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Light and pressure in two freshwater lakes and their influence on the growth, morphology and depth limits of Hippuris vulgaris
Author(s) -
BODKIN P.C.,
POSLUSZNYand U.,
DALE H. M.
Publication year - 1980
Publication title -
freshwater biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.297
H-Index - 156
eISSN - 1365-2427
pISSN - 0046-5070
DOI - 10.1111/j.1365-2427.1980.tb01230.x
Subject(s) - shoot , primordium , photosynthetically active radiation , botany , biology , horticulture , photosynthesis , biochemistry , gene
SUMMARY. Hippuris vulgaris was found growing down to a depth of 6 m in two clear‐water lakes. Mean summer water temperatures of the epilimnia were 15–18°C. Midsummer photosynthetically available radiation, (PAR 400–700 nm) at 6 m was 100 μeinsteins m −2 s −1 . In the laboratory, shoots of H. vulgaris continued to elongate at temperatures of 15 and 20°C and at pressures of 1.0, 1.8 and 2.3 atm. (corresponding to 0 m, 8.0 m and 13.3 m depths of water, respectively) providing PAR was kept above 100 °E m −2 s −1 . Leaf primordia were initiated further from the apex in shoots grown under a pressure of 2.3 atm., but the site of initiation is not critical for the subsequent growth of leaves in H. vulgaris . Lacunae in shoots grown under a pressure of 2.3 atm. were also larger than those in control shoots, implying that pressure does not constrict air spaces. Root growth is not inhibited by a pressure of 2.3 atm. Field measurements and laboratory experiments indicate that in warm water, PAR is the environmental factor most likely to control the depth limits of H. vulgaris in the field.