"Radix alias Akar"

Alhamdulillah saya diberi kesempatan untuk dapat menambah isi dari blog ini, pembahasan kali ini adalah materi pertama dalam Sistem dan Perkembangan Tumbuhan, yaitu struktur luar organ vegetatif, pada tumbuhan Spermatophyta.

Yang harus kita ketahui terlebih dahulu, apa sih akar itu? mari kita mulai pembahasannya.

Jelas disini apa yang dimaksud dengan akar, sebuah organ utama pada tumbuhan yang berfungsi sebagai penyerap unsur hara dan juga air dari tanah, menegakkan tumbuhan itu sendiri, dan juga bermetamorfosis menjadi sebuah alat ayng memiliki beraneka-ragam fungsi, contohnya sebagai alat penempel ataupun alat respirasi.
Perkembangan akar pada tumbuhan berbiji dimulai dari lembaga, pada radicula, membentuk radix primarius (akar primer).

Ada dua macam sistem perakaran pada tanaman Spermatophyta, yakni sistem akar serabut dan sistem akar tunggang.

Anatomi akar dapat dijelaskan dengan gambar berikut:



Dapat kita lihat, gambar di atas adalah contoh akar tunggang. Mulai dari atas terdapat leher akar, batas antara akar utama dengan batang. Kemudian terlihat jelas akar utama. Yang membentuk percabangan ke samping, disebut cabang akar atau radix lateralis. Dari cabang akar membentuk percabangan bertingkat, disebut serabut akar atau Fibrilla radicalis. Di seluruh bagian akar terdapat bulu akar atau pilus radicalis. dan di setiap ujung akar terdapat caliptra yang berfungsi untuk memudahkan akar dalam menembus tanah.

Terdapat tiga macam jenis akar tunggang:
1) Akar tombak (fusiform) >> besar di pangkal, runcing di ujung
2) Akar gasing (napiform) >> akar utama pangkal membulat
3) Akar benang (filiform) >> akar utama kecil panjang

Sedangkan pada sistem akar serabut, akar utama / akar primer tereduksi sehingga akar tumbuh pada buku-buku batang. Terdapat tiga macam juga:
1) Akar serabut kecil >> Oryza sativa
2) Akar serabut sedang >> Cocos nucifera
3) Akar serabut besar >> Pandanus tectorius



Selain sistem perakaran, hal penting lain dari akar adalah bahwa akar mengalami metamorfosis, sehingga berpengaruh pada fungsi akar tersebut yang otomatis berubah, dan hal ini disebabkan karena adaptasi spesies tertentu terhadap lingkungannya.

1) Akar papan (butreess)
>> Beralih fungsi untuk menegakkan berdirinya tajuk tumbuhan. Umumnya terdapat pada tumbuhan hujan tropis. Contohnya Canarium comunne.

(http://www.dkimages.com/discover/previews/818/40010434.JPG)


2) Akar tunjang (stilt)
>> Hidup pada daerah berlumpur, membantu menegakkan tumbuhan itu sendiri. Contohnya Pandanus tectorius.

(http://www.5thworld.net/nov99/Img/OtherStuff/Plants/WarmPonds/Hala.jpg)


3) Akar pelekat (radic adligans)
>> Digunakan tumbuhan untuk merambat. Contohnya Piper betle (sirih).

(http://batakone.files.wordpress.com/2009/09/sirih-piper-betle1.jpg)


4) Akar udara (radix aureus)
>> Umumnya pada tumbuhan epifit, digunakan untuk bernafas dan menyimpan air. Contohnya pada kelas anggrek (Orchidaceae) dan pada Ficus benjamina (Beringin).

(http://2.bp.blogspot.com/_ERrg6joD1So/SXvu8ba_y_I/AAAAAAAAAFM/Bea5bXfndC0/S730/dsc00421.jpg)


5) Akar Pengisap (haustoria)
>> Pada tumbuhan parasit, digunakan untuk menempel dan menghisap unsur-unsur penting dari tumbuhan yang ditempelinya itu. Contohnya Dendrophthoe pentandra, atau yang lebih kita kenal dengan benalu.

(http://www.parasiticplants.siu.edu/Loranthaceae/images/DendrophthoePent.jpg)


6) Akar Nafas (pneumatophora)
>> Dimiliki oleh tumbuhan pada habitat lumpur, membantu pernafasan. Contohya pada tumbuhan bakau. Saya ambil contoh Sonneratia alba.

(http://www.hawaii.edu/cpis/MI/gallery/images/bulabol%20-%20Sonneratia%20alba.jpg)


7) Akar lutut (knee)
>> Mirip dengan akar nafas, ditemukan pada tumbuhan dengan habitat lumpur. Contohnya Bruguiera gymnorhiza (Pohon tancang).

(http://oceangrow.septentriones.com/data/upimages/mangroves_2y_1_640v480.jpg)


8) Akar Pembelit (cirrhus radicalis)
>> Dimiliki oleh tumbuhan untuk memanjat. Contohnya Vanilla planifolia.

(http://aerialphotolab.com/DOinc/2004-05-14_Vanilla_planifolia_fruit.jpg)


9) Umbi akar (Tuber rhizogenum )
>> Digunakan tumbuhan tersebut sebagai tempat penyimpan makanan. Contohnya Manihot utilisima. Ini kita kenal dengan ubi kayu, dan merupakan salah satu bahan dasar yang dibawa saat ospek kemarin, haha.

(http://warintek.bantulkab.go.id/basisdata/Budidaya_Pertanian/images/singkong.jpg)


10) Duri akar (spina rhizogenum)
>> Contohnya Dioscorea aculeata. Masih belum tahu fungsinya.

(http://users.telenet.be/sf16063/pauwels/DiosBulb.jpg)


Demikian tadi sekilas tentang jenis akar, metamorfosis akar, beserta contoh-contohnya. Saya ucapkan terima kasih kepada seluruh pemilik alamat gambar yang saya sertakan dibawah masing-masing gambar diatas. Semoga informasi ini dapat bermanfaat dalam pembelajaran.

Sumber : Struktur dan Perkembangan Tumbuhan, karangan Dr. L. Hartanto Nugroho, M. Agr. dkk.

Fakultas Biologi, Universtas Gadjah Mada

35 comments:

ifa said...

Makach bget yup artkel amu ne,,bantu q bgt.. dlm ngrj'n tgas antum q..

bonas said...

koq blom di post in akar banir nya kak ......

Knowledge Blog said...

itu paling atas gambar akar tunggang kan kk....
ada gambar akar serabutnya gak?

umie widya said...

sebelumnya syukron bwat anda, karna artikel anda sangat membantu tgas + presentasi ana....

Inckz Weithzon Putra said...

Kang, ada makalah yg membahasa tentang akar ga??????????

aku butuh nich gan....

send me dunkz via this email

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via said...

ttddkk aadd,mank na untk ap yha.....




inckz weithzon putra said...

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Situ Morrow said...

wah, pas masuk blog ini, kaget gue.....ada yang suit-suitin gue segala.

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