Germination of the edible burdock (Arctium Lappa L.) seeds (II)

Effect of the wave length of radiation on the germination

Abstract

It was reported already by the author that the germination of edible burdock seeds is promoted by light. The effect of the wave length of radiation on their germination is studied in this report.
At first, these seeds were, germinated in Petri-dish under natural room-light, fluorescent light and electric light. Secondly, they were germinated under colored paper. Colored paper was sticked, keeping the color side down, to the cover glass of Petri-dish in which the germination was made. Thirdly, the colored glass filters furnished by the Mazuda Institute were used. Spectral transmission curves of these filters are given in fig. 1 and 2. These filters of 5cm square, individually or com-binedly, fixed to the lids of dark boxes. Petri-dishes were put in these boxes. The Petri-dishes with colored paper or the dark boxes with fliters were put under fluorescent or electric light. The ger-mination of edible burdock seeds was attained perfectly under natural room-light or fluorescent light, but was often inhibited considerably under electric light. This fact is probably due to the inhibitive action of ultra-red rays which are conta-ined much more in the electric light. Inside the Petri-dish covered with colored paper, the germi-nation was inhibited extremely under green or blue paper, and promoted under red or yellow paper. This inhibitive action of green or blue paper seems to be mainly due to the ultra-red rays reflected by the above colored paper, and partially due to the green or blue rays reflected also by them.
In the case of the germination under glass-filters, it was promoted under V-R; V-O, V-Y, V-A which transmit wave length of 550_??_700 mμ under fluore-scent light, inhibited to some degree under V-G 1, V-132, V-V 2 which transmit 400_??_500 mμ and inhibited extremely under (V-V1×V-R) or (V-C1×V-R) which transmits 700mμ or above under electric light and 700_??_760mμ under fluorescent light. Under filter IR-D 1 which transmits the ultrared rays 800mμ or above, the germination rate becomes somewhat higher again. Under short ultrared rays, the very small degree of dormancy is detect. ed, that is, seeds that germinate perfectly in the dark often show some depression of germination rate under these rays. Above results agree well with those of FLINT, MEISCHKE or TOOLE et al.
According to the author's other studies, about the same results were obtained in the germination of Mitsuba (Cryptotaenia japonica) and ramie seeds which were favored by light, and in the germination of vegetable seeds of Cucurbitaceae and Solanaceae, and Amaranthus seeds which 'were favored by dark. Putting together reports of MEISCHKE, FLINT, etc. and mine; it is very ineteresting that the germination of light-affected seeds all show about the same reaction to the wave-length of radiation whether they are lightfavored (edible burdock, lettuce, etc.) or darkfavored (Amaranthus, egg-plant, etc.), whether their light-reaction is made mainly in the seed coat (edible burdock, Amaranthus retroflexus, etc.) or in the embryos (Cucurbitaceous vegetables, eggplant, etc.), and whether their light-reaction diminishes with age of seed (dormant) (edible burdock, lettuce, etc.) or not (non-dormant) (Cucurbitaceous vegetables, egg-plant, etc.).