In 7-to 10-day-old leaves of etiolate(I barley (Hordeum vulgare), all of tile eiizymes that convert 1-aminolevulinic acid to chlorophyll are nonlimiting duri-ing the first 6 to 12 hours of illumination, even in the presence of iinhibitors of protein synthesis. The limiting activity for chlorophyll synthesis appears to be a protein (or proteins) related to the synthesis of 6-aminolevulinic acid, prestumably i-aininolevtulinic acid synthetase. Protein Schiff and Epstein (26), and others have suggested that the rate of ALA synthesis is controlled by a negative feedback in which protochlorophyllide or the protochlorophyllide holochrome inhibits the activity of ALA-synthetase. Gassman and Bogorad (5, 6) have proposed the hypothesis that light regulates chlorophyll synthesis in young bean leaves but that synthesis of RNA was required as a precursor step in this process.In this paper we shall present further evidence to support the hypotheses that light stimulates the synthesis of an enzyme which forms 6-aminolevulinic acid, that this is the rate-limiting enzyme in chlorophyll synthesis, and that, at least in barley, RNA synthesis may not be required for early chlorophyll synthesis. METHODS AND MATERIALSBarley (Hordeum vulgare var. Wong; W. A. Burpee Co., Philadelphia, Pa.) seedlings were grown in vermiculite beds in the dark in closed cabinets. The seedlings were watered with tap water every second day. The temperature in the growth room was regulated at 25 i 2 C. The growth rate of the seedlings is shown in Figure 1. The period of most rapid growth was over after 7 days. The first leaf was almost fully formed at this time. A second, smaller leaf appeared after 10 days. Unless noted otherwise, seedlings, 7 to 10 days old, were used.All handling of the seedlings was performed under dim, green safelight (less than 1 ft-c with a filter combination that passed only 540-560 nm of light). The dark-grown seedling "tops" were harvested by cutting them off just above the bed; the lowest inch (approximately the coleoptile region) was discarded in seedlings older than 7 days. Approximately 10 g of seedling tops, prepared as above, were placed in 15-mi beakers containing 6 ml of solution, with the bottom 3 cm of the tops immersed in the solution usually for 2 hr in the dark before illumination. The uptake of solutions was facilitated by gently circulating air around the tops with a small fan (40 cubic feet per min). The solutions in the beakers were replenished to ensure maintenance of turgor of the seedlings throughout the experiment. That a 2-hr dark preincubation permitted adequate uptake of solution by the leaves was shown by the following observations. (a) ALA-fed leaves synthesized enough PCHLD in the dark preincubation period to form more CHL than controls in a subsequent 2-hr period of low intensity illumination; (b) CHX decreased the rate of CHL formation within 1 1 hr after it was fed to the leaves.AU illuminations were performed with 7 ft-c of tungsten light unless otherwise noted. The effect of the slight v...

Nodule‐specific root proteins – so called nodulins – were identified in root nodules of pea plants by an immunological assay. Nodulin patterns were examined at different stages of nodule development. About 30 nodulins were detectable during development. Some were preferentially synthesized before nitrogen fixation started, whereas the majority were synthesized concomitantly with leghaemoglobin. Some of the nodulins were located within the peribacteroid membrane. Ineffective Rhizobium strains (a natural nod+fix‐ and a pop ‐fix‐) appeared to be useful in studying the expression of nodulin genes. Synthesis of some nodulins was repressed in ineffective root nodules, indicating that nodulins are essential for the establishment of nitrogen fixation. In both types of ineffective root nodules, leghaemoglobin synthesis was not completely repressed. Low amounts of leghaemoglobin were always detected in young ineffective root nodules whereas in old nodules no leghaemoglobin was present.

During odaon of soybean (Glycine max) by Rhizobwum japonicam, varitions

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