Deciduous Trees with the sunlight coming through the leaves. The blue sky like a gem in the background, in this photo. by Farmer Jer.

Different Types Of Leaves And How Leaves Work

Different Types Of Leaves And How Leaves Work: This article will cover basic leaf anatomy and different types of leaves.  We’ll also take a look at how leaves work and that includes answering the question, how does photosynthesis work?  As we dive into the heart of the anatomy of leaves, it just wouldn’t be right if we didn’t talk about plant leaves that kill bugs and more.  So, join me on this wild journey down the rabbit hole (lined with leaves of course).

Different Types Of Leaves

There are many different leaf types.  There are nearly as many colors and shades of leaf type as there are leaf varieties.  The kinds of leaves you’ll find in different climate zones and conditions provide a glimpse into the brilliance of nature.  With so many varieties of leaves, it’s smart to get familiarized with the basic types and how each works.

According to Wikipedia, the types of leaves can be broken down into 6 basic leaf type categories1:

  1. Megaphylls (Fern Fronds)
  2. Conifer Leaves
  3. Angiosperm Leaves
  4. Microphyll Leaves
  5. Sheath Leaves
  6. Specialized Leaves

Fern Fronds – The Megaphylls

A fern is shown in this picture.
A Fern

Ferns are a unique group of plants that range from the arctic to the tropics.  They are unique in that they neither have seeds nor flowers. As well, adding to their uniqueness, ferns reproduce via spores, however, unlike mosses, ferns are vascular11.

Ok, so maybe we should get this translated into normal language, what do you say?  So, basically, ferns have a sort of vein or artery, much like many other plants. This ‘tube’ that is a part of the leaf anatomy (we’ll get to that) carries water and nutrients throughout the plant.  This vascular system extends throughout the fronds, or fern leaves if you’d like to call them that.

The fern leaves use photosynthesis to transform solar energy into chemical energy which they can use.  One of the neat tricks that ferns do is the way they release their new leaves by uncurling them. The tightly curled new leaves are called crozier, or more commonly, fiddleheads.  The latter is due to their resemblance to the tuning end of a fiddle.

A fern uncurling is shown in this picture.
A fern uncurls in this picture.

By Rror – Own work, CC BY-SA 3.0

Conifer Leaves

Conifer needles and baby cones are shown.
Conifer needles and baby cones are shown.

Around Southern Ontario, everyone knows about coniferous trees.  Although, we may not all know to call them coniferous. The trees are a famous part of our traditional Christmas.  Well, those Christmas trees we chop down every year to stuff presents under, has those pesky leaves. And those leaves come in the form of the infamous needles that make their way across the house when the tree starts to dry out.  

A northern landscape showing how the coniferous trees push right to the edge of the water, growing on what appears to be rock.
A northern landscape with the coniferous trees on the shoreline.

A little further north and… Ah, the great North.  Glorious, beautiful and pristine… Sorry, getting sidetracked (look at it, who wouldn’t?).  Back to the point (see what I did there?) The coniferous leaves, aka needles, have adapted to help the trees deal with the cold.  That’s why you’ll find them in boreal regions in the cooler climate areas of the world.  

These types of leaves are typically found on trees but not exclusively.  Their shape is thick, round tube-like structures, rather than their broadleaf cousins we all associate with the word leaf.

Angiosperm Leaves

A picture of a single leaf stuck in the sand on a beach is shown in this picture.  You can see the veins in the leaf due to the back lighting of sunlight on the leaf.
The most common leaves on earth – the Angiosperms.

The angiosperms are the most common plants found on land on Earth.  These are the flowering plants leaves. The ones which we all know to see.  This leaf variety is often wide, and thin. In these types of leaves, as you can clearly see in the picture above, the leaf has a distinct ‘vein’.  This main sort of channel travels from the base of the leaf and forms an almost tree-like pattern of a main stem and branches coming off of it. This is typical of an angiosperm leaf.

Many species of angiosperms lose their leaves in the fall.  This dramatic event is essentially known in the west to apply to the trees.  There are many other plants which lose their leaves though, not just trees. 

Microphyll Leaves

Microphyll leaves are shown in this picture.
Microphyll Single Vein Leaves

By Kirisame – Own work, CC BY-SA 3.0

In terms of vasculature, the microphyll is a single, unbranched vein leaf.  These plants have been found early on in the fossil record12.  They are only worth mentioning as they were likely the predecessor of today’s branched vascular system we see in leaves presently.  Well, I shouldn’t say they aren’t worth mentioning as there are more than 1250 species of Lycophyte and they are almost everywhere on Earth.

These very primitive forms of plants are the basic ancestor of todays more complex plant life, but as mentioned, they still exist as well in their ancient forms of having single veined leaves.  Imagine the leaf in the last picture with only the single vein, and no branching veins coming off of it. 

Sheath Leaves

The sheath leaf is the type you will find on many grasses.  They are typically straight and grow directly off a stalk, almost like an extension of the stalks out layer, peeling away from the stalk to bend and catch the sun.

Specialized Leaves

A specialized pitcher leaf is shown in this photo.
A pitcher leaf hangs ready to trap unsuspecting prey.

By -Jeremiah-The original uploader was JeremiahsCPs at English Wikipedia. – Transferred from en.wikipedia to Commons., Public Domain

A leaf is, according to Encyclopedia Britannica Online, is ‘any usually flattened green outgrowth’, protruding from the stem of a vascular plant2.  But, not all leaves were created equal.  There are some pretty specialized leaves out there in nature. 

Take the entrepreneurial plants like the pitcher plant, or the killer plants like the venus fly trap.  These plants have created singularly weird and strange new uses for leaves.  

The pitcher plant has grown to form its leaves into a water tight pitcher that traps rain water.  Not only does this help the plant in times of drought, but also allows the plant to do something else.  But wait! That’s not water inside that plant! It’s a digestive nectar!  

These sneaky plants attract bugs that go into the pitcher and get trapped by the slimy, slick walls and fluid.  And then the enzymes of the digestive fluid go to work on digesting the trapped bug. Kind of gross, kind of evil, these plants are predatory silent killers.

What Makes A Leaf – Leaf Anatomy 101

We all see them.  We all bask in the beauty of their change, come fall.  and most of us don’t have any idea about actual leaf anatomy.  The anatomy of leaves is a bit more complex than I used to think.  I thought the anatomy of a leaf was simple as they were just a part of a simple plant.  And plants aren’t exactly walking, thinking creatures (that we yet know of anyway).

Plant leaf anatomy is a complex collection of systems all slam packed into a highly efficient, often thin leaf.  However, not all leaves were created equal. There are a few different types of leaves and each of these has its own unique way of doing things.  Typically, the leaves are different based on their environment and climate. This can alter how the leaf anatomy makes the leaf work for the plants’ best interests in that particular climate.  Let’s take a look at the basic structure of a common leaf.

A diagram drawing of the cross section of a leaf.
By Zephyris – Own work, CC BY-SA 3.0

Annuals Vs Perennials

Interestingly, there are some distinct differences in the leaves of annuals versus those of perennial plants.  A study found that the leaves of the perennial plant were more dense than those of annuals. Also, the annuals were found to have a higher water content than those in the perennial group. Annuals also showed a greater amount of mesophyll cells within the leaves as compared to the perennials5.

How Leaves Work

I’ve often wondered how leaves work.  I mean, I know they are a major part of a plant.  An indispensable component, you might say. But, how do leaves work exactly?  How does a leaf work when it comes to changing sunlight into some form of usable energy?  And I’ve also wondered, in terms of gas exchange, how a leaf works.

Leaves don’t just add a vital part of energy and gas exchange for plants.  They also feed a huge portion of the food chain, despite not being as nutritious as other parts of a plant1.

Let’s take a look at the major functions of leaves, and how each works.

Leaves do a few major things:

  1. Photosynthesis
  2. Gas Exchange
  3. Look beautiful and inspire happiness in humans

How Photosynthesis Works And The Solar Connection

how photosynthesis works is a fairly complicated process involving some really cool organic chemistry.  Photosynthesis is the process of converting sunlight into energy. The process involves utilizing sunlight to produce glucose from carbon dioxide and water7.  Mankind has been trying to perfect a solar cell to attempt to recreate the wondrous process nature has created, but to nowhere near the ability which nature has shown us an example of.

But, how do plants get energy from the sun?  How these processes work is a matter of science.  And chemistry. And balance. It seems like an odd mix, chemistry, and balance, doesn’t it?  Let me explain.

The balance lies between animals and plants.  Plants take in energy from the sun via photosynthesis.  You’ve likely heard of chlorophyll. This is nature’s key to unlocking solar energy.  But it takes more than just chlorophyll to do the job.

Two Stage Process

How do plants absorb sunlight?  They use a two-stage process. The first stage really shows us how leaves take in the sun energy that bathes it during the day.  This stage involves light energy being trapped by chlorophyll to make ATP (photophosphorylation)8. During this time, water is separated as well.  It is split into oxygen, hydrogen and free electrons.

Here’s where the balance comes into play.  The oxygen is released for animals to breathe in and use.  And in turn, we generate and breathe out carbon dioxide. This CO2 is breathed in by the plants in order to add to the photosynthesis process.  It is vital for plants to make the sugars from the energy converted by the sunlight.

It’s this entire sun to sugar process that feeds the majority of life on Earth.  Those rays of life giving light are transformed by the wondrous leaf. The leaf does the most efficient job on Earth of converting energy.  None of our technology has been able to even come close to the efficiency that life has already created. At least, not at the time of writing this article anyway.

Killer Plants Which Have Plant Leaves That Kill

There are, believe it or not, plant leaves that kill.  These killer plants have honed their skills over millions of years to capture their prey.  Deadly plants, plants that kill bugs with zero remorse grow and exist right now, right here on Earth.

But have no fear, these plants aren’t out to get you.  Just some bugs who foolishly wander into the traps that these plants have made out of leaves.  Wait, what? Out of leaves? Like, plant leaves that kill bugs or something? Yeah, that’s right.

There are three more predominantly common forms of killer plants.  There are the fastest plants in the west, the Venus Flytrap. I’m sure you’ve heard of that one.  Its leaves have eyelash like parts that protrude off the edge of the leaves. They also have smaller hairs that sense movement.  This special leaf-type springs to action when a fly triggers the tiny sensor hairs9.

A video short of a moving venus flytrap.
Venus Flytrap

By Mnolf – Own work, CC BY-SA 3.0

The specialized leaves of the Venus Flytrap use enzymes, just like a pitcher plant does, which digest the bugs that get trapped by these carnivorous leaves10.  These plants have inspired crazy fantastical beasts such as the plant found in the Little Shop Of Horrors movie.  I wouldn’t want to be a little fly and wander into one of these. What a gruesome way to go.

Speaking Of Leaves

What about bagging leaves that cover the lawn in fall from the trees.  Well, fallen leaves of deciduous trees typically contain about 0.5 percent nitrogen, 0.1 percent phosphorus, and 0.5 percent potassium.  They also contain many other nutrients which the tree has pulled from the soil around.  

Bagging leaves in the fall is basically the process of removing a bunch of nutrients from the soil in that area and shipping the nutrients away in bags.  Now here’s the catch, if you leave the leaves covering your lawn, they’ll kill the grass. That’s because they will shield the grass from sunlight and the grass with its sheath leaves needs that sun to survive.  

So, the question is, how do we use those leaves to fertilize the soil, without having to leave them all over the lawn to kill the grass?  

A Leafy Solution

The solution that I use is a mulching compost system.  I have a big wooden compost bin at the back of my property.  Before I put grass trimmings from the lawnmower, or leaves that I have raked up, I shred them.  All the leaves must be obliterated and shredded. That way, you speed the time it takes to compost.  I mix about 50/50 dirt to compost with the bin mid spring every year and use the mix to fertilize my lawn and gardens.

To fertilize the lawn with this shredded leaf and dirt mix, I just sprinkle a little around the lawn before a rain or before I’m about to water the grass.  That way the water washes the dirt/compost mix down into the soil and provides the lawn with nutrients.  

To add to my gardens where I grow veggies, I use the mix in the early spring before planting, and bury a bunch of the mix in rows under where I’m going to plant my vegetables.  I’ve had a lot of success with both of these methods, both for my lawn and also for my garden. Waste not.

Do you have any good tips for leaves?  Leave a comment below and let everyone know your secret for leaves.

Bibliography

  1. https://en.wikipedia.org/wiki/Leaf#Basic_leaf_types
  2. https://www.britannica.com/science/leaf-plant-anatomy
  3. https://journals.abcjournal.aosis.co.za/index.php/abc/article/view/1382/1341
  4. https://www.journals.uchicago.edu/doi/abs/10.1086/335974
  5. https://nph.onlinelibrary.wiley.com/doi/abs/10.1111/j.1469-8137.1994.tb04036.x
  6. http://www.plantphysiol.org/content/63/4/700.short
  7. https://www.rsc.org/Education/Teachers/Resources/cfb/Photosynthesis.htm
  8. https://www.pbs.org/wgbh/nova/nature/photosynthesis.html
  9. https://en.wikipedia.org/wiki/Venus_flytrap
  10. https://www.britannica.com/plant/carnivorous-plant
  11. https://en.wikipedia.org/wiki/Fern#Distribution_and_habitat
  12. https://en.wikipedia.org/wiki/Microphylls_and_megaphylls
  13. https://en.wikipedia.org/wiki/Lycophyte

Join Farmer Jer on his Gardening Adventure

Subscribe to the Farmer Jer newsletter.