Abstract
Summary Cortaderia pilosa (whitegrass) is a slow growing grass adapted to the cool and moist climate of the Falkland Islands. In well drained, sheltered areas it tends to produce tussock forms whereas on level and poorly drained soils it produces a lax growth habit. Both morphotypes have a similar N-nutrition requirement as well as toleration to waterlogging and anaerobiosis. However, the tussock morphotype appears to be inherently larger and more vigorous than the lax morphotype. The photosynthetic and respiratory characteristics in vivo were measured in leaves of both morphotypes: Fv/Fm = an indicator of maximal quantum yield of PSII photochemistry, net photosynthesis (Pn), photorespiration (PR), dark respiration (DR), the CO 2 compensation concentration(Γ), and content of chlorophylls and carotenoids. Both morphotypes had similar, low values of Fv/Fm in the range 0.64–0.65. The rates of Pn and PR and content of photosynthetic pigments were markedly higher in the tussock than the lax morphotype whereas rates of DR were by about 30% higher in the lax than the tussock morphotype. The ratio of DR/Pn in the tussock and lax morphotypes was 0.14 and 0.27, respectively. Increased DR in the lax morphotype may be a protective mechanism against stress by which respiratory-derived ATP and reductant are provided to continue cell metabolism at a reduced level of photosynthesis. It is concluded that the better growth of tussock than lax morphotype of Cortaderia pilosa can be attributed to its higher rates of net photosynthesis, higher content of photosynthetic pigments and to lower rates of dark respiration.
Published Version
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