The coffee seeds are problematic for the physiologycal quality, featuring low speed of seedling emergence. In this sense, this work was developed with the objective of evaluating the effect of sodium hypochlorite in the removal of the parchment and in the emergence and seedlings development of conilon coffee in nursery conditions. Coffee seeds of the variety Victoria were used, which were harvested in the cherry stage and pulped by hand. Seeds were dried in an oven with forced ventilation until reaching moisture contents of 35%, 30% and 25% wet basis. Then, the seeds with parchment were soaked in a sodium hypochlorite solution with concentrations of 4%, 5%, 6% and 7% active chlorine for 3 and 6 hours. For each moisture content, two additional treatments were added consisting of seeds with parchment and seeds in which the structure was removed manually. The characteristics evaluated were: emergence speed index, total emergence, dry mass of the shoots and root system. Utilization of sodium hypochlorite promoted an acceleration in seedling emergence speed similar to the method for manual removal of the parchment when using concentrations of 4%, 5%, 6% and 7% for 3 hours, at all moisture contents.
World coffee production is distributed among many countries and the Brazil has always occupied a prominent position in this activity as a major world producer and exporter [
However, seeds of this species present slow and uneven germination, in the field conditions [
Presence of the endocarp, a thin, hard and leather-like hull, known as the parchment, is one of the causes for slow germination of coffee seeds. However, the real cause of inhibition of this structure is not known. According to [
Thus, the development of an efficient, practical and inexpensive technique that can remove the parchment would be of great benefit to growers and nursery operators. [
Work performed by [
Based on these facts, the objective of the present study was to evaluate combinations of sodium hypochlorite concentrations and immersion times on removing the parchment and in accelerating the emergence and development of conilon coffee plants in nursery conditions.
The experiments were performed used conilon coffee seeds, Victoria variety, obtained from fruits harvested in the cherry stage. For extraction of the seeds, the fruits were pulped manually. Then the seeds were dried in an oven with forced ventilation at 36˚C until reaching moisture contents of 35%, 30% and 25% wet basis.
To check the degradation of parchment, 250 seeds were imbibed with this structure in 125 mL of aqueous solution of sodium hypochlorite at concentrations of 4%, 5%, 6%, and 7% of active chlorine for periods of 3 and 6 hours. For this, the seeds were placed in germination boxes using the screens of these boxes for all seeds remained immersed in the solution. The germination boxes were capped and kept in a BOD chamber at a constant temperature of 25˚C in the dark, where they remained for the periods for each treatment [
After applying the different treatments, the seeds were taken to a greenhouse and planted directly in perforated polyethylene bags measuring 10 × 20 cm, containing the Plantmax substrate and placing one seed at a depth of 2 cm in each bag. The bags were then covered with a layer of dry grass clippings to maintain moisture in the substrate, to prevent that the impact of irrigation water remove the substrate from the seeds and hinder the development of weeds. Irrigation was performed daily.
Effects of the treatments were evaluated by the following characteristics:
Counting of emerged seedlings was carried out at five day intervals from emergence of the first seedling to development of the cotyledons. Was used for calculation the formula proposed by [
where:
ESI: emergence speed index;
E1, E2, En: number of seedlings in the first, second and nth evaluation;
N1, N2, Nn: number of elapsed days from sowing to first, second and nth evaluation.
The percentage of total seedling emergence was determined by counting the number of normal seedlings em- erged in the last assessment of the ESI.
Upon completing the emergence test, the seedlings were removed from the substrate, washed and the shoots and roots were separated and placed in paper bags for drying during 72 hours in an oven at 70˚C with forced air circulation. Weighing was performed on a precision scale before and after drying, where the results are expressed in milligrams per plant (mg∙plant−1).
A randomized block experimental design was adopted with four repetitions in a 3 × 4 × 2 + 6 factorial, i.e., three degrees of initial moisture content, four concentrations of sodium hypochlorite, two immersion times and six additional treatments (intact seeds with parchment and seeds in which the parchment was removed manually for each moisture content). The experimental data were subjected to analysis of variance. For quantitative variables regression analysis was performed. For each moisture content, the treatments obtained from the combinations of sodium hypochlorite concentrations and pre-soaking times were compared to additional treatments applying the Tukey test at 5% probability, since the comparison of joint and other additional treatments.
Because there was no significant difference between the different moisture contents for additional treatments at levels of 1% and 5% probability, in all additional trials for all characteristics evaluated the mean of the observed variables was used in the three initial moisture contents.
Considering the period of exposure of coffee seeds in a solution of sodium hypochlorite for 3 hours, there was no significant difference for the rate of speed of seedling emergence in all degrees of moisture and concentrations tested, thus, using the average this variable (Figures 1(A)-1(C)).
At 6 hours, for all humidities, there was a decrease in the speed index seedling emergence as the concentration of sodium hypochlorite increased (Figures 1(A)-1(C)). It is noted that in the treatment with 35% humidity and concentration of 7%, this ratio was zero, which can also be seen from
In
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Analyzing the exposure time of the seeds in the sodium hypochlorite solution for 6 hours, it was observed that the concentration of 4% was the only treatment which showed satisfactory results for all moisture contents. Furthermore, when considering the period of 6 hours it is noticed that higher concentrations (6% and 7%) for all
Emergence speed index of conilon coffee seedling from seeds with moisture content of 35% (A); 30% (B) and 25% (C), after treatment with sodium hypochlorite at concentrations of 4%, 5%, 6% and 7% for periods of 3 and 6 hours
. Emergence speed index of conilon coffee seedlings after treatment with sodium hypochlorite at the concentrations of 4%, 5%, 6% and 7% for periods of 3 and 6 hours
Concentration | Time | Initial moisture content of the seeds (% w.b.) | |||||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
(%) | (h) | 25 | 30 | 35 | |||||||||||||
4 | 3 | 0.68 | b | c | 0.89 | a | 0.84 | a | |||||||||
6 | 0.76 | a | b | 0.81 | a | b | 0.70 | a | b | ||||||||
5 | 3 | 0.87 | a | b | 0.92 | a | 0.92 | a | |||||||||
6 | 0.65 | b | c | 0.57 | b | c | 0.39 | c | |||||||||
6 | 3 | 0.95 | a | 0.94 | a | 0.88 | a | ||||||||||
6 | 0.25 | e | 0.18 | d | 0.24 | c | d | ||||||||||
7 | 3 | 0.85 | a | b | 0.98 | a | 0.87 | a | |||||||||
6 | 0.17 | e | 0.15 | d | 0.00 | d | |||||||||||
Seed without parchment (manual removal) | 0.87 | a | b | 0.87 | a | 0.87 | a | ||||||||||
Seeds with parchment | 0.48 | c | d | 0.48 | c | 0.48 | b | c | |||||||||
CV (%) | 16.75 |
Averages followed by the same letter in the column do not differ at the level of 5% probability by the Tukey test.
moisture contents reduced the emergence speed of the plants, possibly due to damage to the embryo tissues of the seeds since sodium hypochlorite is a strong oxidant [
When comparing the seeds whose parchment was removed manually with those remaining with this structure, it is apparent that the removal promoted higher ESI. These results corroborate with those of [
It is observed by the regressions, which in the period of exposure of the seeds in a solution of sodium hypochlorite for 3 hours, the total seedling emergence coffee increased to concentrations of 5.1% and 6.5% for moisture of 35% and 25%, respectively, and thereafter decreased with increasing concentrations (Figures 2(A)-(C)). These values were obtained for the first of the regression equations derived 2nd degree. In seedlings from seeds with initial moisture of 30%, there was no significant difference for total emergence (
In a 6 hours period, in all moisture evaluated, seedling emergence of coffee decreased with increasing concentrations of sodium hypochlorite.
In
In
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Seeds whose parchment was manually removed reached emergence percentages greater than 90% for all
Total emergence of conilon coffee seedling from seeds with moisture content of 35% (A); 30% (B) and 25% (C), after treatment with sodium hypochlorite at concentrations of 4%, 5%, 6% and 7% by at 3 and 6 hours
. Total emergence of conilon coffee plants (%) after treatment with sodium hypochlorite at the concentrations of 4%, 5%, 6% and 7% for periods of 3 and 6 hours
Concentration | Time | Initial moisture content of the seeds (% w.b.) | ||||||||||||
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
(%) | (h) | 25 | 30 | 35 | ||||||||||
4 | 3 | 75.0 | a | 96.9 | a | b | 90.6 | a | b | |||||
6 | 78.1 | a | 81.3 | a | b | c | 78.1 | a | b | |||||
5 | 3 | 87.5 | a | 100.0 | a | 100.0 | a | |||||||
6 | 71.9 | a | 56.3 | c | 37.5 | c | ||||||||
6 | 3 | 93.8 | a | 90.6 | a | b | 90.6 | a | b | |||||
6 | 21.9 | b | 25.0 | d | 28.1 | c | ||||||||
7 | 3 | 93.8 | a | 93.8 | a | b | 84.4 | a | b | |||||
6 | 31.3 | b | 25.0 | d | 0.0 | d | ||||||||
Seed without parchment (manual removal) | 92.7 | a | 92.7 | a | b | 92.7 | a | b | ||||||
Seeds with parchment | 70.8 | a | 70.8 | b | c | 70.8 | b | |||||||
CV (%) | 16.25 |
Averages followed by the same letter in the column do not differ at the level of 5% probability by the Tukey test.
moisture contents. [
In the period of exposition in a solution of sodium hypochlorite for 3 hours, there was no significant effect of different concentrations for the dry mass of the aerial part of the variable coffee plantlets in all moisture contents (Figures 3(A)-(C)). This also occurred in seedlings from seeds with initial moisture content of 30% for 6 hours immersed in a solution of sodium hypochlorite (
In a 6 hours period, a reduction of the dry mass of the aerial part of seedlings of coffee as the concentration of sodium hypochlorite increased humidity of 35% (
The dry mass of the shoots of conilon coffee seedlings did not differ statistically between treatments when seeds presented 30% moisture content. In seedlings originated from seeds with 35% and 25% moisture, the treatment with 7% sodium hypochlorite for a period of 6 hours was the only treatment that caused a significant reduction of the dry mass of the shoots of seedlings in relation to the removal parchment manual, and there was no moisture in the first seedling emergence (
In a 3 hours period soaking seeds in a solution of sodium hypochlorite, dry root weight of seedlings of coffee was not significantly affected in moisture of 35% and 30% (
Analyzing 6 hours period, there was an increase in dry root weight of seedlings to 4.9% concentration of sodium hypochlorite in the moisture of 35%. From this value decreased slightly as the concentration increased. For other moisture, there was no significant effect of concentration for this variable.
Dry weight of the root system in coffee seedlings showed a similar behavior to the dry mass of shoots for the three humidities, i.e., at 30% moisture there was no difference between treatments and for 35% the same was observed, except for the concentration of 7% during 6 hours, since there was no emergence of seedlings. In seeds with 25% moisture content, the pre-germination treatment with sodium hypochlorite at a concentration of 7% for 6 hours was the only treatment with weight lower than that in which the parchment was removed manually (
Evaluation of the dry masses of the shoots and root systems indicate that the use of sodium hypochlorite not
Dry mass of the shoots of the conilon coffee seedling from seeds with moisture content of 35% (A); 30% (B) and 25% (C), after treatment with sodium hypochlorite at concentrations of 4%, 5%, 6% and 7% for periods of 3 to 6 h- ours
. Dry mass of the shoots of the conilon coffee seedling (mg∙plant−1) after treatment with sodium hypochlorite at the concentrations of 4%, 5%, 6% and 7% for periods of 3 and 6 hours
Concentration | Time | Initial moisture content of the seeds (% w.b.) | |||||||
---|---|---|---|---|---|---|---|---|---|
(%) | (h) | 25 | 30 | 35 | |||||
4 | 3 | 83.9 | a | b | 82.8 | a | 87.4 | a | |
6 | 69.5 | a | b | 72.5 | a | 84.7 | a | ||
5 | 3 | 86.2 | a | b | 89.4 | a | 87.0 | a | |
6 | 76.0 | a | b | 62.9 | a | 72.8 | a | ||
6 | 3 | 89.4 | a | b | 90.1 | a | 81.2 | a | |
6 | 61.8 | a | b | 72.8 | a | 48.9 | a | ||
7 | 3 | 90.6 | a | b | 94.7 | a | 80.5 | a | |
6 | 47.2 | b | 78.1 | a | 0.0 | b | |||
Seed without parchment (manual removal) | 91.5 | a | 91.5 | a | 91.5 | a | |||
Seeds with parchment | 73.5 | a | b | 73.5 | a | 73.5 | a | ||
CV (%) | 24.48 |
Averages followed by the same letter in the column do not differ at the level of 5% probability by the Tukey test.
. Dry mass of the root system of the conilon coffee seedling (mg∙plant−1) after treatment with sodium hypochlorite at the concentrations of 4%, 5%, 6% and 7% for periods of 3 and 6 hours
Concentration | Time | Initial moisture content of the seeds (% w.b.) | |||||||
---|---|---|---|---|---|---|---|---|---|
(%) | (h) | 25 | 30 | 35 | |||||
4 | 3 | 13.8 | a | b | 16.8 | a | 17.1 | a | b |
6 | 9.9 | a | b | 11.0 | a | 15.5 | a | b | |
5 | 3 | 20.6 | a | b | 21.2 | a | 20.9 | a | |
6 | 10.9 | a | b | 13.4 | a | 18.6 | a | ||
6 | 3 | 24.8 | a | 21.2 | a | 20.6 | a | ||
6 | 9.3 | a | b | 11.7 | a | 11.3 | a | b | |
7 | 3 | 18.4 | a | b | 26.9 | a | 19.1 | a | |
6 | 6.1 | b | 9.0 | a | 0.0 | b | |||
Seed without parchment (manual removal) | 24.7 | a | 21.7 | a | 21.7 | a | |||
Seeds with parchment | 10.1 | a | b | 10.1 | a | 10.1 | a | b | |
CV (%) | 47.26 |
Averages followed by the same letter in the column do not differ at the level of 5% probability by the Tukey test.
only resulted in good emergence, but did not affect proper development of conilon coffee seedlings.
The use of pre-germination treatments involving partial or total immersion of the seeds has grown significantly in order to improve performance [
Dry mass of the root system of the conilon coffee seedling from seeds with moisture content of 35% (A); 30% (B) and 25% (C), after treatment with sodium hypochlorite at concentrations of 4%, 5%, and 6%, 7% for periods of 3 and 6 hours
The use of sodium hypochlorite at concentrations of 4%, 5%, 6% and 7% for 3 hours, regardless of initial moisture content of the seeds, has a similar effect on manual removal of the parchment with regards to emergence percentage and speed for the coffee seedlings, and shoot and root dry mass.
The immersion of conilon coffee seeds in a 7% sodium hypochlorite solution for 6 hours reduced the emergency speed index and seedling development.
In general, the use of sodium hypochlorite in pre-germinating treatments of conilon coffee seeds shown a promising technique of low cost.
To the UENF for the scholarship; and to the CNPq and FAPEMIG for their financial support.