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UNCOUPLING OF VARIOUS MEASURES OF GROWTH IN ULVA ROTUXDATA (CHLOROPHYTA) FOLLOWING A LARGE DECREASE IN IRRADIANCE 1
Author(s) -
Henley William J.
Publication year - 1990
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.0022-3646.1990.00206.x
Subject(s) - biology , irradiance , chlorophyta , photosynthesis , botany , algae , growth rate , dry weight , zoology , limiting , horticulture , physics , mechanical engineering , geometry , mathematics , quantum mechanics , engineering
A vegetative clone of the chlorophyte macroalga Ulva rotundata Blid. was maintained in an outdoor continuous flow system and subjected to a large decrease in irradiance. Specific growth rates based on changes in fresh (μ FW ) and dry weight (μ DW ) and surface area (μ SA ) were determined using precut disks over the 24 h following a post‐sunset transfer from full sunlight (100% I 0 ) to 9% I 0 All three measures of growth rate were approximately equivalent for untransferred control plants at either limiting (9%) or saturating (100%)I 0 . Transferred disks exhibited μ FW and μ SA which were slightly lower than 100%I 0 controls and much higher than 9% I 0 controls; μ DW was nearly identical for transferred disks and 9% I 0 controls. Cell size was unchanged following transfer, indicating that surface area changes reflected a proportional increase in cell number. Cell division therefore continued at a high rate for one day following transfer of U. rotundata to irradiances which are subsaturating for photosynthesis (indicated by μ Dw ). Starch reserves were largely depleted, and the C/N ratio decreased during this period.