覆盆子在亞熱帶氣候的產期調節與空心莓亞屬植物高溫光合生理

Abstract

覆盆子(Rubus idaeus L.)為源自於溫帶地區的多年生小果類作物，近年來國內鮮果需求快速成長，多由美國空運進口供應。臺灣等亞熱帶氣候區在以往因為夏季氣溫過高與冬季低溫不足，並不適合傳統二年生枝條結果型(floricane-fruiting)品種的生產，然而當年生枝條結果型品種(primocane-fruiting )的普及化，提供了覆盆子在亞熱帶地區生產的契機。本論文嘗試利用產期調節方式解決覆盆子在亞熱帶種植時，當年生枝條開花節位數減少使得產量低落的問題，並探討臺灣原生空心莓亞屬植物與覆盆子在夏季高溫下光合作用差異的生理機制，提供未來耐熱育種篩選與栽培參考。 本論文第二章之產期調節試驗於2016年10月至2017年2月進行，嘗試利用枝條彎曲及暗中斷處理，誘導溫室內之覆盆子‘Summer Festival’植株當年生枝條之低節位萌芽與二次採收，結果顯示兩種處理方式皆無顯著效果，各處理組內標準差大。所有處理之萌芽皆集中於當年生枝條第20-40節位，開花數量亦最多。試驗期間因溫室相對濕度過高，導致授粉不良與真菌性病害嚴重等問題，是未來在亞熱帶環境中之溫室生產覆盆子必需要克服之處。 本文第三章之空心莓亞屬光合作用生理試驗於2017年7月進行，比較溫帶覆盆子及三種原生於台灣亞熱帶平地的空心莓亞屬植物，刺莓(R. rosifolius)、薄瓣懸鉤子(R. croceacanthus)與愷葉懸鉤子(R. fraxinifolius)之光合耐熱生理。試驗以不同溫度(25、30、35℃)環境，測量葉片氣體交換與葉綠素螢光之光反應曲線及二氧化碳反應曲線(A/Ci curve)後，利用FvCB光合生化模型，進行參數擬合，並以數值積分法量化各參數對於淨光合作用速率變化的貢獻程度。在35℃PPFD=1200 μmol·m-2·s-1下，覆盆子的淨光合作用速率最低，且與其他三種原生種差異最大。以FvCB參數進行量化後可得知光合生理之擴散性因子是造成此差異的主要原因，氣孔導度與葉肉細胞導度分別佔總差異一半的貢獻度；生化因子如最大羧化速率與最大電子傳遞速率在所測試的4個物種中，皆隨溫度上升而提高，對物種間高溫下淨光合作用的差異影響不明顯。另由35℃下，葉面溫度與氣溫之差值，也顯示高溫下原生種具有較覆盆子佳的葉片蒸散散熱機制。

The red raspberry (Rubus idaeus L.) is a perennial berry crop originated in the temperate area. In recent years, the demand for fresh raspberry has been increasing in Taiwan and mostly supplied by import products from the USA. Traditional florican-fruiting raspberry cultivars are difficult to grow in the subtropical climate due to heat stress in summer and lack of chilling in winter. However, the new primocane-fruiting cultivars has brought up the possibility to produce raspberries in the warm climate. In this thesis, scheduling techniques to increase the number of flowering laterals on primocanes were tested. In addition, photosynthetic heat tolerance mechanisms of raspberries were investigated by comparing a primocane-fruting cultivar with three relative subtropical species native to low land Taiwan. In chapter two, a scheduling production trial was conducted from October 2016 to February 2017. Shoot bending and night breaking treatments to induce lateral shoots on primocanes and winter harvest were tested in raspberry ‘Summer Festival’ grown in a greenhouse in Taipei. The results showed that neither treatments promoted flowering or lateral development. Most laterals were emerged from 20th -40th node on the primocanes and had the highest flower number per lateral. During the experiment period, the high relative humidity in the greenhouse resulted in poor pollination and servere fungus disease. In chapter three, photosynthesis of the raspberry and three native subtropical species in the same subgenus Idaeobatus were evaluated in July 2017. Gas exchange and chlorophyll fluorescence were simultaneously measured at 25, 30, or 35℃. Light response curves and CO2 response (A/Ci) curves were obtained and key photosynthetic variables were fitted with a modified FvCB model. Differences in net assimilation rate among different species and environmental factors were partitioned into the correspondence of each variable by a numerical integration method. At 35℃under PPFD=1200 μmol·m-2·s-1, the raspberry had the lowest net assimilation rate. The results from partitioning indicated that diffusional factors in the FvCB model were the main contributor to the differences, and stomatal conductance and mesophyll conductance each contributed about 50% of the total difference. Biochemical factors such as the maximum value of carboxylation and electron transportation rate increased in all species as the temperature increased and their contributions to net assimilation differences were little. Temperature differences between leaf surface and the air showed that the native species had a more efficient transpiration cooling mechanism at 35℃ than the raspberry.