Field Emergence of Tomato, Carrot, and Onion Seeds Primed in an Aerated Salt Solution

Abstract

Abstract Conditions for priming tomato (Lycopersicon esculentum Mill.), carrot (Daucus carota L.), and onion (Allium cepa L.) seeds in solutions of K3PO4 + KNO3 and K2HPO4 + KNO3 were optimized in a series of laboratory and field experiments. When primed in K3PO4 + KNO3 (−1.6 MPa) for 7, 14, or 21 days at 15°, 20°, or 25°C, the percentage of emergence was unchanged in tomato, increased in carrot, and decreased in onion. Although there were some species differences, all priming treatments reduced time-spread and increased median rate of emergence. For this solution, priming at 15° for 14 days was optimal for all 3 species. Detailed experiments using optimized priming solutions in an aerated column for tomato (K2HPO4 + KNO3, −1.0 MPa) and for carrots (K3PO4 + KNO3, −1.5 MPa) demonstrated that 18 days was necessary to prime tomato seeds maximally by reducing the time-spread of germination from 73 to 12 hr. With carrots, the maximal response was obtained after 16 days of priming. For both species, continued gains in germination could be obtained from prolonged priming, although only at the expense of a reduced percentage of germination. Air-drying and storing of tomato and carrot seeds for up to 28 days had no effect on subsequent emergence in the field. Conversely, air-drying of onion seeds reduced the percentage of emergence and increased time-spread and rate of emergence. In contrast, salt-primed tomato seeds exhibited an increase in percentage and rate of emergence, and a decrease in time-spread of field emergence. Primed carrot seeds exhibited a faster rate of field emergence than those not primed.