Osmotic priming of seed was evaluated as a means of improving stand establishment, early seedling growth, and yield of processing tomatoes (Lycopersicon esculentum Mill. cvs. UC204 and 6203). Seeds were primed in aerated solutions of 3% KNO3 (w/v) or of polyethylene glycol 8000 (PEG) of equivalent osmotic potential (-1.25 MPa; 314 g-kg−1 of water) at 20°C for 7 days, rinsed, and dried in forced air at 30°. Under laboratory conditions, seeds primed in either osmoticum germinated more rapidly than untreated seeds at 20° and 30°. At 10°, the PEG treatment was of little benefit for either variety, while the KN03 treatment still reduced the time to 50% germination to 60% to 80% of the control value. Priming did not affect the final germination percentage. Seedling emergence in the field was evaluated in March and April planting dates. In both trials, seedlings from primed seeds emerged earlier and more uniformly than seedlings from untreated seeds. Seedlings from primed seeds maintained greater mean plant dry weights, leaf areas, and ground cover percentages than untreated seedlings throughout the preflowering period. This advantage was due entirely to early emergence rather than to an increased relative growth rate. The early growth advantage from seed priming did not improve earliness of maturity, total yield, or soluble solids content of fruit.
Present address: Campo Agricola Experimental del Norte de Guanajuato, Apdo. Postal 25, San Jose Iturbide, Gto., Mexico.
Received for publication 14 July 1986. This research was supported by funds from AES/USDA Regional Research Project W-168 and grants from the California Tomato Research Institute, Inc. The technical assistance of Z. Stan Ski-binski and Stacy Lee in some of these experiments is gratefully acknowledged. The cost of publishing this paper was defrayed in part by the payment of page charges. Under postal regulations, this paper therefore must be hereby marked advertisement solely to indicate this fact.