring approximately 15 cm in diameter. The containers were placed on laboratory benches and moistened with a quantity of water equivalent to 2,5 times the weight of the substrate. The tests were carried out under alternating temperatures of 19 to 27°C and relative humidity of 55 to 70%.

Seven days after the start of the experiment, the top sheet of paper was removed from the seed sample and the seeds that had germinated were counted. Seeds that had emitted a radicle of at least two millimeters in length were considered germinated.

The results showed that the presence of the pericarp significantly affects the water gain by the seeds. Seeds of C. abyssinica, without the pericarp, reach an approximately constant mass about four hours after the start of the imbibition period. For seeds with pericarp, this level would possibly only be reached after more than 10 hours after the start of imbibition (Figure 01). This way, it possibly takes about another two and a half hours to absorb the total amount of water necessary to trigger the physiological processes of germination.

The average percentage variation in seed mass gain reduced with increasing imbibition time (Table 01).

There was no difference in the percentage of mass gains in the first two hours of soaking, which were 53,45% and 56,09% for seeds with pericarp and without pericarp, respectively. After six hours, the seeds without pericarp practically achieved constant gains. The seeds with pericarp continued to gain mass, indicating that they are permeable and, supposedly, do not present integumentary dormancy. It is believed that a greater number of weighings could demonstrate the time needed for these seeds to reach constant mass.

Despite being permeable, the presence of the pericarp appears to delay the physiological processes that trigger germination. This fact could be confirmed in the evaluation of germination. The germination of C. abyssinica seeds, without pericarp, showed higher germination (90%) compared to seeds with pericarp (44%).

The test led to the conclusion that, although the pericarp of C. abyssinica seeds is permeable to water, its presence reduces the physiological processes of germination. Removing the pericarp provides an increase in seed germination of up to 90%, therefore being a recommended practice.

Prof. Dr. Renato A. Alves Ruas. Federal University of Viçosa – Rio Paranaíba Campus.

Prof. Dr. Geovane Barbosa do Nascimento. Federal Institute Goiano – Morrinhos Campus.

Prof. Dr. Erwing Paiva Bergamo. Federal Institute Goiano – Morrinhos Campus.

Student of the Technical Course in Agriculture Rouves H. Daur Júnior. Federal Institute Goiano – Morrinhos Campus.

Student of the Technical Course in Agriculture Ricardo Guimarães de Arruda. Federal Institute Goiano – Morrinhos Campus.

Check out this article, with photos, figures and equation, at the link below: