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神秘的植物冷知識~~~泌水孔
2024/05/19 05:47
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泌水孔是一種位於分泌組織,通常在被子植物被發現,由孔洞表皮或葉邊緣分泌水分,經常位於齒狀或鋸齒狀邊緣的尖端。泌水孔出現在沉水性水生植物(如:Ranunculus fluitans[1])與在乾旱棲地的草本植物(如:圓葉風鈴草[2])。他們以維管束鞘與植物維管束系統連結,泌水孔通常在大薸、鳳眼藍、玫瑰、膠冷杉中被觀察到。

泌水孔由一群具有充滿水的大型胞外空間的活細胞組成,但沒有或只有少量葉綠體,代表特化鞘體末端。這些細胞(稱為披覆組織細胞)[3]向外開口進入一個或多個表皮下腔室。他們輪流透過開水氣孔(open water stoma)與開孔(open pore)與外界溝通。水氣孔在結構上與正常氣孔相似,但通常較大且失去運動的能力。

泌水孔與泌液作用的過程有關,在此正的木質部壓力(由於根壓)使液體由這些孔洞向外滲出[4]。一些鹽土植物擁有腺狀毛狀體有效地分泌鹽分因而降低在細胞質中的細胞毒性無機離子的濃度;這造成了在葉表面的白色粉狀物質的形成。

泌水孔有兩種:

  • 被動泌水孔(passive hydathode):再披覆組織內的葉脈末端形成。
  • 主動泌水孔(active hydathode):在表皮細胞主動失去水分時形成。

我的高中同學說:
這是小葉欖仁樹,靱性超强,其水份供輸只靠形成層兩側,竟也能撐得住,爬山常見這種幹朽到空薄,只剩皮層的達摩形松柏,那時的心得是,木質部的水份供給應該是貯存功能大矜輸送,意即木質部主要功能是支撐,次為膨漲壓的維持兼作水份貯存,輸送水份應該是被動功能,意即水份是因為葉芽表面蒸散後因調控膨脹壓穩定,而順便擔任虹吸管。
在美國時,因為天氣熱,水壓因此增加,為了調整回來,就常看到許多大樹頂端,自然產生泌溢噴水汽的現象。
Simon & Garfunkel - The Sound of Silence - Madison Square Garden, NYC - 2009/10/29&30
Hello darkness, my old friend
Ive come to talk with you again

Because a vision softly creeping
Left its seeds while I was sleeping
And the vision that was planted in my brain
Still remains
Within the sound of silence
In restless dreams I walked alone
Narrow streets of cobblestone
Neath the halo of a street lamp
I turned my collar to the cold and damp
When my eyes were stabbed by the flash of a neon light
That split the night
And touched the sound of silence
And in the naked light I saw
Ten thousand people, maybe more
People talking without speaking
People hearing without listening
People writing songs that voices never share
No one dared
Disturb the sound of silence
"Fools" said I, "You do not know
Silence like a cancer grows
Hear my words that I might teach you
Take my arms that I might reach you"
But my words like silent raindrops fell
And echoed in the wells of silence
And the people bowed and prayed
To the neon god they made
And the sign flashed out its warning
In the words that it was forming
And the sign said, "The words of the prophets
Are written on the subway walls
And tenement halls
And whispered in the sounds of silence"

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