Influence of environmental factors and exogenous nitrogen on nitrogen fixation by intact thallus and excised cephalodia of Peltigera aphthosa

Ngerebara Nn Ngerebara Nn,Amadi Lo Amadi Lo,Ekiyor Ht Ekiyor Ht

doi:10.30574/gscbps.2020.13.1.0313

Abstract

The present study investigates the effects of various abiotic environmental factors: air humidity, moisture content, oxygen and exogenously supplied nitrogen on acetylene reduction by intact thallus and excised cephalodia of Peltgera aphthosa. Intact thallus and excised cephalodia of Peltigera aphthosa were incubated at various conditions of air humidity, moisture contents, oxygen tensions, and addition of exogenous nitrogen, and comparative nitrogen fixation by the intact thallus and excised cephalodia was used as a method for assessment. Acetylene reduction (nitrogen fixation) was enhanced at conditions of lowered oxygen tension and at initial addition of nitrogen to the medium. However, prolonged incubation of Peltigera aphthosa in the medium with combined nitrogen addition resulted in fluctuation of nitrogenase synthesis. Acetylene reduction rates were stimulated in an atmosphere of 100% relative humidity (RH) and moisture content range of 570-620% of dry weight of Peltigera aphthosa. The decrease of nitrogenase activity measurable by acetylene reduction of thallus after prolonged incubation in the medium with combined nitrogen addition shows susceptibility of the symbiosis (lichen) since the thallus showed signs of disintegration at this time. Furthermore, air humidity and moisture content of the thallus influenced nitrogenase synthesis of Peltigera aphthosa considerably on separation of cephalodia such approach decreased nitrogenase activity and also elicited differences in their response to the various treatments. Applicability of this technology would enhance plant sustainability and yield in agricultural farms.

Highlights

Knowledge of nitrogen fixation by blue-green algae has increased substantially within resent years as new groups of nitrogen-fixing algae have been discovered; detailed physiological and biochemical studies on the inter-relations of metabolic processes such as nitrogen-fixation, photosynthesis and respiration have been carried out as well as the ecological importance of the group has been recognized and confirmed [1,2,3,4,5,6,7]
In parts of the subarctic tundra of Sweden, species of Nephroma, Peltigera and Stereocaulon cover ground completely because of their ecological importance [13]. This present study presents data on effects of combined nitrogen addition, air humidity, moisture content and oxygen tension on acetylene reduction by Peltigera aphthosa subjected to laboratory investigation
Reduction of acetylene by the separated cephalodia and absence of such activity in the lichen thallus without cephalodia indicates that the bluegreen phycobiont is the site of nitrogen fixation, which is in agreement with experiment using 15N [15]

Summary

Introduction

Knowledge of nitrogen fixation by blue-green algae has increased substantially within resent years as new groups of nitrogen-fixing algae have been discovered; detailed physiological and biochemical studies on the inter-relations of metabolic processes such as nitrogen-fixation, photosynthesis and respiration have been carried out as well as the ecological importance of the group has been recognized and confirmed [1,2,3,4,5,6,7]. The ecological significant of nitrogen fixation by lichen has only recently been paid greater attention in nitrogen deficient arctic tundra where these organisms are very abundant. At the tundra nitrogen fixation by Stereocaulon and Peltigera species are considered to be of particular importance in the nitrogen budget [9,10].

Methods

Results

Conclusion