本試驗以三種臺灣原生闊葉樹種:樟樹(Cinnamomum camphora Pnesl.)、青剛櫟(Cyclobalanopsis glauca Thunb.)與光臘樹(Fraxinus griffithi Hay.)之苗木為對象,進行光量與光質之馴化處理。光量處理分為5%、25%、50%及100%四種不同相對光量,其中相對光量5%與25%又分為紅光/遠紅光比為0.6及1.3二光質處理。試驗自2002年8月至2003年7月止,在台大農場玻璃溫室進行。實驗期間每月記錄苗木苗高及地徑生長,最終取樣另量測其葉面積及各部位乾重,並於取樣前完成葉綠素濃度及光合作用之測定。 結果顯示:強光抑制樟樹節間發育,高生長以相對光量25%下最佳。青剛櫟及光臘樹節間發育則在相對光量50%下較佳,致高生長最大。光量提高使三樹種之地徑及乾重上升,且地下部生物量之分配比例提高。相對地,對莖、葉部分配比例則減少,惟青剛櫟之莖重率有隨光量上升而增加的趨勢。三樹種之總葉面積及單葉面積皆在輕度至中度遮蔭下最大,強光或重度遮蔭對葉面積生長皆有抑制的效應。光量上升時比葉面積因葉片增厚而下降,葉面積比亦下降。 低R/Fr使樟樹節間抽長,高生長提升。對青剛櫟與光臘樹則使其節間數增加,然在高生長上無顯著效應。苗木外觀與形質上,三樹種中僅樟樹之纖弱指數受光質影響,在R/Fr低時較大,但其S/R率與生物量分配和青剛櫟、光臘樹表現一致,光質效應皆不顯著。 單位乾重及單位面積葉綠素含量在遮蔭下皆有增加的趨勢。在遮蔭下樟樹與青剛櫟之葉綠素a/b比上升。青剛櫟之葉綠素a/b比不受光質影響,樟樹與光臘樹之葉綠素a/b比則在R/Fr下降時上升。 三樹種暗呼吸速率隨光量上升而增加,光補償點亦隨之提高。光臘樹之光量子效益在處理間無顯著差異,樟樹與青剛櫟在強光下馴化者則有較高的光量子效益。最大光合速率以全光馴化者最高,光飽和點光量亦最高,且較遮蔭下的苗木不易受到光抑制或光傷害。光質則對光合作用表現無顯著效應。 整體的表現顯示,樟樹在遮蔭下同時因光量與光質的效應,提高對莖生長的投資,以莖部的徒長得到更多的太陽輻射,在強光下則顯現高生長及葉部生長之抑制。青剛櫟之生長表現多對光質無反應,於低光量對莖部之分配減少,生長停滯,在高光量下則有較佳的生長。光臘樹則在全光或輕度的遮蔭下生長較佳,在較強的遮蔭下,雖對莖部生長分配之比例提高,但其生長仍呈衰弱的情形。
Simulated light treatments were performed on seedlings of 3 native hardwood species, Camphor tree (Cinnamonum camphora), Glaucous oak (Cyclobalanopsis glauca), and Formosan ash (Franxinus griffithii). Six combinations of light treatments included relative light intensity (RLI 100%, 50%, 25%, and 5%) and light quality ( R/Fr=0.6, 1.3). Result showed that high light significantly inhibited internode development of Camphor tree. Height growth of Camphor tree was greatest under 25% RLI, while Glaucous oak and Formosan ash were greatest under full sun light. Of all three species, basal diameter, total biomass and underground biomass allocation were increased as RLI increased, while decrease of leaf and stem mass ratio was observed. Exception occurred on Glaucous oak with an increase in stem mass ratio under higher light. Total leaf area and single leaf area were greatest under medium shade, with suppression of both high light and heavy shade. Specific leaf area was decreased as light intensity was decreased because of leaf thickening, which also resulted in decrease of leaf area ratio. Internode length and height growth of Camphor tree were stimulated by lower R/Fr ratio. Node numbers of Glaucous oak and Formosan ash were greater under lower R/Fr treatment, yet no significant effect were shown on their height growth. Only in Camphor tree that the specific stem length was affected by light quality and was greater under lower R/Fr. S/R ratio of all three species were not significantly affected by light quality. Leaf area and dry weight based Chlorophyll content were increased under shade condition. Chla/b ratio of Camphor tree and Glaucous oak were increased as light decreased. Decrease of R/Fr ratio had no significant effect on Chla/b of Glaucous oak, but had significant effect on those of two other species. Dark respiration rate and light compensation point were lower under shade environment. Different quantum yields of Formosan ash among light treatments were not significant, yet quantum yields of Camphor tree and Glaucous oak were higher under 50% RLI and full sun light than those of lowerer ones. Maximum photosynthetic rate and light saturation point were highest under full sunlight. Light quality had no effect on photosynthetic performance. Camphor tree appeared more investment in stem growth under shade environment to increase the light captured. The effect was caused by both light quality and quantity. High light suppressed height growth and leaf development of Camphor tree. Light quality didn't affect growth performance of Glaucous oak, which was better under sun then deep shade. Formosan ash grew better under light shade. As shade deepen, growth performance of Formosan weaked due to more biomass allocating to stem.
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