A. Lippai et al., EFFECTS OF TEMPERATURE AND WATER POTENTIAL ON GERMINATION OF HOREHOUND (MARRUBIUM-VULGARE) SEEDS FROM 2 AUSTRALIAN LOCALITIES, Weed science, 44(1), 1996, pp. 91-99
Horehound seed from Wyperfeld (Wyp90 and Wyp93) had optimum germinatio
n (98%) at constant 25 C and alternating 30/15 C at 0 MPa, while seed
from Swift's Creek (SC93) had optimum germination at constant 25 to 27
C (84%) or alternating 25/15 C (95%). The Generalized Additive Models
showed the effects of the three covariates (temperature, temperature
difference and water potential) followed a smooth and regular pattern.
Germination of SC93, Wyp90 and Wyp93 seed increased (P < 0.001) by 9.
1, 6.1, and 11.6% for each degree increase in temperature difference b
ut decreased (P < 0.001) with decreases in water potential by a factor
of 4.1, 4.8, and 7.1 respectively, and ceased at -1.5 MPa. At constan
t temperatures the odds of germination were 27, 19, and 18% smaller fo
r water potentials of 0, -0.25 and -0.5 MPa than when alternating temp
eratures varied by 15 C.