ORIGINAL ARTICLE

Effect of storage time of Albizia lebbeck (L.) Benth. seeds on the germinative capacity

Efecto del tiempo de almacenaje de las semillas de Albizia lebbeck (L.) Benth. en la capacidad germinativa

Marlen Navarro,^I G. Febles,^II Verena Torres,^II R.S. Herrera,^II Aida Noda,^II

ABSTRACT

In order to evaluate the storage effect of A. lebbeck seeds on the viability, germination and dormancy indicators, a completely randomized design with factorial arrangement (3 x 6) was used, in which the factors were determined by the study years and storage times. A variance analysis was performed, according to simple classification model in factorial arrangement. The multiple comparison Duncan test (1955) was applied and differences were declared as significant at P <0.05. The percentage of viable seeds slightly decreased, as the storage increased. The most marked decrease occurred in the range of 0 to 2 months of storage started (mss) for three years, with significant differences between both evaluations in each year. Germination had variable performance in each year. In each storage period, the highest percentage, although without differ each other, it was found at 0 mss. In each of the months there were no significant differences between years, except for the value reported at 7 mss for years 1 and 3.The first year (31.0%) was not different from year 2 (34.0%), and in turn the latter showed no differences with regard  to year 3 (37.75%). At the start of storage (0 mss), the values of dormant and hard seeds were identical (52.85%), although, from this evaluation slight differences were observed, which only at 11 mss were 7% (51.0 vs 58.0% respectively). It is very probably that the germination percentage and longevity of A. lebbeck seeds depend on the time they spent in the store, indicating that the intrinsic factors may be the main responsible agent of viability loss.

Key words: Albizia lebbeck, germination, viability, dormancy.

RESUMEN

Para evaluar el efecto del almacenamiento de las semillas de A. lebbeck en los indicadores viabilidad, germinación y dormancia, se utilizó un diseño completamente aleatorizado con arreglo factorial (3 x 6), en el que los factores estuvieron determinados por los años de estudio y los tiempos de almacenamiento. Se realizó análisis de varianza, según modelo de clasificación simple en arreglo factorial. Se aplicó la dócima de comparación múltiple de Duncan (1955) y las diferencias se declararon  como significativas en valores de P < 0.05. El porcentaje de semillas viables disminuyó ligeramente, en la medida que aumentó el almacenaje. El descenso más marcado se presentó en el intervalo de 0 a 2 meses de iniciado el almacenamiento (mdia) para los tres años, con diferencias significativas entre ambas evaluaciones en cada año. La germinación tuvo comportamiento variable en cada año. En cada período de almacenamiento, el porcentaje más alto, aunque sin diferir entre sí, se constató a 0 mdia. En cada uno de los meses no se encontraron diferencias significativas entre los años, a excepción del valor informado a los 7 mdia para los años 1 y 3. El año 1 (31.0 %) no difirió del 2 (34.0 %), y a su vez este último no mostró diferencias con respecto al 3 (37.75 %). Al inicio del almacenamiento (0 mdia), los valores de semillas dormantes y duras fueron idénticos (52.85 %), aunque, a partir de esta evaluación se observaron ligeras diferencias, que solo a 11 mdia fueron de 7 % (51.0 vs 58.0 %, respectivamente). Es muy probable que el porcentaje de germinación y la longevidad de las semillas de A. lebbeck dependan del tiempo que permanecen en el almacén, lo que indica que los factores intrínsecos pueden constituir el principal agente causante de la pérdida de viabilidad.

Palabras clave: Albizia lebbeck, germinación, viabilidad, dormancia.

INTRODUCTION

The study of viability preserving by storing is one of the starting points of researches related with seeds performance, in which is expected to determine whether this procedure may influence on the detection of dormancy in tree legume species in a relatively short time. The papers on this subject also have among their objectives to determine whether that the mentioned procedure contributes to the knowledge of some characteristics of dormancy, viability and germination.

Albizia lebbeck (L.) Benth. is one of the tropical tree species that has been identified in Cuba as promising for current production systems, which involves plants and animals in an agro-ecological context (Paretas and Lopez 2006).

The objective of this research was to evaluate the storage effect of A. lebbeck seeds on uncontrolled environmental conditions, specifically with respect to viability and germination indicators. It also intends, to know through this process some dormancy characteristics.

MATERIALS AND METHODS

Experimental design and treatments. The dormancy presence was studied by the variables germination and viability of A. lebbeck seeds at regular intervals (evaluations) during eleven months in a sufficiently ventilated place, similar to conventional warehouses of enterprises, farms and seed banks in Cuba, described by Yanez and Funes (1989) and Funes et al. (1998). The temperature and mean relative humidity were recorded during the three years of study and are shown in figure 1.

A completely randomized design for germination and viability, with factorial arrangement (3 x 6) was used, in which the factors were determined by the study years (3) and storage times, per months (6).

Studied variables

Viable seeds. Living seeds, with capacity for germination under non limiting conditions of temperature, water, oxygen and light.

Germinated seeds. Germination was interpreted as the capacity of the embryo main structures to begin growth in visual terms and the emergency of the embryo radicle.

Hard seeds .Viable seeds which not germinate when the standard germination test end in each evaluation, due to the covers impermeability.

Dormant seeds. Viable seeds which are not able to germinate because of some dormatic obstacle in them (hard seeds), so when the germination test ends they were subjected to the seminal covers removal. This procedure consists on to cut the testa with a scalpel. The result was offered seven days after the test started in the cabin and it was named dormant seeds percentage. 

Experimental procedure. To make a fast estimate of seeds viability the tetrazolium (TZ) topographical test was used. For this test an aqueous solution of chloride of 2, 3, 5-triphenyl tetrazolium (pH 6.5-7.5), at 1.0% concentration was used. Random samples from a fraction of A. lebbeck seeds were taken and four replications were established, 100 seeds each. These ones were placed to absorb, with previous removal of seminal covers in the aqueous solution mentioned before. For the evaluation of viability, calculation and the results expression, the international rules which control the work in this biochemical test for tree legumes and others species (AOSA 2013) were considered, that are based on the coloration or not of the embryo structures. The results were expressed in viable seeds percentage.   

To do the germination test capsules Petri, with 184 g of river sand (washed and disinfected) as inert substrate were used. At the sowing moment, 48mL of distilled water (at room temperature) were applied, measure that was fitted to the value of the sand saturation capacity. In each evaluation, the capsules stayed in the cabin under approximately controlled conditions of light (12h), temperature (25 ºC) and humidity (85 % HR) during 21d, which coincides with the ruled by the ISTA (2004) for the seeds of tropical shrubs and trees. The evaluation carried out to 0 mss represents the beginning of the storage period.

Statistical processing of results. To assess the performance of temperature and mean relative humidity in the warehouse during the three experimental years an interval of 10 years was established, in which the three experiments were included. To this information an analysis known as determination of the confidence interval (CI) was carried out, in this case for 95% of probability. The data show that the performance of mean temperature and mean relative humidity during the research years was included within the CI.

Variance analyses were performed, according to simple classification model in factorial arrangement (3 x 6) for germination and viability variables. The data were transformed according to aresin √x+0.375. The multiple comparison of Duncan (1955) test was used and differences were declared significant at P <0.05 values. The statistical processing was performed by using the program InfoStat. version 1.0 (Di Rienzo et al. 2001).

RESULTS AND DISCUSSION

At the beginning of the research, the humidity content of the seeds was between 10 and 12%. According to Carvalho and Nakagawa (2012), these values tend to equilibrate with the environment as time passes, mainly when storage is not hermetic. Therefore, it was extremely important to know the deterioration degree that could present the A. lebbeck seeds before starting the storage period (Delouche 2005), so the topographical tetrazolium test was performed.

The results of this test showed that the seeds began their life in the store with 99.25; 100 and 100% of viability for the first, second and third year of study, respectively (figure 2), indicating that the deterioration was practically nonexistent. This agree with that informed by Rosental et al. (2014), who explained that the deterioration is reflected in the viability, only when the seeds are moving towards an advanced stage, due to that they are able to repair the damage only when this one does not become irreversible. In addition, the high percentage of viability of albizia seeds when storage start (0 mss) suggested that there were not negative factors, environmental or management, during harvesting and processing process before storage.

Longevity and deterioration. Significant differences between evaluations for interaction harvesting year per seeds storage time were found. In figure 2 are represented the percentage values of viability of A. lebbeck seeds on the six evaluations carried out during the three experimental years. The curves show the similarity of the results for the storage years; it could say that all follow the same tendency. The most marked decrease occurred in the range of 0 to 2 mss for the three years, with significant differences between both evaluations in each year.

The percentage of A. lebbeck viable seeds slightly decreases as storage time increased. The natural aging of these seeds was a slow, gradual and natural process. These results agree with Bruggink et al. (1999) and Bhanuprakash and Umesha (2015) with regard to the tendency that viability experiment during storage. These authors state that this performance is not linear in time, but usually follows a sigmoid pattern and depends on the species.

This is a logical process, as it is known that, even under ideal storage conditions can only be maintained the viability, but never improve it (Carvalho and Nakagawa, 2012).

The performance may be associated to different intrinsic factors. Among them, according to Priestley (1986) and Smith and Berjak (1995), are the breakdown of cell membranes, the loss of catalytic activity of enzymes, the accumulation of mutations in chromosomes and reserves food decrease, elements that were not measured in this experiment, and that may have exhibited some extent.

In other tree species from Leguminosae family, whose freshly harvested seeds, as A. lebbeck, they presented orthodox performance, storage under ambient conditions not significantly limits viability. Timyan (1996), Powell (1997), González et al. (1998) and CATIE (2000) also reached similar conclusions in studies with other trees from the tropic.

Germination capacity. Figure 3 shows the interaction between the studied factors and indicates the occurrence of a similar performance pattern for the three years throughout the experimental period.

Germination had a variable performance in each year. In each storage period, the highest percentage, although not differ from each other, it was observed at 0 mss. Then, declined to 7 mss, except in the third year, that instead of continuing to decline up to 7 mss increased between 7 and 9 mss. However, statistically there were not found significant differences between both evaluations.

In each of the months (individually) significant differences between the years in which germination was evaluated were not found, except in the value informed at 7 mss, for the first and third years. In this case, the first year (31.0%) did not differ from the second (34.0%). In turn, the latter showed no difference with the third (37.75%).

Mathias (1998), when measuring the germination of A. lebbeck seeds at three, six and twelve months of stored under ambient conditions, also found a similar performance. Same habit noted González et al. (1998) in the seeds of L. leucocephala cv. Cunningham under similar storage conditions.

Similar results were informed in Acacia farnesiana (L.) Willd. (Timyan 1996), when the germination percentage of fresh seeds ranged between 10 and 40 %. Another example is Albizia guachapele (Kundh) Dugand., whose seeds without receiving previous treatment show 20 to 35% of germination (CATIE 2000) and Pithecellobium dulce (Roxb.) Benth., with values between 36 and 54% for young seeds ( Molina et al. 1996).

The recorded percentages were always lower than the value obtained at the start of the evaluation period of each year (0 mss) and up to 2 mss, without statistically differ.

Another element that should be discuss are Harrington (1972) criteria, supported by Baskin and Baskin (2014), regarding the influence of temperature and humidity content in the storage. During uncontrolled storage, the respiration rate is one of the problems associated to the viability loss. A high respiration rate can lead to a rapid loss of energy and food reserves, especially in the embryo that is not able to germinate. In turn, the respiration rate increases with the increase of ambient temperature and the humidity content of seeds, among other factors. The information of figure 1 shows that during the experiment the temperature fluctuated as the relative humidity.

Period and intensity of dormancy. Regardless of the explained interactions, a general appreciation of the information indicates that the high expression for viability and germination indicators was presented at the beginning of the study, while the viability percentages in each evaluation were always higher than those of the standard germination test (figure 2 and figure 3). Even, in the last evaluation (11 mss), there was a marked difference between the two indicators. The viable seeds did not germinate when there were provided the conditions that favor the germination process, according to Cohn (2006).

This phenomenon may be associated to what in the plants physiology is known as dormancy (Hilhorst et al. 2010). According to Kigel et al. (2015), a large group of tropical species from Leguminosae family show dormancy in their seeds.

Dormancy in legumes is due to the cover impermeability (Jayasuriya et al. 2012 and Venier et al. 2012). In this experiment, the germination test determined the presence of the named "hard seeds" (figure 4).

When analyzing the percentage of dormant seeds and their physical expression, as hard seeds in each of the evaluations, at the start of storage (0 mss) the values were identical (52.85 %), although from this evaluation slight differences were observed, which only at 11 mss were of 7 % (51.0 vs 58.0 %, respectively). Each value represents the average of the three years. This also supports the view that there is a direct link between dormant seeds and hard seeds, and state that the dormancy in this species is closely related to the seeds hardness.

At the end of the germination tests, in each year, and as more objective verification element between dormancy / hard seed relation, a small cut was applied to seeds and they remained germinating for seven additional days. The results showed germination values close to 100%.

According to Hilhorst et al. (2010) and Nonogaki (2014), there are several dormancy degrees, which can range from very slight to very severe (deep). When evaluating the experimental data obtained up to this point, it can be inferred that there is a dormancy of approximately 50 %, which does not decrease noticeably during one year.

It is concluded that the seed storage during a year was a useful method, by which it was determined the dormancy existence and the performance of viability, germination and emergence.

The results of this experiment allow stating that during postharvest management, prior to storage starting, the A. lebbeck seeds were not perceptibly deteriorate; while when the storage time increase they aging at a progressive rate.

It is very probably that the germination percentage and longevity of A. lebbeck seeds depend on the time they spent in the warehouse, indicating that the intrinsic factors may be the main responsible agent of viability loss.

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Marlen Navarro, Estación Experimental de Pastos y Forrajes “Indio Hatuey”. Universidad de Matanzas. Central , España Republicana. CP 44280. Matanzas, Cuba. Email: boulandier@ihatuey.cu