Responses of seeds of Pinus virginiana to light

Abstract

The germination response of seed of Pinus virginiana, to red and far-red radiant energies was measured at 25 C, the temperature found to be optimum for germination of these seeds. The effect of temperature and period of imbibition in total darkness preceding the light treatment was also determined. Very little germination occurred in darkness at any temperature tested unless the seeds were partially afterripened at 5[degree] prior to placing them at the germination temperature. Germination of the seeds was promoted by red (5800-6950 A) and inhibited by far-red (6950-7900 A) radiant energy. About 1 x 106 ergs/cm2 was needed for conversion of 50% of the pigment by red or far-red radiant energy. The maximum germination in response to red was greater if seeds imbibed at 5[degree] than at 25[degree]. Lengthening the period at 5[degree] from 1 hour to 16 hours increased germination in total darkness by 12% for 1 sample and by 62% for another. Lengthening the period at 5[degree], however, increased sensitivity of both lots of seed to promotion by red. The action of the red and far-red radiant energies on the germination of the seeds was immediately and repeatedly reversible. For seeds held at 5[degree] for 1 day a longer period could elapse between the red and far-red treatments and still prevent germination than for seeds held at 5[degree] for 20 days.