BLUE AND NEAR ULTRAVIOLET REVERSIBLE PHOTOREACTION IN CONIDIAL DEVELOPMENT OF THE FUNGUS, ALTERNARIA TOMATO

In the sporulation of Alternaria tomato, conidiophores are induced by near ultraviolet irradiation but not by darkness, and the conidia develop only when the irradiation is followed by a period of darkness. Conidial development is suppressed by a short exposure to blue light at a definite time during the dark period following the inductive irradiation. The suppression of conidial development by blue light can be reversed by exposure to near ultraviolet light immediately following the blue light irradiation. This reversion is reversibly suppressed by a further exposure to blue light immediately following near ultraviolet irradiation. Thus, at least two stages are involved in the sporulation of A. tomato, the first being a photochemical stage necessary for the induction of conidiophores, and the second essential for the conidial development which proceeds only in the absence of exposure to the blue region of the spectrum. Moreover, conidial development can be controlled by alternating doses of blue and near ultraviolet light, and the subsequent response depends upon the last kind of radiation given. It is concluded that a new pigment system, which we have named “Mycochrome”, is involved in the blue and near ultraviolet reversible photoreaction, and that this compound plays an important role in the photocontrol of conidial development in this fungus.     

The action of skeleton photoperiods on flowering in Lemna perpusilla

The effects of 24 hr cycle skeleton photoperiodic schedulesinvolving two short light pulses on flowering in Lemna perpusillahave been studied. Simulation of complete photoperiods by correspondingskeletal ones is nearly perfect for all photoperiods up to 8hr and is unstable for periods of 9 to 13 hr. A jump in theresponse phase appears when skeleton photoperiods ranging from12 to 13hr are given. For all skeleton photoperiods longer than14 hr the phase is entrained so that it agrees with that givenby skeleton photoperiods of complemental lengths. That is, askeleton photoperiod of 18 hr is equivalent to that of 6 (=24–18) hr. Simulation is largely related to whether thesecond pulse is locked on to "dawn" or to "sunset" dependingon when it falls during the dark period following the firstpulse. The inductive action of skeleton photoperiods that gives unstableentrainment depends on the length of a preliminary dark periodgiven before the plant receives the first pulse, since in theseskeleton schedules the sensitive zone to the second pulse shiftswith the length of the preliminary darkness. Thus, we tentatively conclude that the circadian oscillationin L. perpusilla involves an entrainment mechanism and thatphotoperiodic induction is contingent on the coincidence oflight and a specific inductive phase in oscillation. (Received September 18, 1968; )     

PHOTOSYNTHETIC NITRITE REDUCTASE FROM SPINACH

Photosynthetic nitrite reductase (PNiR) was purified extensivelyfrom spinach leaves by the method including acetone precipitation,ammonium sulfate fractionations and DEAE-cellulose column chromatography.The purified PNiR had the highest specific activity thus farobtained. Absorption spectrum of the purified PNiR indicatedthat it had no flavin component. There was no difference inthe rate of photosynthetic nitrite reduction between aerobicand anaerobic conditions. In chloroplasts two reductase systems related with ferredoxinhad been recognized, which were ferredoxin-nitrite and ferredoxin-NADPreductase system. The relationship between the two systems wasinvestigated by using the reconstituted enzyme system. Whenthe reduction of NADP was taking place, the reduction of nitritewas strongly inhibited. Some physiological significance of thephenomenon was discussed. ¹This work was mainly perfomed in the Department of Cell Physiology,University of California, during the author's stay, and waspresented in the 6th annual meeting of the Japanese Societyof Plant Physiologists on April 4-7, 1964 in Tokyo.     

Sexual Stages in the Life History of the Hemogregarine Hepatozoon rarefaciens (Sambon and Seligmann, 1907)*

SYNOPSIS. Sexual stages of a reptilian hemogregarine Hepatozoon rarefaciens are described from the hemocoele of a mosquito vector Culex tarsalis. The gametocytes associate within 0.5 hr after biting. Most of the gametocytes then pair off and begin to differentiate. After about 26 hr at 22–23 C, the macrogametocyte usually becomes crescent-shaped with the microgametocyte lying in the concavity. The nucleus of the macrogametocyte enlarges considerably, while the microgametocyte divides into 2 and eventually into 4 spindle-shaped microgametes which are biflagellated. The macrogametocyte increases in size and rounds up to form a macrogamete. Gamete formation is usually completed by 60 hr and fertilization begins soon thereafter. The zygotes develop into the uninucleate oocysts described previously. In some other species of Hepatozoon, gametogenesis has been described as taking place in the stomach of the arthropod vector, with the microgametocytes transforming without cytoplasmic division into non-flagellated microgametes. The occurrence of 2 distinct types of gametogenesis may possibly be a basis for separating Hepatozoon into 2 genera.