Overcoming dormancy of seeds of <i>Copaifera arenicola</i> (Ducke) J. Costa &amp; L. P. Queiroz

Gama, Dráuzio Correia; Chambó, Emerson Dechechi; Botelho, Thaís Santana; Freitas, Teresa Aparecida Soares de

doi:10.1590/2317-1545v47295229

ABSTRACT:

Seed dormancy can occur due to a combination of intrinsic factors and stimuli from the external environment. From a production perspective, it is an undesirable characteristic, as it hinders germination and limits production. This study aimed to identify the type of primary dormancy and determine the most efficient method to overcome it in seeds of Copaifera arenicola (Ducke) J. Costa & L. P. Queiroz (Fabaceae), a tree species endemic to the Caatinga. The experiment was conducted in a completely randomized design, with 52 experimental units distributed in 13 treatments with four replications. The treatments included scarification (mechanical and chemical), hot stratification, use of growth regulators, washing/leaching, soaking and control. Germitest paper was used as substrate in germination chambers (B.O.D) under alternating temperatures of 20-30 ± 2 °C and a 12-hour photoperiod (white light). Seeds with root protrusion ≥ 2 mm were considered germinated, evaluated at two-day intervals. The following parameters were analyzed: first count and total germination percentage; mean germination time and rate; speed index, uncertainty and germination uniformity coefficient. The data were subjected to ANOVA, and the means were compared by Tukey test (p ≤ 0.05). The dormancy mechanism identified was physical. The most effective treatments to overcome dormancy were: chemical scarification with sulfuric acid (H₂SO₄-98%) for 10 and 5 minutes; mechanical scarification (abrasion with 100 grit wood sandpaper) without additional treatment; and scarification followed by immersion in potassium nitrate (KNO₃) for 30 minutes.

Index terms:
Caatinga; endemic species; pre-germination test; rapid and uniform germination; seedling establishment

[TFN1] ^a Sources of variation; FGC = first germination count; GP = germination percentage; MGT = mean germination time; MGR = mean germination rate; GUC = germination uniformity coefficient; GSI = germination speed index; U = germination uncertainty. ^b Coefficient of variation in percentage. *Significant at 5% by the ANOVA F-test.

Treatments	Description
CONT	Intact seeds
SS-MEC	Mechanical scarification of seeds rubbed manually on 100 grit wet sandpaper on the opposite side to the hilum, stopping immediately after viewing the cotyledon.
IS-GA₃	Immersion of intact seeds in a concentrated (0.05%) solution of GA₃ (gibberellic acid) for 30 minutes, followed by drying on paper towels.
SS-MEC-GA₃	Seeds scarified with 100 grit wet sandpaper, immersed in a concentrated (0.05%) solution of GA₃ (gibberellic acid) for 30 minutes, and dried on paper towels.
IS-KNO₃	Immersion of intact seeds in a concentrated (0.2%) solution of KNO₃ (potassium nitrate) for 30 minutes, followed by drying on paper towels.
SS-MEC-KNO₃	Seeds scarified with 100 grit wet sandpaper, immersed in a concentrated (0.2%) solution of KNO₃ (potassium nitrate) for 30 minutes, and dried on paper towels.
SS-H₂SO₄-5’	Immersion of intact seeds in a concentrated (98%) solution of H₂SO₄ (sulfuric acid) for five minutes, followed by washing under running water until complete removal of acid residues and subsequent drying on paper towels.
SS-H₂SO₄-10’	Immersion of intact seeds in a concentrated (98%) solution of H₂SO₄ (sulfuric acid) for 10 minutes, followed by washing under running water until complete removal of acid residues and subsequent drying on paper towels.
IS-H₂O-40°	Hot stratification with immersion of intact seeds in warm distilled water (40 °C) until reaching ambient temperature, followed by drying on paper towels.
IS-H₂O-80°	Hot stratification with immersion of intact seeds in hot distilled water (80 °C) until reaching ambient temperature, followed by drying on paper towels.
IS-SK-24h	Soaking with immersion of intact seeds in distilled water (ambient temperature) for 24 hours, followed by drying on paper towels.
IS-PRW	Prior washing of seeds in running water, followed by drying on paper towels.
IS-PRW-SK-30’	Prior washing of seeds in running water, drying on paper towels and subsequent soaking for 30 minutes in distilled water.

SV^a	F value	CV (%)^b
FGC	13.080^*	94.20
GP	4.175^*	7.20
MGT	27.710^*	11.82
MGR	49.597^*	10.24
GUC	24.501^*	65.87
GSI	31.476^*	15.59
U	11.696^*	16.22

TREAT^a	*FGC (%)	*GP (%)	MGT (days)	MGR (days^-1)	GUC (days^-2)	GSI (seeds.day^-1)	U (bits)
CONT	0.0 c	67.0 c	22.2 b	0.045 b	0.0204 c	0.875 c	0.166 ef
SS-MEC	9.0 b	82.0 b	11.0 a	0.090 a	0.1206 bc	1.964 bc	0.107 c
IS-GA₃	1.0 c	64.0 c	20.8 b	0.049 b	0.0178 c	0.941 c	0.160 ef
SS-MEC-GA₃	0.0 c	79.0 b	10.8 a	0.093 a	0.3638 b	1.891 bc	0.090 b
IS-KNO₃	0.0 c	65.0 c	20.2 b	0.049 b	0.0221 c	0.950 c	0.158 ef
SS-MEC-KNO₃	0.0 c	89.0 ab	9.6 a	0.104 a	0.7653 a	2.361 b	0.053 a
SS-H₂SO₄-5’	15.0 a	92.0 a	10.7 a	0.094 a	0.1102 bc	2.441 b	0.143 e
SS-H₂SO₄-10’	7.0 b	92.0 a	09.8 a	0.102 a	0.2230 b	2.514 a	0.119 d
IS-H₂O-40°	1.0 c	77.0 bc	20.5 b	0.048 b	0.0159 c	1.134 c	0.188 f
IS-H₂O-80°	0.0 c	80.0 b	19.1 b	0.052 b	0.0232 c	1.219 c	0.184 f
IS-SK-24h	1.0 c	71.0 bc	19.9 b	0.051 b	0.0165 c	1.081 c	0.172 f
IS-PRW	3.0 bc	62.0 c	20.7 b	0.048 b	0.0160 c	0.948 c	0.157 ef
IS-PRW-SK-30’	0.0 c	64.0 c	20.5 b	0.049 b	0.0173 c	0.935 c	0.162 ef
CV	94.2%	7.2%	11.8%	10.2%	65.9%	15.6%	16.2%

Overcoming dormancy of seeds of Copaifera arenicola (Ducke) J. Costa & L. P. Queiroz

ABSTRACT: