TABLE 1.

Effects of chemical treatments on laccase induction, final dry weight, and LPO levels in liquid cultures of R. solani^a

Treatment	LPO	Dry wt	Relative laccase induction	Mycelial morphology
Compounds affecting calcium signaling
Amphotericin B	1.30**	0.93	5.0**	Pale mycelium, many loose sclerotia
CaCl2	0.76**	1.03	1.5*	No effect
Ionophore A23187	1.03	1.01	13.6**	No effect
LiCl	ND	0.70**	2.0**	Whole mycelium with brown pigmentation
Compounds affecting cAMP signaling
Caffeine	1.65**	0.88*	4.1**	Heavy sclerotization
cAMP	0.57**	0.79**	2.3**	Heavy sclerotization with pale aerial mycelium
Heavy metal salts
CuSO4	2.21**	0.85*	1.8*	Heavy sclerotization
MnSO4	1.03	0.97	2.9*	Heavy sclerotization with brown exudate
Simple organic compounds
p-Anisidine	1.02	0.99	6.1**	Whole mycelium purple-brown pigmentation
Ethanol	2.18**	0.96	3.5**	Pale mycelium, no sclerotia
Isopropanol	3.75**	0.44**	14.1**	Pale mycelium, no sclerotia
Paraquat	3.83*	0.38**	2.7**	Pale mycelium, no sclerotia
Purified P. fluorescens metabolite
Viscosinamide	1.08	0.97	1.1	Aerial mycelium reduced at mat periphery

^aRelative laccase induction was calculated by comparison of the mean peak laccase activity in control and induced cultures; values for LPO and final dry weight are relative to internal controls for each experiment. The mean LPO level of control cultures (pooled from all experiments) was equivalent to 0.257 mM malonaldehyde per g (dry weight) of mycelium (SEM < 4%). No LPO data are available for lithium chloride treatment, as this interfered with the assay. The mean dry weight of control cultures (pooled from all experiments) was 0.213 g (SEM < 1%). Significance was assessed by t test (**, P < 0.01; *, P < 0.05). ND, not determined.