Lichen Physiology Research Articles

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Articles published on Lichen Physiology

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Studies in the Physiology of Lichens

The medulla of Peltigera discs can be separated by dissection from the overlying region which comprises the algal layer and upper cortex. In most cases, dissection has no marked effect upon the isolated tissue zones, so that a comparison of them gives a good approximate indication of the relative behaviour of the corresponding regions of the intact thallus. The behaviour of the medulla, entirely fungal in composition, gives some indication of the physiology of the lichen fungus. The algal region has a greater respiration rate and nitrogen content than the medulla, and it absorbs more glucose, asparagine, phosphate, and ammonia than the medulla. Compared to the medulla, the algal region absorbs more glucose than asparagine and this is attributed to a marked preference for glucose on the part of the algal cells. The medulla has a greater water content than the algal region, and may function as a water reservoir.

Annals of Botany

Apr 1, 1960
D C Smith

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Studies in the Physiology of Lichens: With two Figures in the Text

Discs cut from the thallus of the lichen Peltigera polydactyla contain relatively large amounts of ammonia nitrogen and small amounts of amide nitrogen. During starvation in the dark the amounts of ammonia and amide nitrogen remain unchanged, but the amount of amino-nitrogen increases. Absorption of ammonia results in increases in the amounts of ammonia and amino-nitrogen in the discs, but not in the amount of amide nitrogen. It is therefore concluded that amides do not have an important quantitative role in the nitrogen metabolism of the discs. Ammonia absorption is stimulated by addition of glucose to the medium, but the very slow rate of protein synthesis is only slightly increased by glucose. The rate of nitrate absorption is much slower than that of ammonia absorption. The ecological implications of the results are discussed, and existing knowledge of the nitrogen metabolism of lichens is reviewed.