氣溫與根溫對開運竹生長與發根之影響

Effects of Air and Root Temperatures on Growth and Rooting of Dracaena sanderiana 'Virens'

本研究探討氣溫與根溫對開運竹發根與生長之影響。將開運竹植株移入人工氣候室，不同日／夜溫處理3個月後，枝梢長度與葉片生長均以25／20℃處理者最佳，而低溫15／13℃處理者最差。高溫35／30℃處理者不利枝梢生長與葉乾重累積。將植株去頂後5週，以35／30℃、30／25℃與25／20℃處理者皆萌發側芽，但20／15℃與15／13℃處理者未萌發。冬季種植之莖幹插穗，底部加熱至25℃或29℃者，經2週後開始發根；而無底部加熱之對照組（根溫18℃）則至6週後開始發根。經處理10週後，以25℃與29℃根溫處理之根乾重、根數與根長均較對照組多，且莖幹之第3與第4節的側芽多可萌發，但對照組僅於第1與第2節萌發側芽。冬季不增加氣溫而僅增加根溫至25℃處理4至6週，可使開運竹莖幹插穗有較佳之發根與萌芽率。 Effects of air and root temperatures on rooting and growth were studied in Dracaena sanderiana 'Virens'. Plants were moved to phytotrons with different day/night temperatures for three months. Maximum shoot length and leaf growth were recorded in plants under 25/20℃, while minimum leaf number and leaf chlorosis was found in plants under 15/13℃. The high temperature of 35/30℃ treatment decreased shoot length and leaf dry weight. Lateral buds sprouted in plants with decapitated shoots under higher temperatures of 35/30℃, 30/25℃or 25/20℃ for five weeks, while no lateral bud outgrowth was visible in those under 20/15 or 15/13℃. In natural winter greenhouse conditions, rooting started in cane cuttings with bottom heat to 25 or 29℃ after two weeks, as compared to rooting with the unheated control (18℃ root temperature) after six weeks. Cane cuttings had more root dry weight, root number and root length in the 25℃ or 29℃ root temperature treatments than the unheated control. The 25℃ or 29℃ root temperatures could trigger lower lateral buds outgrowth (3 to 4 from top), as compared to only lateral buds 1 to 2 outgrowth in cuttings without bottom heat. Root zone heating at 25℃ for four to six weeks resulted in higher rooting and shoot sprouting than those at 29℃ or unheated control and would allow growers to reduce fuel costs by heating the greenhouse air volume.