This work investigates the potential propagation by seed and cuttings of the Azorean native
Since the first LIFE financed project directed to the habitat restoration of the Azorean bullfinch, the Regional Forestry Services holds the production of the autochthonous trees species, excluding the production of small shrubs like
Today heathlands restoration combines different techniques including mechanical disturbance, low intensity grazing and fires, transference of soil blocks with plants and/or seeds, seeding using fruiting branches or capsules, and planting potted plants grown in nurseries [
Previous studies on
In order to identify these potential differences that are useful to the regional projects dealing with the propagation of the Azorean heather, we studied the effect of light and temperature regime on seed germination and the effect of storage period, storage temperature, and surface sterilization of seeds on seed germination. In addition we studied the effect of cutting’s harvesting month, cutting type, substrate, and cultural conditions on rooting induction.
Seeds were harvested at Tronqueira, a region belonging to the Natural Park of São Miguel Island, and under intervention of the “Lands of Priolo” LIFE project. Capsules of
Seed surface sterilization was only performed with a lot of 108 days stored seeds, since nonstored seeds presented a percentage of germination above 90 without sterilization. Before sowing, seeds were soaked in a 0.6% benomyl solution (Benlate) for 30 min, rinsed 3 times with sterile distilled water, soaked in a 10% commercial bleach solution with 0.01% Tween 20 (Sigma) for 20 min, and finally rinsed six times with sterile distilled water. All the seeds were sown in Petri dishes, but surface sterilized seeds were sown on sterilized material. Lots of 100 seeds were placed on filter paper (Whatman number 1) moistened with distilled water, in 12 cm diameter Petri dishes sealed with laboratory film (parafilm “M”). The germination trials were carried out in germination chambers with automatic control of light (light intensity ~56
The number of seeds showing radicle emergence was recorded every week. For each different temperature and light regime, four replicates of 100 seeds were set up [
Stem cuttings were collected from approximately 200 adult shrubs of a wild population at Lombadas (São Miguel Island), in October 2011, February 2012, and March 2012. Cuttings were sprayed with tap water, placed inside polyethylene bags, and transported in approximately 40 minutes to the laboratory. The cuttings were then placed in tap water and the following types of cuttings with 4 to 7 cm long were prepared: straight, mallet, and heel cuttings from vegetative stems. In October straight cuttings from stems with remains of dry capsules were also done and identified as cuttings from reproductive stems. Foliage was removed from the basal 2-3 cm of each cutting and in the reproductive stems the remains of dry capsules were also removed.
Four types of rooting substrates were tested: (a) native soil, (b) native soil: horticultural coarse perlite (
The study was carried out with four replicates in a randomized blocks design. Ten cuttings per replicate were used. The number of cuttings showing roots was recorded after 12 weeks in culture. For the variable “percent of rooting,” a
The shortest photoperiod (8 h/day) significantly increased the germination percentages but did not significantly decreased the number of days to first radicle emergence or the mean time of germination (Table
The effect of light regime on the germination characteristics of
Photoperiod |
Number of seeds | Days to first radicle emergence | Mean time of germination (days) | Percent germination |
---|---|---|---|---|
8 | 4 × 100 | 15 ± 1.7a | 34 ± 3.0a | 90 ± 7.0a |
16 | 4 × 100 | 21 ± 3.8a | 41 ± 3.9a | 70 ± 7.9b |
The significantly highest percentages of germination were obtained with the temperatures regimes of 10°C and 15°C, but the temperature regime of 10°C significantly delayed the mean time of germination. The number of days to first radicle emergence was not significantly different within the temperatures regimes tested (Table
The effect of temperature regime on the germination characteristics of
Temperature regime (°C) | Number of seeds | Days to first radicle emergence | Mean time of germination (days) | Percent germination (at day 126) |
---|---|---|---|---|
10 | 4 × 100 | 17 ± 2.0a | 44 ± 3.1a | 93 ± 5.8a |
15 | 4 × 100 | 15 ± 1.7a | 34 ± 3.0b | 90 ± 7.0a |
20 | 4 × 100 | 15 ± 1.5a | 33 ± 5.2b | 65 ± 6.8b |
20–10 | 4 × 100 | 17 ± 1.0a | 32 ± 2.8b | 74 ± 6.5b |
Seeds with 6 days of storage presented significantly superiors percentages of germination and mean times of germination. The number of days to first radicle emergence was not significantly different within the storage periods tested (Table
The effect of storage period at room temperature on the germination characteristics of
Storage period at room temperature before trial (days) | Number of seeds | Days to first radicle emergence | Mean time of germination (days) | Percent germination |
---|---|---|---|---|
6 | 4 × 100 | 17 ± 2.0a | 44 ± 3.1a | 93 ± 5.8a |
108 | 4 × 100 | 7 ± 2.0a | 30 ± 1.5c | 52 ± 13.0b |
270 | 4 × 100 | 12 ± 3.0a | 37 ± 2.2b | 41 ± 16.3b |
Seeds stored at 4°C showed significantly superior percentages of germination regarding those stored at room temperature, but the number of days to first radicle emergence and the mean time of germination were not significantly different (Table
The effect of storage temperature on the germination characteristics of
Storage period and temperature | Number of seeds | Days to first radicle emergence | Mean time of germination |
Percent germination |
---|---|---|---|---|
270 days at 4°C | 4 × 100 | 11 ± 2.5a | 34 ± 5.6a | 71 ± 7.9a |
270 days at room temperature | 4 × 100 | 12 ± 3.0a | 37 ± 2.2a | 41 ± 16.3b |
At the end of this germination test (day 112), only part of the nongerminated seeds without surface sterilization presented contamination, while none of the surface sterilized seeds presented contamination. Seeds surface sterilized showed significantly superior percentages of germination regarding the control, while the velocity of germination was not affected (Table
The effect of surface sterilization on the germination characteristics of
Surface sterilization | Number of seeds | Days to first radicle emergence | Mean time of germination (days) | Percent germination |
---|---|---|---|---|
Yes | 4 × 100 | 7 ± 2a | 30 ± 2.6a | 78 ± 14.1a |
No | 4 × 100 | 7 ± 2a | 30 ± 1.5a | 52 ± 13.0b |
The rooting response was influenced by the type of stem cutting. Significantly inferior percentages of rooting were found for mallet cuttings, either for cuttings harvested in October and planted in peat : perlite (1 : 1) or for cuttings harvested in March and planted in native soil : perlite (3 : 1) substrate, both under a temperature of 20°C and a 16 h photoperiod (Table
Rooting percentages obtained on different types of cuttings of
Type of stem cutting |
|
October |
|
March |
---|---|---|---|---|
Heel | 4 × 10 | 50.0 ± 14.1a | 4 × 20 | 90.0 ± 13.5a |
Reproductive | 4 × 10 | 30.0 ± 7.1ab | — | — |
Straight | 4 × 10 | 25.0 ± 7.1bc | 4 × 20 | 96.3 ± 4.8a |
Mallet | 4 × 10 | 10.0 ± 7.1c | 4 × 20 | 70.0 ± 16.3b |
For a total of 160 heel cuttings harvested in March and planted in native soil : perlite (3 : 1) substrate, the rooting percentages were not significantly affected by cultural conditions: 90.0% ± 13.5 at the growth chamber (20°C, 16 h photoperiod) and 87.5% ± 11.9 outdoors.
For a total of 80 heel cuttings, planted outdoors in native soil : perlite (3 : 1) substrate, the rooting percentages were significantly influenced by the harvest month: 95.0% ± 10.0 for cuttings harvested in March and 70.0% ± 5.0 for cuttings harvested in October.
For heel cuttings harvested in March and planted outdoors, the rooting response was influenced by the substrates used. The rooting percentages were significantly superiors for cuttings planted in native soil or native soil : perlite (3 : 1) substrates (Table
The effect of substrate type on the rooting percentages of
Substrate |
|
Percent rooting |
---|---|---|
Native soil | 4 × 10 | 80.0 ± 10.0a |
Native soil : perlite (3 : 1) | 4 × 10 | 95.0 ± 10.0a |
Peat : Perlite : vermiculite (2 : 1 : 1) | 4 × 10 | 62.5 ± 9.6b |
Peat : perlite (1 : 1) | 4 × 10 | 45.0 ± 12.9c |
Germinationof
In this study we have found some ecotypic differences for characteristics of adaptive significance related to the germination characteristics. The Azorean seeds of
The authors declare that they have no conflict of interests.
The authors thank the referees for their constructive and helpful comments and suggestions for this paper. This work was supported by Geotrota Lda., (