The flowering behavior of Pharbitis nil cultured aseptically under various nutritional conditions was studied. The plants were grown under continuous illumination at a temperature of 15°. 1. Optimal flowering responses were observed when the plants were cultured on sucrose (4-10%) media containing 0.75 or 1% agar and with pH values ranging from 4.32 to 5.50. 2. Minerals of White's solution added to the medium had little influence in causing floral initiation; plants initiated floral primordia on agar medium containing sucrose without minerals. On sucrose media containing 0.05-0.1% KNO3 and Ca(NO3)2, the flowering response was slightly suppressed. However, these media promoted vegetative growth. 3. Glucose, fructose, mannose, maltose, lactose and raffinose gave the same effective results as sucrose in causing floral initiation, but xylose, galactose, mannitol and soluble starch were less effective. 4. Sucrose was effective in promoting floral initiation when applied during the period of low-temperature treatment at 15°, and more effective when applied during the early part than when applied during the late part of the low-temperature period.
The rates of O2 uptake and 32PO4- uptake of disks excised from matured tobacco leaves increased as they were floated on water. Kinetin at 10-5M suppressed the increases. KCN inhibited O2 uptake of both kinetin treated and untreated disks, whereas NaF and 2, 4-DNP stimulated O2 uptake of kinetin treated disks, but not that of untreated ones. These results suggest that kinetin may be an inducer of Crabtree effect.
The 36 collections belonging to the complex of Oryza minuta and O. officinalis gathered during a recent exploration of the major islands of the Philippines were studied cytotaxonomically. Chromosome counts showed that 15 collections were diploid (2n=24) and 21 collections were tetraploid (2n=48). Morphological features of the diploids and the tetraploids were compared, and obvious differences were found in spikelet breadth, shape and certain inflorescence features. It was pointed out that these morphological differences are parallel to those between O. minuta and O. officinalis according to Tateoka's8) amended designation. The geographical distribution of the diploids and the tetraploids in the Philippines was surveyed, and some difference in localization was noted. Our field observations were in favor of the assumption that these two taxa were reproductively isolated under natural conditions. It was concluded that the diploid and the tetraploid plants are reasonably separated at the species level: the former falls under O. officinalis while the latter accords with O. minuta.
1. The behaviour of irritable reaction of the parenchymatous cells of the pulvinus was made clear by observing it directly under the microscope by means of electric stimulation. As the symptoms of excitement, rapid vacuole contraction, the deformation of the cell and the diminution in cell volume occurred by stimulation. Sometimes the diminution of cell volume was slight or scarcely observed. These responses were seen in the parenchymatous cells of both the upper and lower halves of the pulvinus alike. This reaction was quite reproducible. If the cells, however, received dratsic stimulation, irreversible reaction occurred. 2. The oscillating phenomenon was demonstrated in the recovery course of the leaf movement. This oscillation movement may be caused by the counteraction of the upper and lower halves of the pulvinus. 3. Based on these findings, some interpretation on the machanism of the seismonastic leaf movement was presented.
In Monostroma fuscum var. splendens the sexual plants and the asexual plants are isomorphic. The sexual plants are dioecious and the sexual reproduction is isogamous. The swarmers are liberated through round pores opening on the same side of the thallus. The gametes are elongated pear-shaped or fusiform, having two flagella at the anterior end. The zoospores are elongated pear-shaped, having four flagella at the anterior end. Both gametes and zoospores have one chloroplast with an eye-spot and a pyrenoid in the posterior part; they are positively phototactic. The gametes conjugate generally side by side to form the zygote. Both zygotes and zoospores germinate by pushing out a protuberance after a resting period. The cell divides with a transverse wall into two parts, one of which elongates and forms the primary rhizoid. By successive cell-divisions the germlings (derived from zygotes or zoospores) develop into a simple filament. Then longitudinal cell-divisions take place and the germlings have a cylindrical structure. After two months the germlings attain about 3mm. in height and develop into a tubular structure with a cavity in cross section. In such tubular structures a split later takes place resulting in an expanded membranous frond of a single layer of cells. After about ten months the plant derived from the zygotes produces 4-flagellated zoospores; the plant derived from the zoospores produces biflagellated gametes. The type of the life history of M. fuscum var. splendens is quite different from those of other Monostroma, which have so far been studied, and it is identical with those of Ulva and Enteromorpha.