부산대학교 도서관

Since spring ephemerals are credited to be all “sun” species with unusually elevate photosynthesis, in contrast to shade-tolerant trees and understory geophytes with a long aboveground cycle, we examined the photosynthetic efficiency of 6 woody species, 9 long-cycle geophytes, and 8 spring ephemeral geophytes using blue flashes of increasing energy with the Imaging PAM fluorometer. Several parameters were obtained: quantum yield of electron transport (ΦETR) or of PSII (ΦPSII), maximum measured photosynthesis rate (ETR hv ), maximum extrapolated rate of photosynthesis (ETR em ), half-saturating photon flux density (K PAR ), and in some cases photochemical (qP) and non-photochemical quenching (NPQ). Results confirm the ecological consistency of the three plant groups, with internal differences. Woody species have low ETR em and K PAR values with good ΦETR; long-cycle herbs have low ETR em and ΦETR and moderate K PAR values; spring ephemerals have elevate ΦETR, ETR em and K PAR values. The mean ETR em of ephemerals of 91 μmol m −2 s −1 exceeds that of long-cycle herbs 2.9-fold and woody species 4.8-fold, and corresponds to 19 μmol CO 2 m −2 s −1 by assuming an ETR/ΦCO 2 ratio of 4.7. Highest photosynthesis rates and K PAR were exhibited by five ephemerals ( Eranthis, Erythronium, Narcissus, Scilla, Tulipa ) with peak ETR em values equivalent to ∼40 μmol CO 2 m −2 s −1 or ∼60 μmol CO 2 (g Chl) −1 s −1 (“sun” species). According to a new, fluorescence based heliophily index, all trees and five long-cycle herbs were definitely “shade” species, while four long-cycle herbs and three ephemerals were intermediate shade-tolerant. [ABSTRACT FROM AUTHOR]