Incubation of aerobic cultures of Saccharomyces cerevisiae with high concentrations of glucose leads to the repression of heme biosynthesis [I] and to the accumulation of prototetrahydroporphyrin IX, a pigment with an absorption maximum at 503 nm,

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The influence of light, gibberellic acid, and abscisic acid on unrolling of etiolated barley leaf segments was investigated. Gibberellic acid stimulated unrolling of both illuminated and nonilluminated leaf segments. In contrast, abscisic acid prevented light-stimulated unrolling and abolished the slight unrolling of segments maintained in the dark.Analysis of the time course of photoinduced unrolling showed a lag period of 6 hours before the onset of rapid leaf unrolling. The application of gibberellic acid to illuminated segments shortened this lag phase. Also, incubating the segments in buffer in darkness prior to illumination eliminated the lag period. Inhibitors of RNA and protein synthesis prevented light-and gibberellic acid induced unrolling, indicating a requirement for macromolecular synthesis. The possibilities that the lag period of unrolling following illumination represents the time required for the removal of endogeneous inhibitor or the synthesis of essential macromolecules are discussed.In etiolated grass seedlings the first leaf remains tightly rolled even when it penetrates the coleoptile; however, upon illumination this leaf unrolls rapidly. Leaf unrolling is caused by a greater growth of the cells of the upper mesophyll as compared to the remamiing mesophyll (2). Virgin (10) The present studies were undertaken in order to delineate the time course of events in the leaf unrolling process of barley as influenced by hormones and light. MATERIALS AND METHODSBarley seeds (Hordeum vulgare, L., var. Arivat) were soaked for 8 hr in aerated deionized water. The seeds were then placed between layers of cheesecloth on a stainless steel gauze supported by a 4-liter beaker containing 3.5 liters of aerated 2 mm CaSO4 solution (6). The seedlings were grown in darkness at 25 C for 6.5 days. All subsequent manipulations were carried out under a dim green safelight.Sections, 7 mm in length, were cut from the primary leaves starting 1 cm below the tip. In the leaf unrolling studies samples of 10 segments were floated on 10 ml of 0.001 M sodium acetate buffer, pH 5.5, containing the test chemicals, and incubated at 25 C. Stock solutions of the inhibitors were prepared in sodium acetate buffer. Stock solutions of GA and ABA were prepared by dissolving the compounds in 0.001 M sodium acetate and adjusting to pH 5.5 with 0.001 M acetic acid.Leaf width was determined by arranging segments, which had been blotted dry, on a glass plate fitted to an overhead projector. The enlarged image (X4) was projected onto a screen and measured. RESUlLTSWhen floated on buffer and illuminated, segments of the etiolated primary leaf of barley unroll and turn green. For the first 4 to 6 hr following illumination unrolling is slow; there is then a period of rapid expansion lasting approximately 6 hr followed by a period of less rapid unfolding (Fig. 1). Leaf unrolling is complete after about 24 hr. In contrast to the illuminated segments, those floated on buffer in the dark unroll much less. The small amount of unrolling tha...

The changes in protein content of pea cotyledons have been followed during the period from 9 to 33 days after flowering. Initially protein content increased gradually with a rapid period of deposition occurring between days 21 and 27 after flowering. After the 28th day the rate of accumulation of protein declined as the seed dehydrated and matured. At maturity the pea cotyledon contained approximately 25 % protein which was divided into albumins and globulins in the ratio of 1:1.4.Analytical data and the incorporation of exogenously supplied '4C-leucine indicated that albumins were synthesized early in cotyledon development whereas globulin synthesis predominated with increasing maturity. In view of these changes in the rate and pattern of protein synthesis during seed maturation, the developing pea cotyledon provides a convenient system in which to study the control of protein synthesis. In the present study variations in the capacity for exogenous amino acid incorporation in vivo have been examined, and attempts have been made to relate these changes to alterations in the capacity for cell-free amino acid incorporation. MATERIALS AND METHODSSeeds of an early dwarf variety of pea (Pisum sativum L., var. Burpeana) were planted in pots in a soil-peat-perlite (1: 1 :1) mixture and maintained in a greenhouse under a 16-hr photoperiod. Supplemental illumination was provided by fluorescent and incandescent lighting. Application of fertilizers N:P:K (200, 40, 160 ,ug/g) and 75 mm Ca(NO4) were made on alternate days.Under this culture regime the plants flowered a month after the seeds had been sown. The date of full bloom was recorded for each individual flower and used as the zero date in developmental studies. At intervals following flower, the fruits were collected from the two lowest pod-bearing nodes. In general, 10 pods were collected for a specific developmental stage, and a random sample of the peas from these pods was then prepared. The testa and the embryonic axis were removed from the seed, and the cotyledons were used for analysis.In Vivo Amino Acid Incorporation and Protein Fractionation. Two microliters of '4C-L-leucine (240 mc/mmole, 100 ,tc/ml) were injected through the pod into each cotyledon of intact pea seeds which were left in situ in the detached pods. After a 3-hr incubation the seeds were removed from the pod and the cotyledons were recovered. Albumin and globulin fractions were prepared from the cotyledons by modifications of the method of Danielson (6). Twenty cotyledons from peas which had been injected 3 hr previously with "4C-L-leucine were homogenized in a VirTis tissue homogenizer at medium speed for 15 min with 30 ml of 0.2 M NaCl in 20 mm phosphate buffer, pH 7.0. The homogenate was stirred at room temperature for 4 hr and then centrifuged at 1 0,000g for 30 min. The supernatant was brought to 70% saturation by the stepwise additions of (NH4)2SO4 and allowed to stand in ice for 30 min. The precipitate was collected by centrifugation and dissolved in 20 ml of 0.2 M NaCl in 20 m...