TRANSPIRASI

1. TRANSPIRASI Hery Purnobasuki 2008

2. 1 2 3 4 Through stomata, leaves take in CO2 and expel O2. The CO2 provides carbon for photosynthesis. Some O2produced by photosynthesis is used in cellular respiration. Sugars are produced by photosynthesis in the leaves. Transpiration, the loss of water from leaves (mostly through stomata), creates a force within leaves that pulls xylem sap upward. 6 5 7 Water and minerals are transported upward from roots to shoots as xylem sap. Roots absorb water and dissolved minerals from the soil. Roots exchange gases with the air spaces of soil, taking in O2 and discharging CO2. In cellular respiration, O2 supports the breakdown of sugars. • A variety of physical processes of transportation in plant • Are involved in the different types of transport CO2 O2 Light H2O Sugar Sugars are transported as phloem sap to roots and other parts of the plant. O2 H2O CO2 Minerals

6. Casparian strip Endodermal cell Pathway along apoplast 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 Plasma membrane 1 Minerals and water that cross the plasma membranes of root hairs enter the symplast. Apoplastic route 2 Vessels (xylem) 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. Root hair Symplastic route Epidermis Endodermis Vascular cylinder Cortex 5 4 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. 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. Figure 36.9 Lateral transport of minerals and water in roots

7. Key Symplast Apoplast Transmembrane route Apoplast The symplast is the continuum of cytosol connected by plasmodesmata. The apoplast is the continuum of cell walls and extracellular spaces. Symplast Symplastic route Apoplastic route Transport routes between cells. At the tissue level, there are three passages: the transmembrane, symplastic, and apoplastic routes. Substances may transfer from one route to another. (b) Figure 36.8b • 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 • Along the apoplast

8. Teori tentang transport air dalam tanaman 1. Teori vital 2. Tekanan akar 3. Hukum kapilaritas 4. Teori kohesi 5. Transpirasi

10. 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 theair surrounding the plant • Most transpiration occurs via the leaves • Most of this transpiration is via the stomata. Ψtanah > Ψakar > Ψbatang > Ψdaun > Ψudara

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

12. Pengukuran transpirasi menurut Salisbury & Ross (1991) Lysimeter / Gravimetric Method - Pengukuran langsung Gas exchange / Cuvette Method - Pengukuran uap air Stem-Flow Methods

13. How Transpiration is Measured 1’’’’’’’’2’’’’’’’’3’’’’’’’’4’’’’’’’’5’’’’’’’’6’’’’’’’’7’’’’’’’’8’’’’’’’’9’’’’’’’’10’’’’’’’’11’’’’’’’’12’’’’’’’’13’’’’ Water evaporates from the plant A Simple Potometer Leafy shoot cut under water Air tight seals Capillary tube Plastic tubing Movement of meniscus is measured over time Graduated scale

14. The rate of water loss from the shoot can be measured under different environmental conditions Water is pulled up through the plant volume of water taken up in given time Limitations • measures water uptake 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

15. Tipe transpirasi: • Transpirasi kutikula • - 10% atau kurang dari jumlah air yang hilang 2. Transpirasi stomata 3. Transpirasi lentisel

17. 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.

18. The guard cells control the opening and closing of the stomata Guard cells flaccid Guard cells turgid Thin outer wall Thick inner wall Stoma open Stoma closed

19. Regulating Stomatal Opening:-the potassium ion pump hypothesis Guard cells flaccid 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 K+ K+ K+ K+ Stoma closed

20. H2O H2O H2O H2O H2O Regulating Stomatal Opening:-the potassium ion pump hypothesis Increased concentration of K+ in guard cells K+ K+ Lowers the  in the guard cells K+ K+ K+ K+ K+ K+ K+ Water moves in by osmosis, down  gradient K+ K+ K+

21. Guard cells turgid Increased concentration of K+ in guard cells H2O H2O K+ K+ Lowers the  in the guard cells K+ H2O H2O K+ K+ K+ K+ K+ K+ H2O H2O K+ Water moves in by osmosis, down  gradient K+ K+ Stoma open

22. 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 CO2 cause guard cells to become flacid • Leaves lost when water is scarce

23. 6 Environmental Factors Affecting Transpiration • 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 • 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. • 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

24. 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.

25. Intrinsic Factors Affecting the Rate of Transpiration. • Leaf surface area • Thickness of epidermis and cuticle • Stomatal frequency • Stomatal size • Stomatal position

27. 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)

28. 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)

29. 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

31. Peranan Transpirasi Merupakan proses pendinginan (daun) Pemindahan panas Mempengaruhi keadaan sekitar Bagian dari siklus air

32. 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 30oC (> suhu udara) Transpirasi tak bermanfaat Catatan: rumus-rumus keseimbangan panas pada daun dapat dibaca di Salisbury & Ross (1991), Plant Physiology.

33. Jenis air dalam tanah: 1. Air kimia 2. Air higroskopik / hidrasi 3. Air gravitasi 4. Air kapiler

34. 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

37. Aktifitas pengukuran laju transpirasi pada tanaman

38. 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?