A comparison has been made of the progress of senescence in the first leaf of 7-day-old oat plants (Avena sativa cv. Victory) in darkness and in white light. Light delays the senescence, and intensities not over 100 to 200 ft-c (1000-2000 lux) suffice for the maximum effect. In such intensities, chlorophyll loss and amino acid liberation stiOl go on in detached leaves at one-third to one-half the rate observed in darkness; however, when the leaves are attached to the plant, the loss of chlorophyH in 5 days is barely detectable. (17); in the last instance, a long photoperiod was found more effective than a short one. In rice, red light was effective in delaying senescence and far red had the opposite effect (16). In the presence of EDTA, however, white light was reported to promote bleaching (11), and although this effect has twice been confirmed (9, 23), its relationship to normal senescence in light is not clear. Recently, Takegami (20) has found light to prevent the decrease in total RNA which occurs in senescing tobacco leaves. The effect differed in the different fractions, the fall in 16S and 23S components being somewhat inhibited, whereas the 18S and 25S fractions were actually increased by white light.

Studies of the disposition of hydrazine administered to mammals have not succeeded in accounting for more than a modest fraction of the dose, nor have the excretory products been completely identified. We have utilized 15N-labeled hydrazine and conventional methods to account for about 75% of single doses of about 0.5 LD50 (1 mmol/kg). In 48 h, about 30% appeared in urine as hydrazine and about 20% emerged as a derivative that is acid-hydrolyzable to hydrazine. About 25% was converted to N2 gas, most of which appeared less than 30 min after administration. The percentage converted to N2 at 4 h increased only slightly with dose between 0.5 and 2.0 mmol/kg. Disappearance of hydrazine from blood was biphasic with half-times of 0.74 and 26.9 h.

No abstract