SUMMARYRooted 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 unfiooded controls. Both species were harmed by waterlogging but 5. caprea was more sensitive than S. 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 [ig g'^ 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 5. 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 5". 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 COg uptake. S. cinerea produced adventitious roots at the surface of flooded soil and when cuttings were immersed in water; 5. caprea did not. These observations are compatible with the ecology of the two species, S. caprea normally inhabiting better drained soils than 5. cinerea.
Summary
Rooted cuttings of Salix caprea and of S. cinerea ssp. oleifolia were supplied with 0 to 320 mg Fe2+ dm3 as sulphate dissolved in nutrient solution either at a constant concentration or supplied incrementally. Photosynthesis and respiration of the treated plants was monitored by infrared gas analysis for periods of 4 to 7 d.
Control shoots, in air‐bubbled or nitrogen‐bubbled solutions, maintained constant rates of photosynthesis and dark respiration during the experimental period. S. cinerea was unaffected by a constant concentration of 160 mg Fe2+dm3 or incremental additions reaching 320 mg Fe2+ dm−3. S. caprea was unaffected by 10 mg Fe2+ dm3, but a constant concentration of 40 mg Fe2+ dm3 or incremental additions reaching 40 mg Fe2+ dm3 caused almost total inhibition of photosynthesis and considerable reduction of respiration.
Repeating these experiments using cuttings with excised roots increased the sensitivity of both species so that, even in S. cinerea, 10 mg Fe2+ dm3 was inhibitory to photosynthesis.
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