No abstract

A nitrogen source was needed for the flowering of Lemna gibba L., a long‐day plant, and L. perpusilla Torr., a shortday plant. The level of endogenous amino acids analyzed by an Amino Acid Analyzer, rose during the first few inductive cycles, but was reduced during later stages of the flowering process. Serine and threonine levels increased during the light period and decreased during the dark period in L. perpusilla. Exogenous serine and threonine added to the culture medium at 10−6M increased the rate of flowering by more than 35% over the controls. Cysteine inhibited flowering, while other amino acids had little or no promotive effect on flowering. Serine and threonine increased flowering rate in L. perpusilla only when added during a dark period of the inductive cycle. The addition of amino acids during a light period not followed by a dark period had no effect on flowering.

Lycopenc biosynthesis of parenchyma chromoplasts was studied in detached tomato fruits, Lycopersicum esculentum Mill, cv. Waltham Forcing, and found to be phytochrome mediated. A few minutes of red light during the day enhanced lycopene formation. Far‐red irradiation did not enhance lyco‐pene biosynthesis. Far‐red following red nullified the promotive effect of red light. Lycopene content increased two‐fold in the presence of abscisic acid. Ripening of tomatoes was inhibited when gibberellin, kinetin and ascorbic acid were applied to green tomatoes. Gibberellin (A3) was more inhibitory to lycopene synthesis than kinetin.

No abstract

Leaf dises of Xanthium pensylvanicum floated on 0.01 M sucrose solutions inside Petri dishes incubated in a growth chamber at 22°G with illiumination of 3000 lux for 16 to 24 hours of light lost 90% of their chlorophyll. Similar dises floated on water under the same conditions lost 60% of their chlorophyll by the end of one week. chlorophyll degradation calculated as percent of the optical density of the original chlorophyll content accelerated with time. A minimum light intensity of 2000 lux is required for such degradation. Higher intensities accelerated chlorophyll degradation. Glucose, ribose, and xylose have effects similar to sucrose on chlorophyll destruction in the presence of light. chlorophyll degradation was found to be temperature sensitive. There is no difference in chlorophyll content in the presence or absence of sucrose at 10 °C.