Photocontrol of Rough Cinquefoil Seed Germination and its Enhancement by Temperature Manipulation and KNO3

Abstract

Imbibed seeds of rough cinquefoil (Potentilla norvegica L.) remain dormant in darkness at constant and alternating temperatures. Full promotion of germination resulted after 3 days' dark imbibition at 25 C followed by 24 hr of continuous unfiltered fluorescent light. Germination was controlled by phytochrome. The sensitivity of the seeds to short light exposures was increased by the introduction of a temperature shift to 40 C for 2 hr, at the conclusion of the normal dark imbibition period at 25 C. The temperature shift also reduced the time required in continuous light to give full promotion of germination. The response to light was synergistically increased when the seeds were imbibed in 0.2% KNO3, and given the temperature shift. Nearly full promotion was reached with ca. 5 min of red light, and 50% germination occurred with as little as 1 sec. The system was still under phytochrome control. These findings suggest a mechanism by which soil populations of weed seeds may become physiologically conditioned to respond to very brief exposures to light.