Cactus seedlings in the sun

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iann
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Cactus seedlings in the sun

Post by iann » Sun Jun 14, 2020 2:55 pm

Only early morning and evening when the sun sneaks under the staging, but it still colours up the seedlings.

Turbinicarpus laui
laui-0614.jpg
Turbinicarpus valdezianus
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Ariocarpus fissuratus
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Mammillaria grahamii
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Cheshire, UK
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ralphrmartin
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Re: Cactus seedlings in the sun

Post by ralphrmartin » Sun Jun 14, 2020 4:11 pm

Here's something I find intriguing. When cactus seedlings get too much sun, they go red. Yet plants on the forest floor often have red underleaves. In one case red seems like a reaction to excess light, and in the other case to a lack of light. Why red in each case?
Ralph Martin
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el48tel
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Re: Cactus seedlings in the sun

Post by el48tel » Sun Jun 14, 2020 4:53 pm

Not green means a lower level of chlorophyll in the plant in proportion to the other pigments which are red through yellow in colour.
Attempting to grow Aeoniums, Aylostera, Echinocereus, Echinopsis, Gymnocalycium, Lithops, Matucana, Rebutia, and Sulcorebutia.
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edds
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Re: Cactus seedlings in the sun

Post by edds » Sun Jun 14, 2020 5:01 pm

ralphrmartin wrote:
Sun Jun 14, 2020 4:11 pm
Here's something I find intriguing. When cactus seedlings get too much sun, they go red. Yet plants on the forest floor often have red underleaves. In one case red seems like a reaction to excess light, and in the other case to a lack of light. Why red in each case?
If I remember my plant physiology lectures correctly, some red pigments lie on top of green chlorophyll to act as sunscreen whereas some plants have different photosynthetic pathways using red pigments as the trees above have filtered out almost all of the green light so they photosynthesise using the red light.
Ed

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daydreamer
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Re: Cactus seedlings in the sun

Post by daydreamer » Sun Jun 14, 2020 6:41 pm

ralphrmartin wrote:
Sun Jun 14, 2020 4:11 pm
Here's something I find intriguing. When cactus seedlings get too much sun, they go red. Yet plants on the forest floor often have red underleaves. In one case red seems like a reaction to excess light, and in the other case to a lack of light. Why red in each case?
The reason advanced by David Attenborough for the red undersides is that it is a mechanism to reflect light that has passed through the leaf thickness and would otherwise be lost, so the plant gets a second bite at it. Presumably red colouration in seedlings is, as you say, protection against damage.
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Re: Cactus seedlings in the sun

Post by edds » Sun Jun 14, 2020 7:10 pm

edds wrote:
Sun Jun 14, 2020 5:01 pm
ralphrmartin wrote:
Sun Jun 14, 2020 4:11 pm
Here's something I find intriguing. When cactus seedlings get too much sun, they go red. Yet plants on the forest floor often have red underleaves. In one case red seems like a reaction to excess light, and in the other case to a lack of light. Why red in each case?
If I remember my plant physiology lectures correctly, some red pigments lie on top of green chlorophyll to act as sunscreen whereas some plants have different photosynthetic pathways using red pigments as the trees above have filtered out almost all of the green light so they photosynthesise using the red light.
I don't by the looks of a bit of research! The phytochrome detects the far red light and then encourages greater concentrations of chlorophyll b.
Ed

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Chris L
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Re: Cactus seedlings in the sun

Post by Chris L » Sun Jun 14, 2020 7:37 pm

ralphrmartin wrote:
Sun Jun 14, 2020 4:11 pm
Here's something I find intriguing. When cactus seedlings get too much sun, they go red. Yet plants on the forest floor often have red underleaves. In one case red seems like a reaction to excess light, and in the other case to a lack of light. Why red in each case?
Since many leaves are slightly transparent when held upto the light maybe the light has shone through the leaves and burnt the other side. :???: :???:
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Re: Cactus seedlings in the sun

Post by el48tel » Sun Jun 14, 2020 7:55 pm

edds wrote:
Sun Jun 14, 2020 5:01 pm
ralphrmartin wrote:
Sun Jun 14, 2020 4:11 pm
Here's something I find intriguing. When cactus seedlings get too much sun, they go red. Yet plants on the forest floor often have red underleaves. In one case red seems like a reaction to excess light, and in the other case to a lack of light. Why red in each case?
If I remember my plant physiology lectures correctly, some red pigments lie on top of green chlorophyll to act as sunscreen whereas some plants have different photosynthetic pathways using red pigments as the trees above have filtered out almost all of the green light so they photosynthesise using the red light.
Yes ... the structure of the plant has different pigments at different levels. Surprisingly, the infrared reflectance of cactus and succulents is very high compared to native UK plants.
Attempting to grow Aeoniums, Aylostera, Echinocereus, Echinopsis, Gymnocalycium, Lithops, Matucana, Rebutia, and Sulcorebutia.
Currently being wooed by Haworthia, and attempting hybridisation.
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Re: Cactus seedlings in the sun

Post by ralphrmartin » Sun Jun 14, 2020 8:09 pm

el48tel wrote:
Sun Jun 14, 2020 7:55 pm
Surprisingly, the infrared reflectance of cactus and succulents is very high compared to native UK plants.
Not sure what wavelengths you mean, but go far enough into infrared and you are talking of heat rays. I'm not surprised that cacti want to reflect heat rays, while British plants want to soak up the sun most of the year, if indeed those are the wavelengths you mean.
Ralph Martin
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Members visiting the Llyn Peninsula are welcome to visit my collection.

Swaps and sales at https://www.rrm.me.uk/Cacti/forsale.php

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Re: Cactus seedlings in the sun

Post by Licespray » Mon Jun 15, 2020 8:48 am

Interesting topic.

Ralph are those Ariocarpus out of humidity now?
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