Photosynthesis question?

[nao57]

So, I've been wondering about this for awhile. You have 2 sides of a leaf. For tree leaves especially like apple tree leaves the top side will be darker and have sort of a darker color. The underside will be ... it looks less developed. As if the underside doesn't do as much as the top.

This makes me wonder if in general this is true for most plants? What do you think about this? Specifically, is photosynthesis only going on on the top side of the leaves? I'd kind of like to especially get input on this for fruit and nut trees and vegetable plants (basically food production plants).

Here's some specific leaves I noticed some things;

Certain types of evergreens like arbor vita (Christmas trees) look very flat on the branches. Those leaves are somewhat flat also but look similar on both sides.

Apple tree leaves look like the top is more developed.

Peach tree leaves its sort of close but it looks like the leaf top is slightly more developed but more equal comparing bottom and tops. Plum tree leaves look less developed on bottom also.

Aspen tree leaves you can't really tell which side is the top and bottom because they are built to move in the wind.

Evergreen trees in general it doesn't look like the top and bottom are different.

Garden vines such as pumpkins, squash, and others the bottom of the leaves look very different than the tops, and look a bit underdeveloped suggesting there'd be less chemical activity going on if any also.

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But here's an example why this could be used;

Part of why I was asking about this is because there's this tomato leaf illness they call 'leaf curl disease'. And specifically someone treating it might could try splinting some of those leaves to save it. Similarly other very dehydrated plants someone could try to split the backs with something temporarily also. But to do that you'd have to know if the tops and bottoms of various plants get photosynthesis from both sides or only the top?

There were a few times this year where I wanted to save a plant that was very dehydrated and leaves were curling. In the early part someone could probably reverse the leaf curling if it hasn't taken off too much. Probably they could do that with bits of cardboard and attach them to the backs of leaves. And some cardboard is very light.

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PS; as a bonus, I'm throwing in something delicious to try today as a simple recipe. We tried this today from garden produce. You take the juiciest tomatos possible. Then thin slice them using a serrated knife. Then do light bit of salt on the slices. You also while doing this have a good quality type of hot dogs or beef franks frying in a pan nearby. When the hot dogs are ready you wrap the tomato slices around them. Because they are already juicy and the hot dogs are juicy too, this feels like the thing i'd like something for a person's bucket list to try.

 

[Meadowlark]

Specifically, is photosynthesis only going on on the top side of the leaves?

I've been doing some research on your question. The short answer is "no" both sides are critical and photosynthesize... the top more so than the underside. Both sides have kind of different roles to play which is very interesting to me.

Top side (adaxial surface) is far more efficient because it contains the palisade mesophyll — the layer with the highest density of chloroplasts and thus highest level of photosynthesis.

Underside (abaxial surface) contains the spongy mesophyll, which has fewer chloroplasts and more air spaces. It houses most of the stomata, which let CO₂ in and O₂ out — essential for photosynthesis. I thought this was especially interesting about the underside... less photosynthesis yes, but a critical gas exchange function.

 

[nao57]

I've been doing some research on your question. The short answer is "no" both sides are critical and photosynthesize... the top more so than the underside. Both sides have kind of different roles to play which is very interesting to me.

Top side (adaxial surface) is far more efficient because it contains the palisade mesophyll — the layer with the highest density of chloroplasts and thus highest level of photosynthesis.

Underside (abaxial surface) contains the spongy mesophyll, which has fewer chloroplasts and more air spaces. It houses most of the stomata, which let CO₂ in and O₂ out — essential for photosynthesis. I thought this was especially interesting about the underside... less photosynthesis yes, but a critical gas exchange function.

Wow. That's amazing! thank you for the chance to speak with you. You have some great information and I learn something when talking to you.

 

[Meadowlark]

Well, it is mutual @nao57 .

Bread experiment coming because of your thoughtful posts. Thanks.

 

[Martin Mikulcik]

Leaves aren't opaque either so the light can hit the chloroplasts to some degree even through the wrong side, and conifers are as you suggest mostly the same which way you look at it

A pine needle

 

[DirtMechanic]

I've been doing some research on your question. The short answer is "no" both sides are critical and photosynthesize... the top more so than the underside. Both sides have kind of different roles to play which is very interesting to me.

Top side (adaxial surface) is far more efficient because it contains the palisade mesophyll — the layer with the highest density of chloroplasts and thus highest level of photosynthesis.

Underside (abaxial surface) contains the spongy mesophyll, which has fewer chloroplasts and more air spaces. It houses most of the stomata, which let CO₂ in and O₂ out — essential for photosynthesis. I thought this was especially interesting about the underside... less photosynthesis yes, but a critical gas exchange function.

So basically plant leaves fart out Oxygen through thousands of buttholes.

FIFY

PS. Don't forget the top side impact of colors as they relate to radiant heat. Infrared in particular. Blue and Yellow and Red light. Let's see, blue and yellow make green, it is reflected so we see it and blue is phasing down from Ultraviolet which is high energy and also a ionizing radiation, Yellow is the central band more or less of the visible band which is half the energy, and Red Light is progressively hotter and hotter yet when it stretches out to become invisible infrared so seeing red leaves when the chlorophyll goes away is part of the cooling system. Probably makes it a darker green, where darker colors may absorb more heat but they also release it faster, a property called emission. Leaves are cool by color design but farting air through a thousand buttholes is hard to beat for the coolest feature.

 

[Esther Knapicius]

I read somewhere years ago that a plant that has variegated leaves, White and Green, that the White part does not have the same sun absorption properties as the green part. Therefore it's position needs more sun than the same type plant with all green leaves. Example I have a variegated hydrangea, also have other hydrangeas with solid green leaves. So I placed my variegated one on the out skirts area where it gets more sun during the day, but also less shade as the sun moves across that area. Others get less direct sun and more shade.

I also have a hydrangea that the top part of its leaves are a dark green, and the belly part pure white. it seems to do well in a medium sun/shade situation for the last 20 years. Flowers nicely every year.

Now you got me thinking, with hosta's they always seem to recommend that the Yellow type should be placed in deeper shade so the yellow pops color for the garden view, and my Yellows do well in that position.

So, its not the depth of green color that marks its ability to absorb sun???

 

[DirtMechanic]

I read somewhere years ago that a plant that has variegated leaves, White and Green, that the White part does not have the same sun absorption properties as the green part. Therefore it's position needs more sun than the same type plant with all green leaves. Example I have a variegated hydrangea, also have other hydrangeas with solid green leaves. So I placed my variegated one on the out skirts area where it gets more sun during the day, but also less shade as the sun moves across that area. Others get less direct sun and more shade.

I also have a hydrangea that the top part of its leaves are a dark green, and the belly part pure white. it seems to do well in a medium sun/shade situation for the last 20 years. Flowers nicely every year.

Now you got me thinking, with hosta's they always seem to recommend that the Yellow type should be placed in deeper shade so the yellow pops color for the garden view, and my Yellows do well in that position.

So, its not the depth of green color that marks its ability to absorb sun???

The word may be "reflect" rather than "absorb". The heaviness and density of a leaf can help describe how much heat may be held in leaves as each molecule can hold an X amount of energy. The color is a reflection and this frequency is not absorbed. Also shine helps reflection, as well as other protections. Here at my location the difference in june temps between a dense material white and dense material black can be 50f or 10c. I surmise that outside of specifically bred hybridized foliage the natural plants may well have developed leaves according to their initial development environmental needs. Tomato a highly emissive matte and a my big magnolia from a completely different world a dark but reflective leaf. Where white is the reflection of all color (even silver maple type colors) the black is the absorbing of that energy. All that energy sloughs off through emission or the result is disintegration of the molecule, like scalding or collapsed spinach in my pot. The defense of that cooking effect is the density of the leave where a less dense leaf can get the heat to the bottom side and out through the stomata. Plants know water carries a superheat and punches above its weight in terms of cooling. Nuclear power and other energy producers use this same property in what is called the Carnot Cycle. Plants just knew it first. I often wonder if leaves that are dense and heavy like my magnolia are strong enough to trap pressure like steam makes before it's released with a slightly higher heat content through the evaporation process. A stomata and a giant power plant cooling tower have a lot in common.

Here finding really cool ir pictures of tree leaves reflecting infrared light, and the bark absorbing it. As you know hot liquids rise, like the hot water in your water tank so plants also knew this first. These nice photos are phase shifted for your eyes to see it as white.

Exploring The Wood Effect in Infrared Photography | JoeFarace.com

joefarace.com

And meanwhile, somewhere in China...

Scientists built a sunflower-inspired cooling system that delivered 135% more cooling power at solar noon than a fixed horizontal surface - The Times of India

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