The light promoted germination of the seeds of Chenopodium album L. III. Effect of the photoperiod during growth and development of the plants on the dormancy of the produced seeds

The effects of three photoperiodical conditions during the growth of the mother-plants of Chenopodium album L. on the induction of dormancy in their seeds were determined : a longday cycle of 18 hours light (LD), a short-day cycle of 8 hours light (SD) and a short-day cycle with an interruption of one hour red fluorescent light in the middle of the dark period (SDR). The course of the germination behaviour of the seeds during dry storage at room temperature and the morphological differences between the seeds revealed the presence of two types of seed dormancy. LD and SDR can induce the first type but only during the period after full flowering of the plants. It is concluded that the level of the active form of phytochrome (Pfr) has an important regulating function during this induction. It is discussed whether it depends on an inhibitor present in the embryo-perisperm complex of the seeds. The second type of dormancy can be induced only by LD conditions. The plants are sensitive to this effect during the complete life cycle. Its induction seems to be related to the length of main light period per cycle and so probably to the photosynthetic activity of the plants. It is correlated with a thick seed-coat and a low seed-weight, and depends on these morphological characteristics. After about three months of dry storage only the second type is present in the seeds, the first one has been inactivated or has disappeared.