Seedlings of the three coniferous species including
Thujopsis dolabrata var.
hondai Makino were raised under weak shade in a nursery in order to examine the photochemical and nonphotochemical dissipations of excited energy at PSII. The dry matter growth 20 weeks after germination was smallest in
T. dolabrata var.
hondai. This was due to the low photosynthetic capacity in addition to the small leaf weight ratio of the seedlings and the large leaf specific weight. The specific ranking of rETR
max (the maximum relative electron transport rate) was different from that of NPQ
max (the maximum of non-photochemical quenching) ;
T. dolabrata var.
hondai was characterized by the high NPQ
max relative to the low rETR
max. A slight depression in
Fv/Fm, (light stress parameter) was recognized only for
Cryptomeria japonica in the cotyledon period. A large depression in
Fv/Fm was observed for
C. japonica and
T. dolabrata var.
hondai in the post-cotyledon period. These depressions in
Fv/Fm seemed to be closely associated with the low levels of rETR
max but may have also been related to the effects of NPQ
max and foliage morphology and architecture. The light responsibility of
T. dolabrata var.
hondai seedlings differed greatly from that of
Pinus densiflora Sieb. et Zucc. and differed significantly from that of
C. japonica.
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