f4 bio

首先你要明白, 書上而所寫的close, 其實都是relatively講
如果有足夠的光線而進行photosythesis, stomata打開了一個小口, 相對在, 沒有足夠光線的時候, stomata的小開口較細, 甚至乎小小得好像close了一樣, 但不代表gas不能進出那小小得像close了的入口 (氣體份子很很很小哦)

為什麼stomata會打開. 其實最重要是個photosythetic rate影響
在al的課程之中, 會詳細地教
不過你應該知道, 水是photosythesis的原料 ()
當有光的時候, chlorophyll已經開始photosythesis
最初個rate較慢的時候, 會先用掉從自己plant cell中respration得來的co2去做photosythesis (個時stomata 都未開)
個rate慢慢快, 所要的水也更多, 水就自然地更多地enter cell by osmosis
gard cell的結構上也很特別, 一邊的cell wall厚一點點, 另一邊又薄一點點
所以當水enter, 令guard cell trugid, 佢就會因為兩邊cell wall的不同厚度而有不同的expansion, 形成了一個新月形, 兩個guard cell就變成了stomata中的那個開口了

rate越快, 自己產生出的co2已經唔夠用, 所以要從外面取,
stomata的open就幫助引入更多co2

到了晚上, photosythetic rate係零, 但repiration rate仍是跟日間一樣, 相對地須要的水就不是那麼多, cell 就會比較flaccid, stomata就會變細甚至乎close了

晚上的repiration放出的期中一少部份co2 (dissolved form as acid)的確會對cell 的turgity有影響, 不過最重要還是photosythetic rate

還有, 日間做photosythesis時出的o2大部份都會排出植物外, 晚上時只剩下一點點, 其餘的就只是靠intercellura space的o2, 及從stomata進入的那一點點空氣中的o2 維生

再打多個比喻
你關了(close)門, 是不是就得於沒有任何氣體可以進入房間內??
可進入的氣體少了, 但不是沒有嘛, 氣體從什麼地方進入房間, 你都應該知道吧

我都已經很多年沒有用bio d字, 可能會串錯, 請見諒

可以看一下
http://www.estrellamountain.edu/faculty/farabee/biobk/BioBookPS.html

First, Why the stomata close in the dark?
According to my book,
more than 90% of the water transpired by the plant is lost through the stomata. So closing of the stomata prevent loss of water.

What is the mechanism of closing the stomata?
To make it simple: at night,in most species, the stomata may respond to changes in carbon dioxide and an increase in carbon dioxide concentration causes the stomata to close. (Light is also another factor to trigger the closing of the stomata.)
But closing of stomata also prevent entry of carbon dioxide into the leaf.

To sum up, I think respiration at night will use the oxygen produced by photosynthesis in the daytime and the carbon dioxide will accumulate in the plant cells at night.
As the concentration of carbon dioxide in the cells is low in the daytime (due to photosynthesis), the concentration increases at night. So the stomata respond the the increase in concentration and close.

我覺得會~
stomata allow the gas diffuse in and out
oxgen release and carbon dioxide is absorded by respiration
所以應該會ga.
除非果棵植物係1cell thick and no cuticle
咁gas就可以diffuse directly.