辣椒為何有些不辣?

資料來源
網址

Chillies come in many degrees of heat, from the sweet painless bell peppers to the “Trinidad Scorpion Butch T pepper”, a superlatively hot chili that needs to be handled with gloves. A less dramatic range also exists in the wild: some chillies are hot, and others are not. In supermarkets, the spectrum of heat is the result of clever breeding. It the wild, it’s due to a tension between two threats: drought and disease.
辣椒是個很神奇的食物，它有不一樣的辛辣度。從不辣的甜椒到需要戴手套才能處理的"Trinidad Scorpion Butch T pepper" ,顧名思義，如果不戴手套處理，那辛辣的痛覺就像被蝎子刺到一般。
野生的辣椒也是，原因為何，可能來自於乾燥和疾病的壓力。

Hot chillies owe their mouth-watering bite to substances call capsaicinoids – a unique breed of chemical weapon wielded only by these plants. The weapon targets proteins that detect excessive heat, delivering an intense burning feeling without any actual burning. Birds, which pollinate chillies, don’t have these proteins and are immune to the fiery tastes. Mammals aren’t so fortunate; against them, capsaicinoids are an effective deterrent.
辣椒的武器源自於"capsaicinoids" 辣椒素，這是一種化學武器，這武器會攻擊蛋白質，提供一種灼熱感。鳥類授粉者可以躲過，因為它們沒有這類的蛋白質，不過哺乳動物可沒這麼幸運，辣椒素可是非常有效率的武器。

But pilfering mammals are not the biggest threats that wild chillies face. In 2008, Joshua Tewksbury at the University of Washington showed that their most important foe is a fungus called Fusarium semitectum, which rots the fruits and kills the seeds. Tewksbury showed that capsaicinoids kill the fungus, and chillies that lack their protection have half as many seeds in areas where Fusarium is around.
哺乳動物並不是辣椒最大的天敵，它們最主要的天敵來自一種菌類，它會造成果實的腐敗和種子的死亡，辣椒素可以殺死這些菌類，沒有他的保護，辣椒容易死亡。

Tewksbury studied wild chillies across 1,000 square miles of Bolivian rainforest. Those at the south-western corner are almost uniformly loaded with capsaicinoids, while most of those in the north-eastern corner aren’t hot at all. That seems puzzling: if being hot affords such valuable protection, why aren’t all chillies as pungent as possible?
研究指出，玻利維亞的雨林裡，西南區的辣椒充滿了辣椒素，但東北區的卻一點都不辣。如果辣椒素這麼有用，為何會有如此差異?

Back in 2008, Tewksbury suggested that the fungus was responsible – it’s more common in the south-western area. With less pressure to defend themselves, the north-eastern chillies could afford to be milder. But this explanation was never entirely convincing. Even in the north-east, the fungus was still a significant threat. Now, Tewksbury has a different idea. He thinks that being a red hot chilli pepper comes at a price: hot chillies suffer when it’s dry.
The chillies in Tewksbury’s patch of Bolivia experience very different levels of rainfall: the south-western corner is drenched in rain, and the north-eastern one is relatively dry. Tewksbury mimicked these conditions in a greenhouse.
研究人員早在2008就提出真菌的影響，但這無法解釋地區的差異，不過現在提出一個新看法，那就是乾旱。

When he gave the chillies all the water they wanted, all of them did equally well. When he deprived them of water, the ones that were fortified with capsaicinoids produced half as many seeds as their milder cousins. The hot plants have 40 percent more pores – stomata –on the undersides of their leaves, so they’re more likely to lose water when it’s dry. The milder plants, with their relatively sparser stomata, are better at retaining water.
研究人員將實驗分成二組，發現缺乏水份的那一組容易產生辣椒素，而較辣的那組有多出40%的氣孔，所以較容易排出水份

It might seem strange that hot flavours and drought tolerance could be so intimately connected. But Tewksbury thinks that the genetic changes which alter levels of capsaicinoids in the chillies’ fruits also affect the number of stomata in their leaves. He now wants to work out what these changes are.
辛辣度和乾旱如此相連，那它們是怎麼作用的呢?

On top of that, chillies produce capsaicinoids using the same sets of chemical reactions that produce lignin – the sturdy substance that coats their seeds. If they’re channelling their resources into defensive chemicals, they might not have enough to protect their seeds.
最重要的是，辣椒素的製造和木質素相同，一旦保護了個體，種子可就慘了，因為沒有足夠的外衣來保護種子

The fact that not all chillies are hot shows two important lessons about evolution. First, living things live in a world of varied restrictions, and something that’s adaptive in one place (like pungent chemicals) could be your downfall in another. Second, living things aren’t made from independent modules – it’s very difficult to tinker with one bit without affecting something else.
辛辣的演化告訴我們二件事，第一，生物在不同的環境有不一樣的反應，第二，生物產物並不一定獨立產生，有可能交叉交互影響。

For the chillies, the ideal situation would be to pack defensive chemicals while still resisting drought – that doesn’t seem possible. People often think that evolution is about progress and improvement; in reality, it’s more often about compromise and trade-offs.
對辣椒而言，最理想的是同時擁有辣椒素也能抗旱，但看來是不可能，人類常認為演化是改善且進步的，但現實看來常為妥協和權衡之計。