Penyerapan Hara Oleh Akar Tumbuhan

8/10/2019 Penyerapan Hara Oleh Akar Tumbuhan

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PM PSLP PPSUB MALANG 2011

PENYERAPAN

UNSUR HARA

OLEH

AKAR TUMBUHAN

Penyunting:Soemarno


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PENYERAPAN UNSUR HARA

OLEH

AKAR TUMBUHAN

Cetakan : IMalangProgram Pascasarjana, Universitas Brawijaya, Malang

Viii : 60 hlm : 20 cm x 25 cm

Penyunting: Soemarno

Tata Letak :

Grafis & Desain Sampul : Soemarno

Hak Cipta pada penulis.

Cetakan Pertama Agustus 2011

Penerbit : PPSUB

Jl. Mayjen MT. Haryono 165, Malang

Tel. 0341-571260


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KATA PENGANTAR

Dengan memanjatkan puji syukur kehadirat Allah swt, atas segala

karunia-Nya, penyusunan buku Bahan Kajian mengenai PENYERAPAN

UNSUR HARA OLEH AKAR TUMBUHAN ini dapat diselesaikan.

Buku memori ini menyajikan data, informasi dan konsep-konsep

tentang Pengelolaan Hara Tanaman yang relevan dengan filosofi

Sustainable Crop Management.

Data dan infromasi yang disajikan dalam tulisan ini dihimpun dari

beragam pengalaman dan dari berbagai sumber yang dianggap valid,

termasuk hasil-hasil pengkajian yang tersebar di berbagai referensi .

Dengan telah selesainya Buku ini, perkenankanlah kami mengucapkan

terima kasih yang sebesar-besarnya kepada semua pihak yang telah

membantu, terutama kepada rekan-rekan sejawat yang telah secara

tulus ikhlas memberikan informasi yang ada kaitannya dengan

penyusunan buku ini.

Semoga informasi yang terkandung dalam buku ini dapat dimanfaatkansebagaimana mestinya bagi pengembangan pembelajaran pada program

pascasarjana di Universitas Brawijaya.

Malang, Agustus 2011

Penyunting

Soemarno


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DAFTAR ISI

Pendahuluan .. 1

Unsur Hara Tanaman .. 2

Sistem Perakaran Tanaman .. 7

Penyerapan air dari tanah .. 10Penyerapan Hara Tanaman .. 19

Mekanisme Penyediaan Unsur Hara .. 22

Mekanisme Penyerapan Hara .. 29

Mikorizha .. 34Serapan Hara Tanaman (Nutrient Uptake) 41

Hubungan Kandungan N dengan Hasil .. 47

Efisiensi Pupuk N pada Padi .. 48


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KETERSEDIAAN

UNSUR HARA


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ZONE UJUNG AKAR

Plants absorb water through the entire surface - roots, stems and

leaves. However, mainly the water is absorbed by roots. The area

of young roots where most absorption takes place is the root hairzone. The root hairs are delicate structures which get continuously

replaced by new ones at an average rate of 100 millions per day.

The root hairs lack cuticle and provide a large surface area. They

are extensions of the epidermal cells. They have sticky walls by

which they adhere tightly to soil particles. As the root hairs are

extremely thin and large in number, they provide enormous

surface area for absorption. They take in water from theintervening spaces mainly by osmosis.


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PERTUKARAN ION

Ion exchange theory

Both cations and anions have a tendency to getadsorbed on the surfaces of the cell walls, and

exchange with ions present in the soil solution. This

process of exchange between the adsorbed ions andions in solution is known as ion exchange.


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SIKLUS UNSUR HARA

Biogeochemical cycle of mineral nutrients in

agricultural ecosystems


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Types of roots:

Seminal root - from a seed

Adventitious root - from a

stemFirst order lateral root - from

a seminal or adventitious

root

Second order laterals, etc. -

from first order laterals,

which in turn produce third

order laterals, and so on . . .Feeder roots - fine, relatively

short-lived roots that

acquire nutrients and water

in the topsoil

Primary roots - from primary

growth by the apical

meristem

Secondary roots - mature,

thicker "woody" roots with

bark and additional vascular

tissue

Coarse roots - may live for along time and have roles in

transport and mechanical

support


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KETERSEDIAAN

UNSUR HARA

Iron Uptake and TranslocationIron is primarily taken up by plants as the ferrous (Fe2+) iron.

However, because most agricultural soils contain iron in the

ferric (Fe3+) form, plant must somehow first solubilise the Fe3+

and then reduce it to Fe2+so that it can pass through the root

hair plasma membrane (plasmalemma).

In dicotyledoneous species (ie most crops), iron uptake is an

active, energy, requiring process.


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THE UPTAKE OF WATER FROM THE SOIL TO THE

LEAVES

The cytoplasm of root hair cells is usually hypertonic to thesurrounding soil water. Hence, water enters the root hair cells by

osmosis. The root hair cells are now hypotonic to the adjacent root

cortex cells. Water then diffuses into these cells until it reaches the

cortex region. Water flows through the parenchyma cells (cortex)

until it reaches the endodermis through either the apoplastic pathway

or the symplastic pathway . The Casparian strips (impermeable to

water) prevent water from moving through the cell wall of theendodermal cells. The water concentration gradient which exists

across the cortex creates a transpiration pull to direct water into the

xylem vessels. Water finally reaches the mesophyll cells in theleaves where it will be lost through the stomata into the surroundings


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Ion homeostasis: plants feel better

with proper controlThe model plant species, thale cress (Arabidopsis thaliana,

right) and rice (Oryza sativa, left), are displayed as a

chimera. (A) OsHKT2;1 functions as a transporter for Na+uptake. (B) QSO2, a flavoprotein quiescin sulphydryl

oxidase, is a new component in ion homeostasis at the root

symplastxylem interface. (C) Downregulation of

OST2/AHA1 H+-ATPase activity is a prerequisite for ABA-

induced stomatal closure. ABA, abscisic acid; OST2/AHA,

OPEN STOMATA 2.

http://www.nature.com/embo

r/journal/v8/n8/fig_tab/7401040_F1.html

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Penyerapan Hara Oleh Akar Tumbuhan