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PHOTOACCLIMATION AND GROWTH RATE RESPONSES OF ULVA ROTUNDATA (CHLOROPHYTA) TO INTRADAY VARIATIONS IN GROWTH IRRADIANCE 1
Author(s) -
Henley William J.,
Ramus J.
Publication year - 1989
Publication title -
journal of phycology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.85
H-Index - 127
eISSN - 1529-8817
pISSN - 0022-3646
DOI - 10.1111/j.1529-8817.1989.tb00137.x
Subject(s) - irradiance , photosynthesis , biology , botany , chlorophyta , chlorophyll a , growth rate , algae , steady state (chemistry) , chlorophyll fluorescence , zoology , atmospheric sciences , horticulture , physics , chemistry , geometry , mathematics , quantum mechanics
A vegetative clone of the chlorophyte macroalga Ulva rotundata was maintained in an outdoor continuous flow system under nutrient sufficient conditions and various light regimes. Step changes between 9 and 100% incident irradiance (I o ) were employed to simulate cloud passage. Temporary (1–4 h) midday (I o )perturbations evoked net changes in growth rate (μ) and chlorophyll (chl) content. Under I o alternating at various periodicities from 15 min to 7 h, net μ was the average of the μ under steady state 9 and 100% I o , regardless of periodicity. However, the μ in alternating light was considerably less than μ under steady state 55% I o (≃ 9%+ 100%/2), as expected based on the nonlinear shape of the μ‐I relationship. Unlike μ, chl content depended primarily on the total daily irradiance, probably clue to the slower response of chl compared to photosynthetic rate. On time scales ≥ one day, chl was linearly correlated with light‐regulated daily μ under both steady state and intraday fluctuating irradiance, consistent with photosynthetic feedback regulation of chl concentration.