Light, oxygen, and temperature requirements for Typha latifolia seed germination

Abstract

Typha latifolia L. seed germination required high temperatures, low O2 concentration, and relatively long exposure to light to induce high percentages of seed germination. A greater percentage of seeds germinated at 35 °C than at lower temperatures. Less than 10% of the seeds germinated at 15 °C and none at 10 °C. For submerged seeds exposed to red light (R), maximum germination was achieved when the O2 concentration in the water was reduced to between 2.3 and 4.3 mg L−1 at 30 °C. Seeds were most sensitive to R when imbibed for 6–24 h. At least 10 h of continuous R (2.5 × 10−8 W m−2) was needed for maximum germination. However, when seeds were exposed to light of the same intensity for four 30-min periods over a 12-h span, the effect was nearly the same as 12 h of continuous light. The germination percentage after the intermittent irradiation was nine times that produced by a single 2-h exposure. Five minutes of far-red light (FR) reversed the effect of 6 h of R to the level of dark controls. The photoreversible effect of FR was less pronounced for seeds imbibed prior to illumination. When spans of R and FR were alternated (FR–R–FR, R–FR–R, FR–R–FR–R, R–FR–R–FR), repeated reversibility was observed. However, FR was progressively less effective in reversing the effect of R.