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Main content
Current time:0:00Total duration:6:54
AP.BIO:
ENE‑3 (EU)
,
ENE‑3.D (LO)
,
ENE‑3.D.1 (EK)

Video transcript

phototropism implants as a response in which a plant shoot grows toward a light source the results of five different experimental treatments from classic investigations of phototropism are shown above Part A gives support for the claim that the cells located in the tip of the plant shoot give support for the claim that the cells located in the tip of the plant shoot detect the light by comparing the results from treatment Group one with the results from treatment group two and treatment group three so we want to compare these first first three treatment groups and you see when you have an all unaltered tip that the whole plant is going to bend in the direction of the light when you remove the tip it no longer bends in the detent the in the direction of the light or if you were to cover the tip with some type of an opaque cap so the light can't go through it it's still not going to Bend so this is pretty good evidence that there's some there's something about the tip of the plant that allows the phototropism to occur it allows the plant to know which direction the light is and then makes and then somehow causes it to bend in that direction so I'll just write that down give support for the claim so we can say that phototropism phototropism phototropism only occurred only occurred when there is a an unaltered tip unaltered tip that has access to the light that has access to light no bending occurred no bending occurred occurred when either the tip was removed the tip was removed that was that was treatment - so treatment treatment - or the tip was tip had an opaque cover the tip had an opaque cover that was treatment treatment treatment 3 so that's all there is to it it only occurred when there was an alt altered tip so that was treatment one that has access to light no bending occurred when either the tip was removed when this one in treatment - or treatment 3 so it's a pretty good indication you need that tip and it needs to have access to the light something about the tip let's the plant know what direction to start bending in alright let's do Part B now Part B in treatment groups 4 and 5 so that's these two treatment groups right over here the tips of the plants are removed and placed back onto the chute on either a permeable or impermeable barrier using the results from treatment groups 4 & 5 describe two additional characteristics of the phototropism response well when the tip was placed on top of a permit permeability ilysm still happens the plant still bends so even though the the tip is disconnected because this barrier is permeable the tip must be able to sense the light and release some type of substance or hormone or chemical or something that's able to go through this per meal permeable barrier some type of substance that goes through this permeable barrier and somehow signals to the rest of the plant to bend in the right direction because when you put an impermeable barrier right over here the the tip might be trying to release those same substances but they can't get through and so the rest of the plant doesn't know to bend or in what direction to bend so we could say we could say tip tip must release some type of hormone hormone I say chemical chemical that signals to rest of plant to bend to bend and in which direction which direction we know this we know this because only the or only XA treatment for only treatment for treatment for permeable barrier and I'll say where the where the barrier is permeable to that substance where the barrier is permeable permeable to that substance that substance we know this because only treatment for where the barriers permit of the substance shows shows phototropism phototropism not treatment treatment 5 we know this we could say because of the 2 of 4 and 5 only treatment for where the barrier is permeable to that substance shows tropism phototropism that's the only explanation here that it's not doing it through somehow doing through radio waves or releasing substances that somehow float in the air to the rest of the plant that somehow some subtype of substance is going through through directly from the the tip to the rest of the plant and when block it is not able to send those chemical signals that's that's the best that's the best explanation that I can think of for this behavior that we see between treatments four and five
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