The dark fixation of CO2 in lakes with different trophic types was investigated. Non-photosynthetic CO2 assimilation by phytoplankton was negligibly small compared with photosynthetic assimilation. High activities of dark fixation of CO2 were observed in meromictic lakes and stagnant waters, where the dark CO2 fixation occupied 10-40% of total photosynthetic production. This can be attributed to the bacterial biosynthetic action. An importance of the dark fixation of CO2 in trophic dynamics was discussed.
Growth of some variants of tobacco plants, known to be deficient in chlorophyll, was comparable to that of normal green variants. Three variants of Nicotianatabacum (“Bright Yellow”) “Burley 21” and Shirogiri”., as well as N. sylvestris, were examined with respect to the relationship between chlorophyll content and photosynthetic CO2 uptake. In three of the four materials examined we found that the photosynthetic CO2 uptake was in proportion to the chlorophyll content. “Burley 21”. containing 1/2 to 1/10 of the amount of chlorophyll of normal plants of the same age, grew as well as “Bright Yellow” (normal green). For young and old leaves of a normal green variant, CO2 uptake was saturated at about 20, 000lux, whereas with old leaves of a virescent variant, the rate of CO2 uptake was still increasing at 40, 000lux. At this intensity old and young leaves of both variants showed similar rates of CO2 uptake per unit leaf area, but on a chlorophyll basis the leaves of the virescent were two to twenty times more active than those of the normal. Photochemical reaction measurements on chloroplasts also showed that the activity of chloroplasts from old leaves of the virescent was the highest of all. The rates of photosynthetic CO2 uptake of young leaves of both variants continued to rise with temperature, but that of old leaves of the virescent variant was rather low at higher temperature.
A study was made on a genetical control of nuclear conjugation in doubly compatible di-mon matings, using Coprinus macrorhizus f. microsporus. By crossing each of different monokaryons with a standard one for five successive generations, isogenic monokaryons in regard to the modifiers which seem to be independent of the incompatibility factors and seem to control nuclear conjugation, were produced. By using these isogenic monokaryons and original ones, two series of experiments were conducted. First, doubly compatible di-mon matings were made, in each of which one nucleus of the dikaryon was isogenic with the nucleus of the monokaryon and another nucleus of the dikaryon was original. In each of the above matings, the original nucleus of the dikaryon always conjugated with the nucleus of the monokaryon without any exception. Secondly, doubly compatible di-mon matings were made, using isogenic monokaryons only. The nuclear constitutions of the resulting dikaryotic hyphae were of two kinds in each mating. From these results, it was revealed that the selective conjugation of nuclei in doubly compatible di-mon matings was caused by the difference of the modifying alleles.
The development of protonemata and the formation of the leafy shoot of Tetraphis pellucida were investigated. The protonemata of this species consist of four elements i. e., the chloronemal and the caulonemal filaments with many branches, the spathulate thallose protonema composed of a single layer of cells, and the rhizoids. As to the formation of the thallose protonema two patterns were recognized: one was the formation directly from a terminal cell of the chloronemal branch and the other from a cell of the basal part of the young leafy shoot. In many cases, the second and the tertiary thallose protonemata were successively differentiated from the basal part of the primary one. As to the formation of the initial cell of the leafy shoot two patterns were recognized: one was the formation from a basal cell of the thallose protonema and the other from a cell of the caulonema without the agency of the thallose protonema. Three to four leafy shoots were successively produced from one leafy shoot.