遮光對彩葉草葉色及生長之影響

Effects of Shading on Growth and Leaf Color of Coleus

彩葉草之葉色豐富，是常見的花壇植物。遮光會影響生長與葉色；但品種間之反應可能不同。本試驗取五個種子繁殖系品種、五個營養繁殖系品種及十個自選彩葉草雜交後代；盆栽植株於夏季移入溫室內以0%（765μmol•m^(-2)•s^(-1)PPF）、48%（398μmol•m^(-2)•s^(-1)PPF）及67%（252μmol•m^(-2)•s^(-1)PPF）遮光處理，以觀察遮光對生長及葉色之影響。結果種子系品種除'Wizard Pastel'外，皆以67%遮光處理之總葉面積較大。參試營養系之葉長、葉寬及總葉面積亦皆以67%遮光處理者最大。遮光也減少'Black Cloud'以外之各營養系品種之新生葉數。彩葉草'Wizard Pastel'、'Black Cloud'與97-5、97-8及97-2等品種／系之總葉面積與新生葉數於遮光處理間無顯著差異，對光度適應性較廣。雜交後代除了97-4、97-3與97-26外，不遮光處理之新葉數與總葉面積皆最高。67%遮光處理減少所有參試植物之根乾重；但增加葉身之濃綠度。在紅／紫色品種及其雜交後代中，未遮光處理之葉身呈現較多而深之紅紫色。 Solenostemon scutellarioides (L.) Codd, commonly known as coleus, is a popular bedding plant valued notably for its vibrant color foliage. Irradiance may change leaf coloration of coleus cultivars, and thus affect landscape performance. We investigated the differences in growth and leaf color of five seed-propagated cultivars, five vegetatively-propagated cultivars, and ten crossed progeny in response to shading under sumer greenhouse conditions. The magnitude of shading included 0% (765μmol•m^(-2)•s^(-1) PPF), 48% (398μmol•m^(-2)•s^(-1) PPF), and 67% (252μmol•m^(-2)•s^(-1) PPF). All seed-propagated coleus cultivars except 'Wizard Pastel' had larger total leaf areas under 67% shading. All vegetatively-propagated cultivars except 'Black Cloud' received 67% shading had increased leaf length, width, and leaf area but reduced the number of new-grown leaves. Total leaf area and the number of new-grown leaves of 'Wizard Pastel', 'Black Black', 97-5, 97-8, and 97-2 did not differ significantly among the shading treatments. Except 97-9, 97-3, and 97-26, other crossed progeny kept under 0% shading had more new leaves and larger total leaf areas than those kept under 48% or 67% shading. All plants placed under 67% shading had reduced root dry weight and displayed darker green leaves. Red and purple colored cultivars reduced the intensity of these pigments by shading.