台灣十九種原生林木種子儲藏行為之比較研究

Abstract

本研究以19種台灣原生林木種子進行發芽與儲藏試驗，以鑑定各種種子的休眠性質與解除方法，並判定各種種子的儲藏行為，不僅為建立這些種子的基本資料，並透過這些結果數據期能建立台灣原生林木種子的儲藏策略模式，並用以修正由Hong and Ellis (1996) 所建構的判斷種子儲藏行為之準則。 結果顯示大頭茶、黃連木、台灣欒樹、破布子、朴樹、紅檜、台灣扁柏、茄苳、台灣油杉、台灣雅楠、長尾柯、蘭嶼木薑子與蘭嶼肉豆蔻等種子不具休眠性，以30/20℃變溫經8~12週後就能發芽完畢。白桕、櫸木及鐵釘樹種子稍具休眠，野鴉椿與鹿皮斑木薑子種子則具深度休眠。 當大頭茶種子乾燥至5.1~9.9% mc、黃連木乾燥至5.4~8.6% mc、台灣欒樹乾燥至5.4~9.7 mc、流蘇種子含水率降低至4.8~7.9%、野鴉椿種子乾燥到4.2~10.9% mc、破布子種子乾燥到4.5~12.7% mc、朴樹種子乾燥到3.8% mc與白桕種子含水率降低至1.8~7.9%儲藏於-20℃經18~24個月後，以及紅檜種子含水率降至4.0~11.7%、台灣扁柏種子含水率降至4.8~10.1%儲藏在-70與-20℃經9年後，以上種子均仍能維持活力，故判定其均屬正儲型。 櫸木、茄苳、鐵釘樹與鹿皮斑木薑子等新鮮成熟種子能耐乾旱，當含水率分別被降至2.1~18.4%、5.3~12.5%、2.0~17.1%與6.0~14.0%後，大部分種子均仍能存活，然上述各級含水率種子均不耐-20℃儲藏，在24個月後發芽率都會顯著下降，因此這些能忍受乾燥卻對零下低溫敏感之種子明顯有別於乾、異儲型，即屬中間型種子。 台灣油杉、台灣雅楠與長尾柯的新鮮成熟種子對乾燥非常敏感，當含水率分別被降至12.0%、11.5%與23.1%時種子就完全喪失活力，且這些種子對零下低溫非常敏感，短時間內就會死亡殆盡，儲藏溫度以4℃稍優於15℃，故判定其屬溫帶異儲型種子。 蘭嶼木薑子與蘭嶼肉豆蔻等大型種子對乾燥極其敏感，當新鮮種子含水率稍降則種子死亡快速，當種子分別乾燥至33.6%與27.0%時則完全喪失活力，且它們對低溫也極其敏感，新鮮種子在4℃濕藏時壽命之維持分別不超過30與7日，故判斷其種子屬於熱帶異儲型。 依據上述與前人研究結果，據以提出儲藏中間型種子的含水率最適界與最適溫度，並修正Hong and Ellis (1996) 所建構的判斷種子儲藏行為之準則。另將種子之儲藏行為概括分為四大類型，各類型種子的適當儲藏條件為： 一、正儲型：在約20℃的環境下儘速將種子含水率乾燥到3~7%，隨即密封置入-20℃環境中以進行長期儲藏，若為10年的中期儲藏則儲存於4℃中即可。 二、中間型： (一)乾質果種子如櫸木、槭樹等，將種子含水率降到8~14%，密封乾藏在約-20~15℃的環境中(含水率與儲藏溫度最適界因種而異)，壽命估計可達3~10年。 (二)肉質果種子如樟屬、釣樟屬等各種中間型種子，以塑膠袋包裝濕藏於4℃為佳，但儲藏期間至少每個月需換氣一次，壽命估計可達1~5年，休眠性愈深的種子壽命愈長。 三、溫帶異儲型：如大部分的樟科、殼斗科種子，以濕藏於4℃為最佳方法，儲藏期間適當的氧氣供給非常重要，故至少每個月需換氣一次，壽命可能達到0.5~3年。 四、熱帶異儲型：無法忍受低溫，且10~15℃就呈敏感，故此類種子難以整粒種子形式來進行儲藏。

The effects of seed moisture content and storage temperature on seed germination were investigated to determine seed dormancy, and seed storage behavior of 19 native tree species of Taiwan in this study. In addition to set up the seed database of these species, these information are useful in layout the storage strategy of Taiwan native tree seeds. Seeds of Gordonia axillaries, Pistacia chinensis, Koelreuteria henryi, Cordia dichotoma, Celtis sinensis,Chamaecyparis formosensis, Chamaecyparis obtusa var. formosana, Bischofia javanica, Keteleeria davidiana var. formosana, Phoebe formosana, Castanopsis cuspidata var. carlesii form. carlesii, Litsea garciae, and Myristica ceylanica var. cagayanensis did not show dormancy. Most seeds could germinate completely in a period of time between 8~12 weeks under alternating temperatures of 30/20℃ with 8 hours of light. Seeds of Sapium discolor, Zelkova serrata and Lindera erythrocarpa exhibited moderate dormancy, whereas seeds of Euscaphis japonica and Litsea coreana showed deep dormancy. Seed germinability of G. axillaries, P. chinensis, K. henryi, C. retusus, E. japonica, C. dichotoma, C. sinensis, and S. discolor could be maintained at -20℃, for at least 18~24 mo at moisture contents of 5.1~9.9%, 5.4~8.6%, 5.4~9.7%, 4.8~7.9%, 4.2~10.9%, 4.5~12.7%, 3.8% and 1.8~7.9% (on FW basis), respectively; and germination of C. formosensis and C. obtusa var. formosana did not decline when seeds were stored at -70℃ and -20℃ for 9 years at moisture contents of 4.0~11.7% and 4.8~10.1%, respectively. These results reveal that above species show orthodox seed storage behavior. Freshly mature seeds of Z. serrata, B. javanica, L. erythrocarpa, and L. coreana showed desiccation tolerance; most seeds survived when they were desiccated to moisture contents of 2.1~18.4%, 5.3~12.5%, 2.0~17.1%, and 6.0~14.0%, respectively. However, viability of these seeds with above moisture contents declined significantly at -20℃ after 24 mo of hermetic storage. These results confirm intermediate storage behavior that is characterized as being tolerant to desiccation but sensitive to freezing temperatures. Freshly mature seeds of K. davidiana var. formosana, P. formosana, and C. cuspidata var. carlesii form. carlesii were sensitive to desiccation and subzero temperature. Seeds of these three species lost their germinability completely when they were dried to moisture contents of 12%, 11.5%, and 23.1%, respectively. They were extremely sensitive to freezing temperatures but could be better maintained at 4℃ than 15℃, and therefore confirm temperate recalcitrant storage behavior. Freshly mature seeds of L. garciae and M. ceylanica var. cagayanensis with large size showed extremely sensitive to desiccation and chilling temperature, and lost viability when were dried to moisture contents of 33.6% and 27.0%, respectively. Maximum longevities of these two species were 30 days and 7 days, respectively, when stored at 4℃, and confirm tropical recalcitrant storage behavior. Based on the above results in conjunction with other references, we propose that the optimum moisture content and temperature for storage of intermediate seeds, and revise the protocol to determine seed storage behavior by Hong and Ellis (1996). We conclude that there are four categories of storage behavior of seed and suggest appropriate environments of storage as follows. 1. Orthodox: reducing seed moisture content to 3~7% at 20℃, then storing hermetically at -20℃ for long term storage or at 4℃ for 10-year medium term storage. 2. Intermediate: (1) reducing seed moisture content of dry fruit (e. g. Zelkova, Acer spp.) to 8~14% and then hermetically storing at -20~15℃. The optimum moisture contents and temperatures for storage are different by species, and the potential longevity is between 3~10 years. (2) storing the seeds of fleshy fruit (e. g. Cinnamomum, Lindera spp.) in plastic bag with moist condition at 4℃ and refreshing the air of container once every month. The potential longevity is between 1~5 years. The seeds with deeper dormancy always have greater longevity. 3. Temperate recalcitrant: most species of Lauraceae and Fagaceae are found in this category. Storing the seeds at 4℃ in moist condition and refreshing the air of container once every month at least. The potential longevity is probably between 0.5~3 years. 4. Tropical recalcitrant: seeds are sensitive to temperatures of 10~15℃. Seeds should not be stored.