The dependence of the nitrogen fixing system in the root nodules of pea plants (Pisum sativum) L. cv. Torsdag II) on light induced reactions was studied. The pots of the inoculated pea plants, after the nolules had fixed nitrogen for a fornight, were transferred to a dark room. The control plants were kept under normal lighting conditions. The decay of leghemoglobin was measured after photosynthesis had ceased. In the dark the red nodules turned green in three days, when about half of the haem had been broken down. The plants in normal lighting conditions had maintained the red nodules. The appearence of leghemoglobin and bacteroids was simultaneouos. In normal lighting conditions the number of bacteroids was about 1.6 × 108 per g fresh nodules. The appearance of leghemoglobin and bacteroids was simultaneous. In normal lighting conditons the number of bacteroids was bout 1.6 × 108 per g fresh nodules. At the same time as the nodules turned green in the dark most of the bacteroids disappeared and the number of rod‐shaped bacteria increased. After five days int the dark thenumber of bacteria of the green nodules was 2.2 × 108 per g fresh nodules. A large increase of of bacteria in the nodules is one of the results after the termination of effective symbiosis. Quantitative estimations were made with an automatic amino acid analysator of the amino acid composition in the root nodules of pea plants grown in the light and of pea plants grown in the dark. Altogether 27 amino acids and amides and 3 unknown ninhydrin positive compounds were found in the free amino acid fraction. In the red N‐fixing nodules asparagine, the amide of aspartic acid, was the most prominent (more than 50 per cent of the total amino acid fraction), indicating the energy charge of the nitrogen fixation. 5 days in the dark affected the proportions of the amino acids as follows. Asparagine, homoserine, γ‐aminobutyric acid and ethanolamine were decreased and the most of the others increased. In the hydrolysate of the non‐soluble protein fraction 25 amino acids could be detected. The proportions of the amino acids in the root nodules of light‐grown and dark‐grown pea plants were very similar. Hydroxyproline and α, γ‐diaminopimelic acid (DAP) were found in these fraction. Most of the DAP was contained in the peptide fraction. Also hydroxyproline was found to a small extent. It was assumed that the amino acids in this fraction were derived from the peptides of both plant cells and rhizobia.

Ttie removat of the apical buds from tlie lop of inoculated pea ptants before ftowering caused the axillary buds of the stem leaves to develop and thus further to branch. The vegetative growth of the test plants continued to be luxuiijint wben litooming was delayed. Wtiite ttie control ptants formed seed.s and ripi-ned. tlie vegetative growth of the stem of Itie test ptants increased at nio.st eigtit-foUt during Ihe same time. A new, additionat red part grew at the same time in the root nodules, which had already partly become green. The new red part branched later so that the imusuatty large nodules appeared quite odd. The weight of the tiranehed, large nodules had at the same time increased on the average six-fold and the vegetatively grown test plants synthesized even eight times more nitrogen than did the control plants. The eoncentration of tegbacmoglobin in tbe nodules formed by tlie bacterial strain u.sed in tbe experiment was not inereased, but the absolute amount of the pigment was raised six-fold as a result of the increased nodule mass. While the vegetative growth was going on, oxidation of the tegliaemoglobin was delayed.Analyses of nitrogen and amino acids were made for both test and control planls. The totat length of the branches in the largest test plant was 32 m compared wUti the nnbranched control plant which wa.s 1.30 m.

Observations were made on the content of α-aminoadipic acid and α-aminophimelic acid (DAP) in pea plants, nodules and Rhizobium leguminosarum, strain HT3. The preparations were purified by ion exchange chromatography, Qualitative analyses were made by paper chromatography, and quantitative analyses by means of an automatic amino acid analysator. In the whole plant and seeds the content of α-aminoadipic acid soluble in 70% ethanol varied between 10 and 80 μg/g dry weight. The shoot and red nitrogen fixing nodules contained more of this acid than roots and green inactive nodules. In the insoluble fraction of the shoot its concentration was 0.4-0.6 mg/g dry weight. α-Aminoadipic acid was not found in free living rhizobia, which again contained a considerable amount of α-aiaminopimelic acid, about 0.5 mg/g dry weight. The synthesis of DAP was intensive also in root nodules. In red nodules, which fixed molecular nitrogen, the content of DAP was 2.1 mg/g dry weight and in green inactive nodules 1.3 mg/g dry weight. It was shown that in the nodules DAP is closely connected with cell wall peptides of bacteroids. DAP could not be found in pea plants outside the nodules.

Two pea (Pisum sativum L.) cultivars and a kidney bean (Phaseolus vulgaris L.) cultivars were grown in water cultures at different diurnal temperatures (15, 20, 24, 27, 30°C) or at 10°C night temperature combined with various day temperatures (20, 24, 27, 33 or 35°C) in the root medium. The inoculated plants were, more sensitive to the extreme temperatures than the plants supplied with combined nitrogen (KNO3). The middle‐European pea cv. Violetta was adapted to somewhat higher root temperatures than the northern one cv. Torsdag II, the latter showing better growth at lower temperatures, when the plants were inoculated with the same Finnish Rhizobinm strain (HA1). Especially at optimum day temperatures the nitrogen fixation and consequently the dry weights of the inoculated plants were greatly increased when the night temperature was lowered. The optimum temperature for the growth of free‐living Rhizobium strains (HA1 and H43) for peus was found to be 25°C and that of a strain (P103) for beans somewhat higher. Effective nitrogen fixation by nodulated legumes without a supply of combined nitrogen is achieved only when the optimum temperature range for root function is very close to the optimum for the rhizobia.

On the mycelial growth of the lorel or false morel, Gyromitra esculenta (Pers.) Fr.ILMA ROPONEN and MATTI KREULA ROPONEN, I . A KREULA, M. 1978: On the mycelial growth of the torel or false morel, Gyromitra escultenta (Pers.) Fr. -Karstenia 18 (suppl.).The growth factors of lore I mycelia were investigated in solid and I iquid media. The mycelial strains used in the experiments were isolated by germinating spores of lore Is in Petri dishes on nutr i ant agar. The strains i so I a ted were stored in the co I d in test tubes as pure cultures, and propagated vegetatively by Inoculation. The results showed that the production of spawn is pass i b I e in axen 1 c substrates. This method of cuI t i vat ion needs a ·high degree of sanitation . Spawn growth is at a maxi mum after 3-4 weeks, when the substrate i s fully covered with the mycelium.The pH range 4-7 was observed to be fabourable for the growth of the myce l ia tested . The mycelia grew vigorously when formic acid was added to a concentration of 0.01-0.1 per cent in the substrate, but growth was inhibited when the concentratIon was 0. 2 per cen. or more. The effect of temperature on mycelial growth was tested at +5°, 10°, 15°, 20° and 30° C; optimum growth was obtained at 10-25° C. The mycelia were very sensitive to elev at=~b;~fa~~~centratlons, and effective aeration and shaking were needed for growth in 1 iquid Waste materials from the prepared pulp industry containing hemicel tutose and t ignin appear to be su itab le for the cultivation of lore I mycelia after the addition of a small amount of urea.