Gerak pada Tumbuhan


 Jika pada hewan rangsang disalurkan melalui saraf, maka pada tumbuhan rangsang disalurkan melalui benang plasma (PLASMODESMA) yang masuk ke dalam sel melalui dinding yang disebut NOKTAH.
Gerak pada tumbuhan dibagi 3 golongan, yaitu :

1.
Gerak HIGROSKOPIS

yaitu gerak yang ditimbulkan oleh pengaruh perubahan kadar air.

Misalnya:
- gerak membukanya kotak spora.
- pecahnya buah tanaman polong.
2.
Gerak ESIONOM

yaitu gerak yang dipengaruhi rangsang dari luar.

a.
TROPI (TROPISME) yaitu gerak bagian tumbuhan yang dipengaruhi oleh arah rangsang. Tropisme positif jika mendekati rangsang dan tropisme negatif jika menjauhi.
Bentuk tropisme antara lain
- fototropisme atau heliotropisme
- geotropi
- tigmotropi atau haptotropi Þ rangsang berupa sentuhan
- hidrotropi
b.
TAKSIS yaitu gerak berpindah seluruh tubuh tumbuhan yang dipengaruhi oleh rangsang. Seperti bentuk tropisme, terdapat taksis positif dan negatif.
Beberapa bentuk taksis :
- fototaksis
- kemotaksis
c.
NASTI yaitu gerak bagian tumbuhan yang tidak dipengaruhi arah rangsang. Gerak ini disebabkan terjadinya perubahan tekanan turgor akibat pemberian rangsang.
Beberapa bentuk nasti :
- Niktinasti Þ rangsang berupa gelap
- Seismonasti Þ rangsang sentuhan atau mekanik
- nasti kompleks Þ rangsang tidak hanya satu
Contoh : gerak membuka dan menutupnya sel-sel penutup stomata Þ rangsang berupa cahaya, suhu, air, dan zat kimia

3.
Gerak ENDONOM

yaitu gerak yang belum/tidak diketahui sebabnya. Karena belum diketahui sebabnya ada yang menduga tumbuhan itu sendiri yang
menggerakkannya Þ gerak OTONOM, misalnya aliran plasma sel.

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