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Seed germination
Light is a major environmental factor that influences seedling development. During seed germination, light controls whether seedlings develop normally (de-etiolation) or abnormally in the dark (etiolation). In the dark, seedlings undergo etiolation with limited organ development and no chlorophyll production. When exposed to light, seedlings undergo de-etiolation where they develop properly with chlorophyll synthesis and organ development. This process of de-etiolation from the etiolated state to normal growth is triggered by light and involves photoreceptors such as phytochromes that detect light and induce changes in seedling development.
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Seed germination
- 1. 1 Light control ofplant development : Seed germination and de- etiolation
- 2. 2 Light in plant’slife Light – major environmental factor influencing the course of seedling development
- 3. Iriawati, SITH -ITB 3
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- 5. 5 Seed germination • vulnerable/ susceptible life stage in plant development • sensor & mechanism respond to environmental condition (ex. light, water condition, gravity etc) • transition between embryonic and postembryonic development • Post embryonic shoot development Activation of SAM first true leaf
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- 7. Iriawati, SITH -ITB 7 Storage Protein Amino Acids Barley Seed Germination Fruit+Seed Coat Endosperm Aleurone Layer hydrolysis translation transcription hydrolysis sugar α-amylase RNA DNA GA imbibition water radicle apex shoot apex growthcotyledon monocot maltose Embryo exocytosis starch Amino Acids Storage Protein
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- 15. Iriawati, SITH -ITB 15 Etiolation
- 16. Iriawati, SITH -ITB 16 Seedling development • In the dark : etiolation - skotomorphogenesis – No chlorophyll production – Limited and/or abnormal organ (root, stem, leaf) development • When exposed to light : de- etiolation - photomorphogenesis – Chlorophyll synthesis – Proper development begins • Why the difference? – Limited seed reserves – Efficient use of resources until capable of Ps (i.e., chorophyll production).
- 17. De-etiolasi • Transformasi darikondisi etiolasi ke kondisi dengan pertumbuhan normal (green state) • Bisa terjadi beberapa saat setelah kecambah yang mengalami etiolasi terpapar oleh cahaya. • Cahaya akan menginduksi pengurangan kecepatan elongasi sel batang, pelurusan apical hook, inisiasi pembentukan atau perkembangan pigmen fotosintetik , energi bagi proses fotosintesis • Sehingga fotosintesis bukanlah yang menginduksi de-etiolasi karena klorofil tidak terbentuk, akan tetapi cahaya 17
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- 19. Iriawati, SITH -ITB 19 De-etiolasi
- 20. 20 Photomorphogenesis • Sejumlah perubahanyang terjadi saat de- etiolasi terjadi karena tanaman melakukan respon terhadap cahaya • Photomorphogenesis ‘light form begins’ • Pertumbuhan tanaman merupakan respon terhadap cahaya yaitu terhadap perubahan jumlah, tipe, durasi dan arah datangnya cahaya. • Membutuhkan Photoreceptors, yang membuat tanaman dapat mengintepretasikan cahaya • Photoreceptor : phytochrome menyerap cahaya merah dan merah jauh (far red), serta reseptor cahaya biru
- 21. 21 Phytochrome • Pigments that absorbred (665 nm) and far-red (730 nm) light. • Ubiquitous in plants, role in most all plant development. • Phytochrome can interconvert between Pr and Pfr
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- 23. Iriawati, SITH -ITB 23 Lettuce Seed Germination 660 nm 730 nm dark Seed Coat translation transcription hydrolysis starch sugar α-amylase RNA DNA imbibition water radicle apex shoot apex growthdicot photoreversibility Pfr Prphotoactivation Embryo phytochrome red and white light stimulate germination cotyledons
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