鹿角蕨孢子繁殖技術之研究

Abstract

水龍骨科(Polypodiaceae)鹿角蕨屬(Platycerium)有18個原種，其雙形態葉片具園藝觀賞價值，唯其繁殖技術尚不完全，研究其促進孢子繁殖效率與孢子形成之方法有助於商業生產模式的建立，亦有機會發展雜交育種技術。 試驗研究11種鹿角蕨屬孢子的萌發適溫為20-30℃，而以萌發速率計算孢子萌發之三基點，最低溫度介於6-11℃，最適溫度為27-30℃，最大溫度則為33-38℃。孢子萌發溫積值以巨大鹿角蕨最高(71.4℃d)，二叉鹿角蕨則最低(26.1℃d)。 強生氏養液EC值在4.0 dS·m-1以下通常不影響鹿角蕨的孢子萌發率，而施用養液會使女王、巨大及亞洲猴腦鹿角蕨的孢子萌發速率略為下降，但會顯著加速象耳鹿角蕨的孢子萌發。養液濃度對配子體假根數影響較小，而細胞數量則會隨養液處理濃度提高而顯著上升。 女王及亞洲猴腦鹿角蕨孢子以1-100 mg·L-1的GA3處理無法誘導於黑暗中萌發，而累積光照1分鐘即可促使萌發。女王鹿角蕨的孢子萌發率在光度高於400 μmol·m-2·s-1 PPFD時會顯著下降，亞洲猴腦鹿角蕨孢子萌發率在500 μmol·m-2·s-1內不具顯著差異。而女王及亞洲猴腦鹿角蕨孢子萌發與配子體生長的最適光度分別為200-300與100-400 μmol·m-2·s-1，且光照時間越長則越有利於配子體的細胞分裂。以5℃貯藏能使鹿角蕨孢子在貯藏6個月後維持較高的萌發率。 女王鹿角蕨的配子體密度每cm2低於10個時有約61%-79%的配子體為雌性，孢子體形成率最高且孢子苗生長最佳。雙性配子體在每cm2低於20個時約占20%-30%，而每 cm2 配子體數介於31-40個時則有高達97%的配子體為雄性，無孢子體形成。配子體以雌性最大，雙性最小，而三種性別之配子體長寬皆會隨著密度上升而下降。配子體每cm2有11-20個處理者每cm2可形成4.2個孢子體，顯著高於其他處理。以1-100 mg·L-1的GA3處理僅能略為提高女王鹿角蕨雙性配子體的比例，無法促進雄性配子體形成。 以0%強生氏養液處理的女王鹿角蕨配子體發育速度慢，且形成近60%的雄性配子體，不利於孢子體形成；以濃度400%處理的孢子體密度較高(每cm2近3個)，但汙染率高。故施用100%養液作為基肥，於原葉體形成時補充100%養液，能維持孢子體形成數量並有效降低汙染損失。女王鹿角蕨孢子撒播後以光度50-300 μmol·m-2·s-1培養，其配子體發育速度無差異。以200及300 μmol·m-2·s-1處理18週後之孢子體形成率較高，每cm2平均能形成3.5-3.8個孢子體。 女王及亞洲猴腦鹿角蕨配子體以日夜溫20/15、25/20、30/25℃處理能形成較高密度的孢子體；二叉鹿角蕨配子體以15/13、20/15、25/20、30/25℃處理的孢子體形成率相似，但以20/15、25/20℃的孢子體密度較高。女王、皇冠、亞洲猴腦、二叉及爪哇鹿角蕨幼孢子體以日夜溫20/15及25/20°C處理的存活率較高，以25/20、30/25℃處理者生長較佳。 取株齡約三年、營養葉長約45 cm之女王鹿角蕨栽培於自然光照人工氣候室五種日/夜溫處理6個月後，所有處理之植株皆未形成孢子葉。以15/13、20/15、25/20及30/25℃處理之營養葉片長寬、葉綠素計SPAD-502讀值與各光系統II參數之差異不顯著。15/13℃處理者之新生葉片數最少、氣孔密度最低且氣孔導度下降；35/30℃處理者葉片黃化且變小而薄，葉片具最低的氣孔導度、光化學焠熄係數與Fv/Fm值(0.65)，而有最高的非光化學焠熄係數。 以遮光0%、62%、72%及81%處理株齡近4年、營養葉長約50 cm的女王鹿角蕨1年，大多於二至四月間萌發孢子葉，孢子葉形成率隨遮光程度提高而上升。以0%遮光處理者具最大的營養葉，但各處理的孢子葉長寬差異不顯著。遮光不影響葉片氣孔密度、長寬與氣孔導度，而營養葉氣孔密度與長度皆大於孢子葉。以72%及81%處理的葉片qP較低，但各處理的PSII實際光化學效率(ΦPSII) (0.72-0.75)與Fv/Fm值(0.76-0.81)皆於正常範圍。而以0-300 mg·L-1的GA3溶液噴施女王鹿角蕨無法促進孢子葉形成。結果顯示女王鹿角蕨的生殖生長主要與自然物候性及植株本身成熟度有關，而遮光有助於孢子葉形成。

The genus Platycerium that is placed in the family Polypodiaceae includes 18 species. The dimorphic fronds are considered with high ornamental value. However, the comprehensive propagation technique is still required. Understanding of the factors that promote spore propagation efficiency and sporulation will help sporeling production and cross breeding. The optimum temperature for spore germination of 11 species of Platycerium was 20-30℃, and the cardinal temperature of spore germination are calculated based on the germination rate. The base temperature was 6-11℃, the optimum temperature was 27-30℃, and the maximum temperature was 33-38°C. The spore germination accumulated thermal time was the highest (71.4℃d) in P. superbum, and the lowest (26.1℃d) in P. madagascariense. The EC value of Johnson’s solution below 4.0 dS·m-1 usually did not affect the spore germination percentage of Platycerium, while the application of nutrient solution slightly decreased the spore germination rate of P. wandae, P. superbum and P. ridleyi, but significantly accelerated the spore germination of P. elephantotis. The concentration of the nutrient solution had little effect on gametophyte rhizoid number, while cell number increased significantly in higher concentration. P. wandae and P. ridleyi spores germination could not be induced by GA3 treatments in the dark, while induced by accumulated light exposure for 1 minute. The spore germination percentage of P. wandae was significantly decreased when light intensity was higher than 400 μmol·m-2·s-1 PPFD, but there was no significant difference in the spore germination percentage of P. ridleyi within 50-500 μmol·m-2·s-1 PPFD. The optimum light intensity for spore germination and gametophyte growth of P. wandae and P. ridleyi were 200-300 and 100-400 μmol·m-2·s-1 PPFD, respectively. Longer light exposure time would promote cell division of gametophytes. Storage at 5℃ could maintained higher germination percentage of Platycerium spores after 6 months. When the gametophyte density of P. wandae was less than 10 per cm2, about 61%-79% of the gametophytes were female, the sporophyte formation rate was the highest and the sporophyte growth was the best. Hermaphroditic gametophytes account for about 20%-30% when density less than 20 per cm2. When the gametophyte density was between 31-40 per cm2, up to 97% of the gametophytes were male, and no sporophyte was formed. The female gametophytes were the largest and the hermaphroditic gametophytes were the smallest. The gametophyte length and width of the three genders would decreased as the density increased. When the gametophyte density was between 11-20 per cm2, 4.2 sporophytes were formed per cm2, which was significantly higher than other treatments. Treatments with 1-100 mg·L-1 of GA3 could only slightly increase the frequency of hermaphrodic gametophytes, but could not promote the formation of male gametophytes. The gametophyte development of P. wandae treated with 0% Johnson's solution was slower, and nearly 60% gametophytes were male, with little sporophytes formation. In the treatment of 400% solution, the sporophyte density was high (nearly 3 per cm2), but the contamination rate was higher. Applying 100% solution as base fertilizer and supplementing 100% solution when prothallus was formed could maintain the number of sporophytes formed and effectively reduce pollution losses. Gametophyte development of P. wandae cultured under 50-300 μmol·m-2·s-1 PPFD was no difference. The sporophyte formation rate was higher after 18 weeks of treatment with 200 and 300 μmol·m-2·s-1 PPFD., formed 3.5-3.8 sporophytes per cm2. The sporophyte densities of P. wandae and P. ridleyi gametophytes treated with day /night temperatures of 20/15, 25/20, and 30/25℃ were higher. The sporophyte formation rate of P. bifurcatum at 15/13, 20/15, 25/20 and 30/25℃ were similar, but the sporophyte density was higher at 20/15 and 25/20℃. The survival rate of P. wandae, P. coronarium, P. ridleyi, P. bifurcatum and P. willinckii young sporophytes at 20/15 and 25/20°C was higher, and those at 25/20 and 30/25°C had better growth. Growth and photosystem Ⅱ of three-year-old P. wandae (sterile frond length 45 cm) were measured with various day/night temperature under natural light phytotrons conditions for 6 months. No plants formed fertile fronds. Results showed that sterile frond length, width, SPAD-502 value and photosystem II parameters did not differ in plants at 15/13, 20/15, 25/20 and 30/25℃. Plants at 15/13℃ produced the fewest frond number, lowest stomatal density and reduced stomatal conductance. In contrast, plants at 35/30℃ had the smallest and thinnest chlorotic fronds, with lowest stomatal conductance, Fv/Fm value (0.65) and photochemical quenching but highest non-photochemical quenching. Nearly 4-year-old P. wandae were treated with shading of 0%, 62%, 72% and 81% for 1 year. Results showed that fertile fronds emerged between February and April, the formation rate increased with the level of shading. Plants under 0% shading had largest sterile fronds, but length and width of fertile fronds did not differ in all treatments. The PSII photochemical efficiency (0.72-0.75) and Fv/Fm value (0.76-0.81) of each treatment were not significantly different, but plants under 72% and 81% shading had lower photochemical quenching. In addition, spraying 0-300 mg·L-1 of GA3 solution could not promote fertile frond formation. In conclusion, the reproductive growth of P. wandae was mainly related to phenology and plant maturity, and shading would increased the formation of fertile fronds.