Respiratory capacity, nitrogenase activity and structural changes of Frankia, in symbiosis with Alnus incana, in response to prolonged darkness

• Published in: Planta 1990-01, Vol.182 (4), p.617-625
• Main Authors: Vikman, P.-A. (Umea Univ. (Sweden). Dept. of Plant Physiology), Lundquist, P.-O, Huss-Danell, K
• Format: Article
• Language: English
• Subjects: ACTIVIDAD ENZIMATICA; ACTIVITE ENZYMATIQUE; Agronomy. Soil science and plant productions; Alnus; ALNUS INCANA; Atmung; Biological and medical sciences; CELL STRUCTURE; Cell walls; Cytoplasm; DARKNESS; Dunkelheit; ECHANGE GAZEUX; Enzymaktivitaet; ENZYMIC ACTIVITY; ESTRUCTURA CELULAR; FRANKIA; Fundamental and applied biological sciences. Psychology; GAS EXCHANGE; Hyphae; INTERCAMBIO DE GASES; Knoellchen; Nitrogen; NITROGENASA; NITROGENASE; NODOSITE RACINAIRE; Nodules; NUDOSIDADES RADICULARES; OBSCURIDAD; OBSCURITE; Parasitism and symbiosis; Plant physiology and development; Plants; Respiration; ROOT NODULES; Starches; STRUCTURE CELLULAIRE; Ultrastruktur; Wurzel
• ISSN: 0032-0935; 1432-2048
• DOI: 10.1007/BF02341040

Plants of Alnus incana (L.) Moench in symbiosis with a local source of Frankia were exposed to prolonged darkness under controlled climate conditions. Frankia vesicle clusters were prepared from the root nodules, and the condition of Frankia was measured as respiratory capacity by supplying the preparation with saturating amounts of four different substrates. During darkness, nitrogenase (EC 1.7.99.2) activity decreased in intact plants and in the vesicle-cluster preparations. The respiratory capacity of Frankia also decreased. After 4 d in darkness most respiration was lost, though all nitrogenase activity was already lost after 3 d. When the dark treatment was ended after 2 d and normal light/dark conditions restored, nitrogenase activity immediately started to recover. The respiratory capacity continued to decrease and no recovery was observed until the third day after the end of the dark treatment. Whole-plant nitrogenase activity slowly increased at a rate similar to the rate of increase observed in untreated plants. Transmission electron micrographs of the root nodules showed that the cytoplasm of infected host cells and the cells of Frankia were structurally degraded in response to dark treatment, while young vesicles were frequent during recovery. Growth and differentiation of Frankia cells were apparently important for recovery of the enzyme activities studied.