Growth of Chara Hispida: I. Apical Growth and Basal Decay

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Abstract
A comparison is made between seasonal growth rate of C. hispida cuttings and biomass estimates over the depth range 2-16 m in a flooded quarry. C. hispida occurred in a pure stand in water between 6.5 m and 13.5 m deep and was found only once above 5.5 m and never below 14 m during a 2-yr period. Rates of increase in dry weight of cuttings at 14 m were always close to or less than zero, while values for cuttings at 2 m and 4 m were always positive. It is suggested that C. hispida''s absence above 5.5 m is due either to between-species competition or to the lack of a suitable substratum for rhizoid penetration; low photon flux densities are thought to determine the lower depth of colonization. Seasonal growth rates of cuttings in the 6-14 m depth range did not show a correlation with changes in the biomass. C. hispida utilizes a self-pruning mechanism to cope with the high light attenuation within a stand; growth of the apex is balanced by death at the bases of the plant. Other Chara spp. use this stratagem also.