經過瓜類育苗、整蔓及施肥、收成的篇章後，我們來看看瓜類作物的留種及種子儲存吧！
After talking about cultivating seedlings, trimming and fertilizing, and harvesting, let us look into seed saving of gourds this time!
葫蘆科的授粉特性 Pollination of Cucurbitacea
葫蘆科瓜類屬於同株異花作物，也就是同一植株裏出現雌花和雄花予以繁殖，是異花授粉的其中一例。很多植物都會演化成異花授粉來維持多樣性，除了葫蘆科的同株異花，早前在我們FACEBOOK和INSTAGRAM提到蘿蔔等十字花科的自交不親和也是其中一個例子。
瓜類的雌雄花分化主要與日照長短有關，日照短有利葫蘆科雌花生長。瓜類需要透過蟲媒授粉，容易出現不同品種互交及混雜，尤其是近親交配，好像冬瓜和節瓜、絲瓜和水瓜。爲了得到純度高的種子，必須進行隔離。
Cucurbitaceae is geitonogamy, meaning that pollen is applied from a flower to another flower on the same plant for propagation. This is one form of cross-pollination, which is developed in many plant species for diversity. Self-incompatability in the brassica family, which was featured in one of our earlier post - is another form.
Flowering of cucurbitaceae is highly affected by sunlight. Shorter length of day actually benefit the flowering of female flowers. Cucurbitaceae depends on insects, in particular bees for pollination. Isolation is needed to avoid inbreeding and to save seeds that are high in purity.
隔離 Isolation
瓜類的隔離主要分爲兩種。其他種植品種距離至少1000米的空間隔離，或以網室進行物理性隔離。種植時確保一定株數以保持群體的基因多樣性，這樣品種特性才容易傳給下一代。瓜類需要大概10-20株。栽種時盡量減少側枝數量，確保養分輸送。
不過，網室内可能會出現日照不足、空氣不流通、氣溫較高的情況，而且需要透過人工授粉才能協助瓜類繁殖。
There are two kinds of isolation. Spatial isolation of keeping a 1000m distance within crops, or physial isolation of setting up nettings. Plant enough to maintain genetic diversity, enabling higher chance for characteristics to be passed onto next generation. It is suggested that 10-20 plants is sufficient for cucurbitaceae. Cut unnecessary vines to concentrate nutrients.
However, netting may decrease exposure to sunlight, worsen ventilation, and highten temperature. It will also require hand pollination.
授粉及篩選 Pollination and Selection
挑選最早開花而健壯的植株，為植株第10-20節位的雌花進行授粉。去除所有畸形果。理論上，人工授粉宜於清晨進行，這時候花粉的發芽力最高。為授粉後的果實套上膠紙牌等記號以作識別，並標示授粉日。
確保植株及果實不帶病，如瓜類的果腐病（Fruit Rot）。如果帶病，不應留種。病害可以通過種子傳播，開花前清除病株。採種子天氣要好，避免下雨和潮濕天氣。
Select early flowering and vigorous plants for seed saving. Hand-pollinate female flowers at 10-20 nodes of the plant and remove deformed fruits. Theoretically, pollination in early morning when flowers are most energetic allows higher germination. Label your pollinated fruits and record the date. Ensure the plant and fruits are not affected by viruses or bacteria such as fruit rot. Any infected plant are not suitble for seed saving, and should be removed before flowering. Choose a sunny day that is not too humid to harvest.
為授粉後的果實套上膠紙牌等記號以作識別，並標示授粉日 / Label your pollinated fruit and record the date
葫蘆科雌花，授粉前花柱為白色 / The style of cucurbitacea female flower remains white before pollination
雄花花藥内藏花粉 / Pollen is hidden within anthers of male flower
採種及保存 Harvesting and Storage
以下是不同品種的種子採收時機：
- 冬瓜、南瓜：留種的瓜需要比最佳食用時機再留於植株上約1-2星期。收果後保存於陰涼處2-4星期等待後熟，但太長時間會容易發芽。
- 青瓜：果實完全成熟變咖啡色後，或變黃時摘下於陰涼處放置約10天。在非金屬容器中清洗種子
- 絲瓜：保留於植株上直至完全乾燥，搖動瓜時會聽到種子晃動的聲音
- 苦瓜：與青瓜相似，果實完全成熟轉爲橙黃色後，或變黃摘下在陰涼處防止約10天。苦瓜種子被一層紅色膠囊狀假種皮包裹。連同膠囊放在容器24小時。不要加水，便容易清洗
- 西瓜：收完後熟7-14天。剖開果實將種子連同瓜肉放於盒内，發酵2-3天清水冲洗去除果膠。
Here are some seed harvesting timing for different species:
- Wax gourd and pumpkin: allow an extra 1-2 weeks maturation. Fruits should be kept in shade 2-4 weeks after harvest for after-ripening, but too long may result in seed germinating. Cut fruit to obtain seeds
- Cucumber: Let the fruit ripen to brown, or harvest fruit that has turned yellow and keep in shade for 10 days. Wash away jelly in a non-metalic container
- Ridge Gourd (Luffa)：Let fruit dried, harvest when you can hear the seeds while shaking the gourd
- Bitter Gourd: Similar to cucumber, let fruit turn orange-yellow, or harvest fruit that has turned yellow and keep in shade for 10 days. Bitter gourd seeds are wrapped in a red jelly-texture aril, leave them in a container and avoid water, wash after 24 hours
- Watermelon: After-ripen for 7-14 days. Leave seeds with flesh in a container to fermentate for 2-3 days, then wash away the jelly
老黃瓜盛載種子 / Harvest seeds in yellow old cucumber
果實完全成熟轉爲橙黃色 / Ripening bitter gourd can be kept in shade for 10 days before obtaining seeds
苦瓜的種子有紅色膠囊包裹 / Red jelly-texture aril coating bitter gourd seeds
大家應該經常聽到種子應該選大而飽滿的。種子的活力、濕度、物理純度及基因純度是選擇種子的標準。這次我們看看種子濕度，讓你掌握留種的基本技術吧！
種子採收後需要洗净風乾。含水量維持於7-8%。那如果我只是爲了興趣留種玩玩，沒有濕度測量儀器怎麽辦？你可以選取一顆種子，較脆和薄的用手折斷，較厚的種子則可以用錘敲碎看看。如果可以輕易斷掉或碎掉，證明種子的乾燥程度合格。
只存放於冷氣倉庫而不控制濕度，種子還是會有在存放期間發芽的風險。James Harrington在1963年提出著名的Harrington經驗法則，種子儲存的相對濕度與溫度(℉)總和，不應該超過100（℃則不應該超過50），當中溫度應為總和的一半以下。家庭儲存種子，最好使用密封錫紙袋，投入乾燥劑，再置於雪櫃。自己花上一個季節留得的種子，記得儲存時要標註品種、採種時間、採種地點，作爲日後的播種記錄啊！
繼續密切留意，我們下一期種子部落的新主題吧！
You'd have heard that high quality seeds should be plump and relatively bigger. Vigor, moisture content, physical purity and genetic purity are all standards for high quality seed. Let us close up to moisture content this time so you know the basic to store the seed you saved!
After drying the harvested seeds, their moisture content should be 7-8%. How do we know without the help of appliances? If it is a thin seed, try break it with your hands. If it is a thick seed, use a hammer. If your seeds can be broken into pieces easily, it is basically dried.
Seeds stored in a refrigerator without humidity contol can still germinate before you want them to. The famous Harrington Rule of Thumb proposed in 1963 suggested that, 'The arithmetic sum of percent relative humidity and the temperature in Fahrenheit should not exceed 100 [50 in celcius], with not more than half of that contributed by temperature'. When we store seeds at home, it is better to keep them in a sealed foil bag with descicant packets, then store in refrigerator. Remember to mark down seed information such as species, time of harvest, spot of harvest for your next sow!
Stay tuned with our SEED BLOG as we open a new topic next time!
Source other than Clover Seed: AVRDC, 種籽保典