Respons tunas: pertumbuhan tidak merata menyebabkan kelengkungan
Diperkenalkan| English | Makna |
|---|---|
| phototropism/ˌfəʊtəʊˈtrəʊpɪzəm/ | fototropisme |
| auxin/ˈɔːksɪn/ | auksin |
What would explain this observation?
- A seedling bending towards light has not simply moved its whole stem sideways. Different growth on its two sides changes its direction.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Plants produce hormones coordinating growth and responses to light and gravity. Phototropism 向光性 is a growth response to light; gravitropism is a growth response to gravity. Unequal auxin 生长素 distribution causes unequal growth in roots and shoots. In the usual shoot model, more auxin on the shaded side increases elongation there, bending the shoot towards light.
- phototropism: A directional growth response to light; auxin: A plant hormone involved in coordinating growth responses.
Mengapakah anak pokok yang dinyatakan membengkok ke arah cahaya?
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Auksin terkonsentrasi di sisi teduh tunas dan mempromosikan lebih banyak elongasi di sana, sehingga sisi teduh tumbuh lebih panjang dan tunas melengkung menuju cahaya. Pertumbuhan terus berlanjut di kedua sisi—tidak setara—yang membuat tunas bengkok.
Pasangkan setiap istilah teknis dengan maknanya yang tepat.
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Gunakan definisi untuk membedakan besaran dan proses yang terkait.
Choose evidence that can test it
- Roots and shoots respond differently. In a horizontal root, more auxin on the lower side inhibits elongation relative to the upper side, so the root bends downwards. In a shoot, greater lower-side elongation bends it upwards. Explain the growth difference rather than claim that gravity pulls all the cells into a new shape.
- For RP8 use teacher-approved newly germinated seedlings. Compare a planned light direction or orientation with a suitable control, keeping species, initial age, water, temperature and observation time comparable. Record lengths and careful labelled drawings showing direction. Do not test hormone effects on people; avoid touching growing tips or changing light and gravity conditions simultaneously.
Dua kebiasaan manakah yang membuat penyelidikan atau model dalam kasus ini lebih dapat dipertanggungjawabkan?
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Menyatakan kondisi dan asumsi memungkinkan orang lain mengulangi pekerjaan persis seperti itu, dan mencatat bukti pendukung memungkinkan mereka memeriksa kesimpulan. Menyembunyikan hasil yang bertentangan menghilangkan bukti yang dapat menentang kesimpulan yang salah, dan satu pengukuran tidak pernah dapat menetapkan klaim yang lebih luas.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: a fictional shoot model grows 6 mm on its shaded side and 4 mm on the illuminated side during one interval. Growth difference = 2 mm. The longer side helps explain bending towards light, but this difference alone does not calculate the bend angle without geometry and tissue information.
A supplied shoot model has growth of 9 mm and 5 mm on opposite sides. Calculate the difference. Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
Model tunas yang disediakan menunjukkan pertumbuhan 9 mm dan 5 mm pada sisi yang berlawanan. Hitung perbedaannya.
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Hasilnya adalah 4 mm. Diketahui: pertumbuhan 9 mm di satu sisi dan 5 mm di sisi lain. Perbedaan = 9 - 5 = 4 mm. Sisi yang lebih panjang mendorong kelengkungan; perbedaan saja tidak memberikan sudut lentur tanpa geometri.
Check the conclusion and its limits
- A tropism is growth in relation to a directional stimulus, not every plant movement. Auxin does not have the same elongation effect in every root and shoot situation. Gibberellin and ethene roles are Higher Tier and are taught separately.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Auxin always has an identical elongation effect in roots and shoots. This claim is false: Auxin's effect depends on the tissue and concentration: shoots elongate more at concentrations that can inhibit root elongation, so roots and shoots do not respond identically.
Seedling responses: unequal growth makes a bend: Roots and shoots respond differently. In a horizontal root, more auxin on the lower side inhibits elongation relative to the upper side, so the root bends downwards. In a shoot, greater lower-side elongation bends it upwards. Explain the growth difference rather than claim that gravity pulls all the cells into a new shape.
Auksin sentiasa mempunyai kesan pemanjangan yang sama pada akar dan anak pokok.
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Efek auksin bergantung pada jaringan dan konsentrasi: tunas mengalami elongasi lebih besar pada konsentrasi yang dapat menghambat elongasi akar, sehingga akar dan tunas tidak merespons secara identik.
Tindak balas pertumbuhan berarah terhadap cahaya: tulis istilah teknikal.
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fototropisme bermaksud Tindak balas pertumbuhan berarah terhadap cahaya.