COMPARATIVE STUDIES OF PLANT GROWTH AND DISTRIBUTION IN RELATION TO WATERLOGGING

XII. GROWTH, PHOTOSYNTHETIC CAPACITY AND METAL ION UPTAKE IN SALIX CAPREA AND S. CINEREA SSP. OLEIFOLIA

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Summary

Rooted cuttings of Salix caprea L. and -S. cinerea ssp. oleifolia (Macreight) growing in soil were exposed to (a) intermittent, (b) partial and (c) complete waterlogging of the soil. Measurements of growth and other characteristics were compared with unflooded controls. Both species were harmed by waterlogging but S. caprea was more sensitive than 5. cinerea as shown by the greater reduction of height, internode number, dry weight of root, stem and leaf, specific leaf area and leaf area per plant. The waterlogging treatments did not differ amongst themselves in the degree of inhibition of growth which they caused. A single fully waterlogged treatment would thus have been quite adequate in screening for tolerance.

The reduction in specific leaf area of S. caprea was probably mediated by reduced turgidity and failure of leaf tissue to expand fully. Leaf iron content increased in both species but less so in S. cinerea, which is able to immobilize more iron in, or on, its roots. 5. caprea leaves contained over 2000 μg g−1 iron, a concentration recorded as toxic in other plants; these leaves became brittle and some lower leaves were shed. Root iron content increased more in S. cinerea than in S. caprea, and this was accompanied by an increase in phosphorus content. Chlorophyll and magnesium content of leaves was significantly reduced in S caprea but not in S. cinerea. Photosynthetic potential was reduced in S. caprea but not in S. cinerea; this was probably unrelated to stomatal control of CO2 uptake. S. cinerea produced adventitious roots at the surface of flooded soil and when cuttings were immersed in water; S. caprea did not. These observations are compatible with the ecology of the two species, S. caprea normally inhabiting better drained soils than 51. cinerea.

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