Hery Purnobasuki



2008

• A variety of physical processes of transportation in plant – Are involved in the different types of transport

4

Through stomata, leaves take in CO 2 The CO 2 and expel O 2 . provides carbon for photosynthesis. Some O 2 produced by photosynthesis is used in cellular respiration.

3

Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward.

H 2 O

2

Water and minerals are transported upward from roots to shoots as xylem sap.

CO 2

1

Roots absorb water and dissolved minerals from the soil.

H 2 O Minerals O 2 Sugar

5

Sugars are produced by photosynthesis in the leaves.

Light O 2 CO 2

6

Sugars are transported as phloem sap to roots and other parts of the plant.

7

Roots exchange gases with the air spaces of soil, taking in O 2 and discharging CO 2 . In cellular respiration, O 2 supports the breakdown of sugars.

Lateral transport of minerals and water in roots

Pathway along apoplast Casparian strip Endodermal cell Pathway through symplast

1

Uptake of soil solution by the hydrophilic walls of root hairs provides access to the apoplast. Water and minerals can then soak into the cortex along this matrix of walls.

Casparian strip

2

Minerals and water that cross the plasma membranes of root hairs enter the symplast.

1

Plasma membrane Apoplastic route

2 3

As soil solution moves along the apoplast, some water and minerals are transported into the protoplasts of cells of the epidermis and cortex and then move inward via the symplast.

Symplastic route

Figure 36.9

4

Within the transverse and radial walls of each endodermal cell is the Casparian strip, a belt of waxy material (purple band) that blocks the passage of water and dissolved minerals. Only minerals already in the symplast or entering that pathway by crossing the plasma membrane of an endodermal cell can detour around the Casparian strip and pass into the vascular cylinder.

Root hair Vessels (xylem) Epidermis Cortex Endodermis Vascular cylinder

5

Endodermal cells and also parenchyma cells within the vascular cylinder discharge water and minerals into their walls (apoplast). The xylem vessels transport the water and minerals upward into the shoot system.

• Water and minerals can travel through a plant by one of three routes

– Out of one cell, across a cell wall, and into another cell – Via the symplast

Key

– Along the apoplast Symplast Apoplast Transmembrane route Apoplast The symplast is the continuum of cytosol connected by plasmodesmata.

Symplast The apoplast is the continuum of cell walls and extracellular spaces.

Symplastic route Apoplastic route

Transport routes between cells.

At the tissue level, there are three

(b)

passages: the transmembrane, symplastic, and apoplastic routes. Substances may transfer from one route to another.

Figure 36.8b

Teori tentang transport air dalam tanaman

1. Teori vital 2. Tekanan akar 3. Hukum kapilaritas 4. Teori kohesi 5. Transpirasi

Transpiration

• Transpiration is the loss of water from a plant by

evaporation

• Water can only evaporate from the plant if the

water potential

is

lower

in the

air

surrounding the plant • Most transpiration occurs via the leaves •

Most

of this transpiration is

via the stomata

.

Ψtanah > Ψakar > Ψbatang > Ψdaun > Ψudara

PENGUKURAN TRANSPIRASI

1. Kertas Cobalt Chlorida 2. Fotometer 3. Pengumpulan uap air 4. Penimbangan Langsung

Pengukuran transpirasi menurut Salisbury & Ross (1991)

Lysimeter / Gravimetric Method - Pengukuran langsung Gas exchange / Cuvette Method - Pengukuran uap air Stem-Flow Methods

How Transpiration is Measured A Simple Potometer Leafy shoot cut under water Air tight seals Plastic tubing Water evaporates from the plant Capillary tube

1’’’’’’’’2’’’’’’’’3’’’’’’’’4’’’’’’’’5’’’’’’’’6’’’’’’’’7’’’’’’’’8’’’’’’’’9’’’’’’’’10’’’’’’’’11’’’’’’’’12’’’’’’’’13’’’’

Graduated scale Movement of meniscus is measured over time

The rate of water loss from the shoot can be measured under different environmental conditions Water is pulled up through the plant Limitations

•measures water uptake

volume of water taken up in given time

1’’’’’’’’2’’’’’’’’3’’’’’’’’4’’’’’’’’5’’’’’’’’6’’’’’’’’7’’’’’’’’8’’’’’’’’9’’’’’’’’10’’’’’’’’11’’’’’’’’12’’’’’’’’13’’’’ •cutting plant shoot may damage plant •plant has no roots so no resistance to water being pulled up

Tipe transpirasi:

1. Transpirasi kutikula

10% atau kurang dari jumlah air yang hilang

2. Transpirasi stomata 3. Transpirasi lentisel

Water and Mineral Movement

• Regulation of transpiration – Stomata open and close due to changes in turgor pressure of guard cells.

• Turgor results from active uptake of potassium (K + ) ions.

– Increase in K + concentration creates a water potential that causes water to enter osmotically, guard cells to become turgid, and stomata to open.

The guard cells control the opening and closing of the stomata

Guard cells flaccid Thin outer wall Guard cells turgid Stoma closed Thick inner wall Stoma open

K +

Regulating Stomatal Opening:-the potassium ion pump hypothesis

Guard cells flaccid

K + K + K + K +

K + ions have the same concentration in guard cells and epidermal cells

K + K + K + K + K + K + K +

Light activates K + pumps which actively transport K + from the epidermal cells into the guard cells Stoma closed

Regulating Stomatal Opening:-the potassium ion pump hypothesis

H 2 O H 2 O H 2 O Increased concentration of K + in guard cells K + H 2 O K + K + K + K + K + K + K + K + K + K + K + H 2 O Lowers the



guard cells in the Water moves in by osmosis, down



gradient

Guard cells turgid

K + H 2 O K + K + H 2 O K + H 2 O K + K + H 2 O + K + H 2 + O K + H 2 O K + K +

Stoma open

Increased concentration of K + in guard cells Lowers the



cells in the guard Water moves in by osmosis, down



gradient

Some other facts about the stomata

• • • • •

Open in the day and closed at night - need carbon dioxide in the daylight for photosynthesis When water is scarce, plant wilts and guard cells become flacid Abscisic acid - plant hormone that causes K + to pass out of cells and guard cells become flacid High levels of CO 2 flacid cause guard cells to become Leaves lost when water is scarce

6 Environmental Factors Affecting Transpiration 1. Relative humidity

:- air inside leaf is saturated (RH=100%). The lower the relative humidity outside the leaf the faster the rate of transpiration as the  gradient is steeper

2. Air Movement

:- increase air movement increases the rate of transpiration as it moves the saturated air from around the leaf so the  gradient is steeper.

3. Temperature

:- increase in temperature increases the rate of transpiration as higher temperature – Provides the latent heat of vaporisation – Increases the kinetic energy so faster diffusion – Warms the air so lowers the  of the air, so  gradient is steeper

4.

Atmospheric pressure

:- decrease in atmospheric pressure increases the rate of transpiration.

5.

Water supply

:- transpiration rate is lower if there is little water available as transpiration depends on the mesophyll cell walls being wet (dry cell walls have a lower  ). When cells are flaccid the stomata close.

6.

Light intensity

:- greater light intensity increases the rate of transpiration because it causes the stomata to open, so increasing evaporation through the stomata.

Intrinsic Factors Affecting the Rate of Transpiration.

1. Leaf surface area 2. Thickness of epidermis and cuticle 3. Stomatal frequency 4. Stomatal size 5. Stomatal position

Nama Tanaman

Polypodium nidus

(Paku Pandan)

Gnetum gnemon Rhoeo discolor Gloriosa superba Zephyranthes rosea Typha domingensis Areca catecha Imperata cylindrical Alpenia galangal (Lengkuas) Phalaenopsis amabilis Ficus elastica Helianthus annuus Lycopersicum esculentum Zea mays Solanum tuberosum Begonia coccinea Coleus blumei Pelargonium domesticum

Banyaknya stoma per mm 2 pada permukaan atas

0 0 0 0-1 70 350 0 320 0-2 10 0 210 130 68 161 40 141 59

bawah

85 335 30 120 50 560 250 340 200 30 200 250 2 E 52 E 51 M 0 E 0 E 19 E

Jenis tanaman berdasarkan kondisi air di habitatnya: 1. Tanaman air (hidrofit) 2. Tanaman daerah basah (higrofit) 3. Tanaman daerah sedang (mesofit) 4. Tanaman daerah tropis (tropofit) 5. Tanaman daerah kering (xerofit)

Jenis tanaman pada tanah yang kurang air

1. Efemera

Tumbuh sebentar, di gurun-gurun

2. Sukulenta

Berdaun tebal, berlapis lilin, sedikit stoma, stoma tersembunyi, banyak akar

Cactaceae, Euphorbiaceae, Liliaceae, Amaryllidaceae, Crassulaceae dan Aizoaceae

3. Xerofit

Tahan kekeringn dan akar panjang (+30 m)

Adaptations to reduce transpiration loss in plants growing in dry conditions (xerophytes)

Thick cuticles - prevent water loss from epidermal cells Succulent (thick) leaves - store water Loss of leaves/reduction of leaves to form spines - light is not limiting, so photosynthesis can be carried out by the shoot. What type of plant am I describing? White leaves/spines - light colors reflect light and heat, thereby cooling the plant Trichomes (hairs) - create a more humid microenvironment to reduce evaporative water loss Sunken stomates - like trichomes, a more humid microenvironment is created CAM photosynthesis - stomates open during the night (when it is cooler) and fix CO2 into four-carbon acids The light reaction occurs during the day, generating NADPH and ATP Rolled leaves : this reduces the area exposed to the air and keeps the stomata on the inside so increasing the water vapour inside the roll

Peranan Transpirasi

Merupakan proses pendinginan (daun) Pemindahan panas Mempengaruhi keadaan sekitar Bagian dari siklus air

Contoh perubahan energi dalam ekosistem: Padang Pasir

Suhu  , radiasi  , kelembaban  , air  Mengatur kelembaban dan menjaga suhu rendah daun Daun kecil, lapisan pembatas sel tipis, transfer panas efektif

Alpine Tundra

Dingin, cukup lembab, radiasi  , air cukup Rata-rata suhu daun 30 o C (> suhu udara) Transpirasi tak bermanfaat Catatan: rumus-rumus keseimbangan panas pada daun dapat dibaca di Salisbury & Ross (1991), Plant Physiology.

Jenis air dalam tanah:

1. Air kimia 2. Air higroskopik / hidrasi 3. Air gravitasi 4. Air kapiler

GUTASI

Penetesan /pengeluaran air melalui lubang-lubang di tepi daun Berlangsung pada malam hari Lubang-lubang tersebut  hidatoda ( emisaria ) dimana terdapat jaringan epitema di dalamnya Terjadi karena adanya tekanan akar dan faktor lainnya

Aktifitas pengukuran laju transpirasi pada tanaman

SOAL

1. Apakah pengaruh transpirasi pada peresapan air oleh akar?

2. Bagaimana cara kita membuktikan bahwa lalu lintas dalam pembuluh kayu (xilem) itu tidak satu jurusan saja?

3. Bagaimana teori kohesi mendukung transport air dalam tanaman? Dan bagaimana hubungannya dengan transpirasi? 4. Mengapa transpirasi melalui kutikula lebih sedikit dibandingkan dengan stomata? Bagaimana cara membuktikannya?

5. Jelaskan faktor-faktor yang dapat mempengaruhi proses transpirasi?

6. Jelaskan faktor-faktor yang dapat mempengaruhi proses gutasi? Dan apakah perbedaan gutasi dan transpirasi?