The Truth About Shade Leaves
Everyday here at RIU some one ask should I trim the leaves? here lately it seems more and more members are getting it and telling the new growers NO, which is a good thing!
What would you say if I said that those shaded leaves are actually more productive for the plant?
Before I explain, let me say that we tend to call the leaves of our beloved MJ plant FAN leaves cause they are shaped like a fan. But in reality there are two types of leaves SUN leaves (the ones in the light) and SHADE leaves (the ones in the shade). Also please understand that it is the leaves that make the bud, the buds do not use light the same way that the leaves do and a plant without it's leaves will not yield big buds, period!
Getting back to my statement about leaf production, here is a quote from a texas aggie site,,,,,,,
Research done in Florida in the late 1970's revealed an interesting phenomenon. Tropical plants grown in full sun have leaves (so called sun leaves) which are structurally different from the leaves of plants grown in shade (shade leaves). Sun leaves have fewer chloroplasts and thus less chlorophyll. Their chloroplasts are located deep inside the leaves and the leaves are thick, small and large in number. Shade leaves have greater numbers of chloroplasts and thus more chlorophyll, are thin, large and few in number. When plants are grown in strong light they develop sun leaves which are photosynthetically very inefficient. If these same plants are placed in low light, they must either remake existing sun leaves or drop their sun leaves and grow a new set of shade leaves which are photosynthetically more efficient.
Now armed with these two terms we can do a simple google for the term sun leaves versus shade leaves and get a whole bunch of great info
this quote is about trees but carries very important info with regard to how the different types of leaves help the plant,,,,,
Trees need tremendous amounts of water on a daily basis. Even though it may not rain every day, a trees' roots spread through the ground absorbing water. A mature oak tree needs 40-60 gallons of water every day. Trees have ways of conserving water, because water is very precious to a tree. One way in which a tree helps to conserve water is to develop two kinds of leaves. There are sun leaves and shade leaves. Sun leaves are small, with less surface area, which reduces the amount of exposure to the sun and wind. A shade leaf is large, with greater surface area, which increases the amount of area exposed to the sun. Remember, it is important for a tree to have its leaves exposed to the sun so that photosynthesis (food making) can take place, but not so much that it loses too much water.
And from the same site a bit of explanation,,,,,,,,
Every tree or plant has a daily need for water. The cell, as the basic unit of life, is 75% water. Therefore, if a tree is to live, its cells must have enough water. A tree loses water by a process known as evapo-transpiration. Evaporation of water is increased by heat and wind. Transpiration is the movement of water from the roots through the stem to the leaves where evaporational losses can be high. The leaves must have a continuous supply of water to avoid dehydration and to carry out photosynthesis.
The effect of heat and wind on leaf water loss is greatest at the top of the tree. A tree, or any other plant, has several strategies to reduce the inevitable loss of water. There is a waxy covering (cuticle) on the leaf to reduce desiccation. Stomata (leaf openings which are necessary for gaseous exchange, but do enhance evaporation) are concentrated on the underside of the leaf so as not to be directly exposed to the sun. Stomata guard cells close when evaporation conditions are most intense.
Shade leaves and sun leaves are different. Surface area is a key consideration in reducing water loss. The less surface area that is in contact with wind or heat, the less water is lost. In other words, small is good when in direct contact with the sun. When considering the entire set of leaves on the tree, one notices that some of the leaves receive direct exposure to the sun, and other leaves receive indirect sun because of shading by other leaves. Sun leaves are found on the top part of the crown. Shade leaves are found on the bottom part of the crown especially on the north side, and have a larger surface area. Determining a ratio between shade leaves and sun leaves on a tree helps a forester or arboriculturist determine its tolerance or intolerance to shade. A tree that has a high ratio of shade leaves to sun leaves indicates it is tolerant to shade. In other words, the tree does not mind growing in the shade and is a species that is able to grow as a sapling under a dense forest canopy.
There will be a few folks that will hollor that this info is not about MJ but it relates to all plants and is based in simle botany that applies to all plants
which leads us to my favorite quote,,,,,,,,,
Abstract.Light gradients were measured and correlated with chlorophyll concentration and anatomy of leaves in spinach (Spinacia oleracea L.). Light gradients were measured at 450, 550 and 680 nm within thin (455 μm) and thick (630 μm) leaves of spinach grown under sun and shade conditions. The light gradients were relatively steep in both types of leaves and 90% of the light at 450 and 680 nm was absorbed by the initial 140 μm of the palisade. In general, blue light was depleted faster than red light which, in turn was depleted faster than green light. Light penetrated further into the thicker palisade of sun leaves in comparison to the shade leaves. The distance that blue light at 450 nm travelled before it became 90% depleted was 120 μm in sun leaves versus 76 μm in shade leaves. Red light at 680 nm and green light at 550 nm travelled further but the trends were similar to that measured at 450nm. The steeper light gradients within the palisade-of shade leaves were caused by increased scattering of light within the intercellular air spaces and/or cells which were less compact than those in sun leaves. The decline in the amount of light within the leaf appeared to be balanced by a gradient in chlorophyll concentration measured in paradermal sections. Progressing from the adaxial epidermis, chlorophyll content increased through the palisade and then declined through the spongy mesophyll. Chlorophyll content was similar in the palisade of both sun and shade leaves. Chloroplast distribution within both sun and shade leaves was relatively uniform so that the chlorophyll gradient appeared to be caused by greater amounts of chlorophyll within chloroplasts located deeper within the leaf. These results indicate that the anatomy of the palisade may be of special importance for controlling the penetration of photo-synthetically active radiation into the leaf. Changing the structural characteristics of individual palisade cells or their arrangement may be an adaptation that maximizes the absorption of light in leaves with varying mesophyll thickness due to different ambient light regimes.
Seems like every day I tell some one that plants do not see/react to light the same way we do, I hope that I have better explained for everyone now. Why it is so important to give your plants the proper spectrum of light as opposed to tons of lumens
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