RESEARCH WORK

Effect of storage under ambient conditions on seeds from Leucaena leucocephala cv. Cunningham subject to partial hydration

Yolanda González¹; J. Reino¹; J. A. Sánchez² y R. Machado¹

¹Estación Experimental de Pastos y Forrajes "Indio Hatuey" Central España Republicana, CP 44280, Matanzas, Cuba
E-mail: yolanda.gonzalez@indio.atenas.inf.cu
²Instituto de Ecología y Sistemática, Ciudad de La Habana, Cuba

ABSTRACT

The objective of the work was to study the effect of storage under ambient conditions on the germination of seeds from Leucaena leucocephala cv. Cunningham subject to partial hydration. The treatments were: control, no scarification (T0); thermal scarification (TS) with H2O at 80ºC, for two minutes (T1); TS plus partial hydration, on tray with tap water for 28 hours (T2); TS plus partial hydration, in jute sac moist with tap water for 28 hours (T3); TS plus partial hydration in tray with tap water and TMTD at 0,1% (pesticide) for 28 hours (T4); TS plus partial hydration, in jute sac moist with tap water and TMTD at 0,1% (pesticide) for 28 hours (T5). The hydrated seeds were dehydrated during 72 hours exposed to air and under shade, before being stored. Germination and viability were measured after 0, 1, 2, 3, 4, 6, 18, 30 and 42 months. A completely randomized design and four replications per treatment were used. There were significant differences (P<0,001) among treatments regarding germination and viability. The highest germination values were detected in T2 and T3 at all times, except after 18 and 30 months, when they were only higher in T3. After 42 months there was 0% germination in all treatments, while the control reached 9,3%. On the other hand, viability showed higher values in T0. It is concluded that the seeds that were subject to the combination of the treatment with partial hydration, before being stored under ambient conditions, remained reinvigorated for germination until 30 months.

Key words: seed storage, germination, hydration, Leucaena leucocephala cv. Cunningham.

INTRODUCTION

Leucaena leucocephala seeds show seed coats impermeable to water and gases (Buch, Jara, Franco 1997), which restrict their germination. To eliminate their effect, it is recommended to use among other treatments- water at 80ºC during two minutes (González and Mendoza, 2008). In addition, germination may be stimulated with the partial hydration technique. With this procedure satisfactory results have been achieved to condition, reinvigorate and harden seeds from vegetables and pioneer forest species (Sánchez, Calvo, Muñoz and Orta 1999; Brancalion, Novembre, Rodrigues and Tay 2008).

The partial hydration technique also proved to be effective in fresh seeds from L. leucocephala cv. Cunningham, combining thermal scarification and partial hydration in water treatments, which increased the heat tolerance of this cultivar and, thus, seedling establishment under full solar exposure (Reino, 2005). The best effects were obtained with the pregerminative treatment of thermal scarification (water at 80ºC during two minutes), combined with the partial hydration of seeds, two hours before the end of stage II (28 hours), and seed dehydration for 72 hours. When validating this treatment, González et al. (2005) obtained satisfactory results in the seeds from L. leucocephala cv. Cunningham. The objective of this study was to learn the effect of storage under ambient conditions on the germination of L. leucocephala seeds.

MATERIALS AND METHODS

The study was conducted with the seeds from the trial carried out by González et al. (2005). The partial hydration technique was applied on fresh seeds of L. leucocephala cv. Cunningham (T1, T2, T3, T4 and T5) and a control without any pregerminative treatment (T0) was also studied.

Design and treatments. A completely randomized design and four replications were used to study six treatments at each storage time; they were:

T0: Control (untreated).

T1: Thermal scarification (TS) with H2O at 80ºC, during two minutes.

T2: TS plus partial hydration, on tray with tap water for 28 hours, and dehydration during 72 hours exposed to air and under shade.

T3: TS plus partial hydration, in jute sac moist with tap water during 28 hours, and dehydration for 72 hours exposed to air and under shade.

T4: TS plus partial hydration, on tray with tap water and TMTD at 0,1% (pesticide) for 28 hours, and dehydration during 72 hours exposed to air and under shade.

T5: TS plus partial hydration, in jute sac moist with tap water and TMTD at 0,1% (pesticide) for 28 hours and dehydration during 72 hours exposed to air and under shade.

The partial hydration technique was applied to 0,5 kg of seeds per treatment, after thermal scarification (combination of treatments). Before applying hydration, they were placed in layers of up to two seeds in each case and, afterwards, they were dehydrated exposed to air and under shade during 72 hours, until they had the same size as the non hydrated ones. Each treatment was individually studied, during storage under ambient conditions, in paper bags (six-pound bags) after 0, 1, 2, 3, 4, 6, 18, 30 and 42 months.

Measurements. The germination and viability percentages and the rotten seeds were studied (ISTA, 1999).

Statistical analysis. The comparison between means was made through the multiple range test (Duncan, 1955). All the values in percentage were transformed according to sin-1Ö%.

RESULTS AND DISCUSSION

Table 1 shows the germination results during each storage time. There were significant differences (P<0,001) among treatments. The highest values were detected in T2 and T3 at all times, except after 18 and 30 months, when they were only higher in T3. After 42 months, germination was 0% in all pregerminative treatments, while the untreated control reached values of 9,3%.

These results are in correspondence with the report by González et al. (2005), who obtained the best reinvigorating effects with treatment T2, which showed higher emergence and growth.

It is important to state that several authors have reported the significant effect exerted by partial hydration treatments on seed reinvigoration and their positive influence on the increase of germination and other indicators of plant growth and development, as well as on their production (Sánchez, Hernández, Reino and Muñoz 2007); but no reference has been made to storage under ambient conditions of the hydrated seeds, important aspects which should be studied for the handling of remnant seeds when this technique is applied- and to learn until when they may be planted.

González, Hernández y Mendoza (1998) reported the performance of germination and viability in seeds from L. leucocephala cv. Cunningham, but applying the treatment at the moment of planting.

Scarification is an elemental technique to break hard seed dormancy, as proven by González and Mendoza (2008) and by González, Reino and Machado (2009a) in L. leucocephala. The results were positive when this procedure was combined with partial hydration (González et al., 2005; 2008; 2009b). In this study the beneficial effect on germination was observed until 30 months, although it was applied before storage.

Table 2 shows viability in each storage time. There were significant differences (P<0,001) among treatments; the highest values were found in T0, at all the studied times; although it did not differ from T3 at month 0, or from T2 and T3 in the first month. Seemingly, the highest deterioration in the hydrated seeds occurred when the storage period advanced, after the second month, which occurred more slowly in untreated seeds (control). In this case, deterioration could have been associated to natural ageing (Sacandé, 2000), as observed in the viability reached by this treatment after 42 months (25,9%).

Table 3 shows the values of rotten seeds. There were significant differences (P<0,01) among treatments; the lowest values were found in T0, at all times, which was motivated by the hardness of seed coats; this prevented (to a lower extent) seed deterioration, as compared with the treated ones with thermal scarification as well as with partial hydration-, which showed the highest values after 42 months (100%).

The higher the viability of the seed lot at the beginning of storage, the higher it will be maintained in a certain environment (Bruggink et al., 1999), and although seed deterioration can start in the field, it is influenced by handling since harvest or by natural deterioration (ageing), according to Sacandé (2000). This could lead to the complete loss of germination capacity (Black, Derek Bewley and Halmer 2006), especially when the storage conditions are not adequate (Muñoz et al., 2009). The higher values in T0 can be ascribed to the fact that the seeds were not handled and maintained dormancy because of seed coat hardness, which did not occur with the ones subject to thermal scarification (T1) and to the combination of treatments including partial hydration (T2, T3, T4 and T5); in them viability was equalized to germination, because the seeds that did not germinate, rotted (table 3). They also showed, in general, lower viability values than T0, but germination was higher. It must be stated that all treatments had 0% viability after 42 months, possibly due to the depletion of seed reserves (Black et al., 2006) which originated 100% of seed rot.

It is concluded that the seeds subject to the combination of treatments including partial hydration maintained the reinvigorating effect for germination, until 30 months of storage under ambient conditions.

During storage seed deterioration was observed: in the hydrated ones it occurred after the second month, which was visible in viability decrease and led to the loss of germination capacity after 42 months. In the control treatment (undisturbed seeds) deterioration was slower, which was associated to natural ageing.