PM-PSLP PPSUB MALANG-2011

PENYERAPAN UNSUR HARA

OLEH AKAR TUMBUHAN

Penyunting: Soemarno

PENYERAPAN UNSUR HARA OLEH

AKAR TUMBUHAN

Cetakan : I – MalangProgram Pascasarjana, Universitas Brawijaya, MalangViii : 60 hlm : 20 cm x 25 cm

Penyunting: Soemarno

Tata Letak :Grafis & Desain Sampul : Soemarno

Hak Cipta pada penulis.Cetakan Pertama Agustus 2011Penerbit : PPSUB

Jl. Mayjen MT. Haryono 165, Malang Tel. 0341-571260

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 dimanfaatkan sebagaimana mestinya bagi pengembangan pembelajaran pada

program pascasarjana di Universitas Brawijaya.

Malang, Agustus 2011

Penyunting

Soemarno

DAFTAR ISI

Pendahuluan …….. 1

Unsur Hara Tanaman …….. 2

Sistem Perakaran Tanaman ….. 7

Penyerapan air dari tanah ….. 10

Penyerapan Hara Tanaman ….. 19

Mekanisme Penyediaan Unsur Hara ….. 22

Mekanisme Penyerapan Hara ….. 29

Mikorizha ………………….. 34

Serapan Hara Tanaman (Nutrient Uptake) ……… 41

Hubungan Kandungan N dengan Hasil …….. 47

Efisiensi Pupuk N pada Padi …….. 48

KETERSEDIAAN UNSUR HARA

ZONE UJUNG AKARPlants 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 hair

zone. 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 the

intervening spaces mainly by osmosis.

PERTUKARAN ION

Ion exchange theoryBoth cations and anions have a tendency to get adsorbed on the surfaces of the cell walls, and

exchange with ions present in the soil solution. This process of exchange between the adsorbed ions and

ions in solution is known as ion exchange.

SIKLUS UNSUR HARABiogeochemical cycle of mineral nutrients in

agricultural ecosystems

Types of roots:

Seminal root - from a seedAdventitious 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 a long time and have roles in transport and mechanical

support

.

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.

THE UPTAKE OF WATER FROM THE SOIL TO THE LEAVES

The cytoplasm of root hair cells is usually hypertonic to the surrounding 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 the endodermal 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 the

leaves where it will be lost through the stomata into the surroundings

Ion homeostasis: plants feel better with proper control

The 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 symplast–xylem 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/embor/journal/v8/n8/

fig_tab/7401040_F1.html