採收季節及次級休眠誘導對苦瓜種子活勢之影響

Abstract

苦瓜是台灣重要的蔬菜作物，有良好的營養和藥用價值，台灣本土即可進行採種且有許多優良之F1品種，但苦瓜種子的儲藏性不穩定，有熱季種子儲藏壽命較短的現象。由於全球暖化的影響，持續上升的溫度可能使種子儲藏壽命進一步下降，對產業造成威脅，然而，對苦瓜種子活勢以及儲藏方面的研究有限，其種子儲藏特性也未有定論。本研究目的在建立熱季苦瓜種子的活勢數據，比較熱季和涼季苦瓜成熟種子的品質，以及探討次級休眠誘導之條件和對種子品質的影響。熱季苦瓜 Ⅴ 級種子已達生理成熟，其發芽百分比達到最高，雖然活勢較冷季種子差但已具乾旱耐受性，果實開始轉色為 Ⅴ 級種子開始出現的時機，果實轉色完全時 V 級種子比例達到高峰，可以做為熱季採種指標。熱季苦瓜果實生長速度快，果實由授粉至爆裂的時間較短，種子建立活勢的時間也較短，雖不影響30℃的發芽表現，但在23℃, 約有50%種子的胚根無法突出；老化試驗結果顯示熱季種子活勢較差且容易劣變，顯示儲藏性可能較低。利用加速老化配合胚根突出法，可以有效檢驗苦瓜種子活勢，建議的老化條件為41℃處理3日，胚根突出條件則為23℃處理90小時。苦瓜種子屬於正儲型種子，苦瓜‘月華’種子的次級休眠源自種子之內生性因素，可透過低於-10℃的低溫進行誘導，並且可以40-50℃的處理打破，建議的誘導和打破條件為-20℃處理1日，以及46℃處理10分鐘，次級休眠的誘導和打破並不會對苦瓜種子活勢造成顯著的負面影響，反而可以提升發芽整齊度，若是處在休眠狀態的種子具有較佳的耐儲藏性，則有望解決熱季苦瓜種子儲藏性差的問題、以及未來苦瓜種子產業可能面臨之威脅。

Bitter gourd is an important vegetable crop in Taiwan, with good nutritional and medicinal value. Taiwan has many excellent F1 varieties that can be locally grown, however, in the context of business related to bitter gourd varieties, the storage stability of bitter gourd seeds often exhibits seasonally unstable characteristics, especially hot season seeds showing a much shorter storage life. Due to the ongoing effects of global warming, the gradually increasing temperature might further decrease the storage time of bitter gourd seeds, posing a future threat to the bitter gourd seed industry. However, there is limited research on seed vigor and storage-related aspects, and the storage characteristics of bitter gourd seeds remain inconclusive. This experiment aims to build seed vigor data along the developing process of hot season gourds, compare the seed vigor of the mature seeds of hot and cold season gourds by accelerated aging method and investigate the conditions for inducing secondary dormancy and their effects on seed quality. Level V seeds of hot season bitter gourds have reached physiological maturity, with the highest germination percentage. Although their vigor is lower than that of cool season seeds, they already exhibit desiccation tolerance. The peak proportion of level V seeds coincides with the complete color change of the fruit, indicating that this can be used as an indicator for seed collection in hot season. Since bitter gourd fruits grow faster in hot season, the time for establishing seed vigor is shorter, although it didn’t affect germination performance at 30℃, 50% of the seeds were not able to protrude their radical root at 23℃. Accelerated aging tests show that hot season seeds have lower vigor and are more prone to deterioration, which affects their storage. In addition, using accelerated aging combined with the radicle emergence test can effectively test the vigor of bitter gourd seeds, the recommended condition is 41℃ for 3 days for accelerated aging and 23℃ for 90 hours for radical emergence test. Bitter gourds seeds are orthodox seeds. The secondary dormancy of bitter gourd 'Yue hua' seeds originates from endogenous factors and can be induced by temperature lower than -10°C, which can then be broken by treatments at 40-50°C, the recommended condition for secondary formancy induction and breaking is -20°C 1 day and 46°C 10 min, respectively. The sequence of induction and broken of secondary dormancy in bitter gourd seeds do not significantly negatively affect the vigor of bitter melon seeds; instead, they can improve germination uniformity. If dormancy seeds have better storability, it may help solve the problem of poor longevity of hot season bitter gourd seeds and the potential threats to the bitter gourd seed industry in the future.