Penyerapan Hara Oleh Akar Tumbuhan
Transcript of 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