It's All About Leaves

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Posted by @wildflowers on
Leaves so often take a back seat to the more showy and colorful flowering blooms and fruits. While we wait for spring to arrive, let's take a look at leaves as the star attraction.

 

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As spring draws nearer, many of us anticipate the return of leaves on trees and shrubs after what seemed like a long, barren and cold winter.  It's always exciting seeing shades of green unfold, sleepy trees wake up and new sprouts emerge from bare ground, all right before our eyes. The hickory is among the last of the trees to bud; around here it's the last to show signs of life.  That's a sure sign the last frost is behind us according to an old farmers' saying.

In spring nature adorns us with a palette of green landscapes, called the leaves.

While you and I enjoy the view, leaves are behind the scenes accomplishing some pretty miraculous undertakings.  I'm sure you learned the workings of leaves back in science or biology classes, but if you were anything like me, you retained it just long enough for the exam.

To say that we would not exist without leaves seems a bit drastic but the fact is we depend on plants and the leaves they produce for our survival.

Their green color is the result of various amounts of chlorophyll contained in the leaves. This molecule is busy absorbing sunlight to use as energy and to synthesize carbohydrates from carbon dioxide and water.  Chlorophyll is necessary for plants to take in carbon dioxide and release oxygen, producing the air we breathe. 

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The three major functions* of leaves:

1. Photosynthesis: the process of capturing light energy and converting it to sugar energy (carbohydrates), in the presence of chlorophyll using carbon dioxide from the air and water from the soil

2. Respiration: the process of converting (metabolizing) carbohydrates, with the help of oxygen, to yield energy for growth, reproduction, and other life processes

3. Transpiration: Water in the roots is pulled through the plant’s vascular system by transpiration, which is the loss of water vapor through the stomata (pores) of the leaves. Most of the water exits the stomata, and about 10% is used as an ingredient of photosynthesis.

With that in mind, during hot summer days it's always good to sit in the shade beneath a nice leafy tree. The leaves keep us cool while they continue to do their job.

Leaves come in a huge spectrum of shapes and sizes.  The many different leaves help to distinguish various plant species and are very helpful in plant identification.  Often plants are easy to visually recognize just by looking at the leaves, especially common plants that grow in the region or common leafy greens such as lettuce and parsley or other plants found at the Farmer's Market or grocer.  There have been countless times I've run across plants unfamiliar to me.  It's these times the leaves are very important in helping determine the identity of my mystery plant.  I enjoy using our Plant ID Forum here at All Things Plants. If you ever find yourself stumped, I definitely recommend posting a picture of your mystery plant for identification by our highly skilled members.

A leaf is often classified into two catagories, simple or compound.

Parts of a simple leaf

A leaf with a single blade is called a simple leaf.  Apple trees and grasses are examples of plants with simple leaves.

Axil - Where the petiole of the leaf attaches to the stem.

Blade - The entire broad, flat area of the leaf is the blade.

Margin - The outer edge of the blade is the leaf margin.

Midrib - The main median rib that runs down the center of a leaf or leaflet.

Petiole - A stem-like part of the leaf that joins the leaf blade to the stem of the plant.  Sometimes the petiole is more like a stalk, as is true with celery which has a petiole that is much larger than the stem to which it is attached; the petiole is the part of the celery that we eat.

Stipules - The small leafy outgrowth on either side of the petiole where it attaches to the stem.  The stipules seem to have various functions, some of which are not known.  In some plants, the stipules grow rapidly, enclosing and protecting the blade as it develops.  In others, the stipules produce substances that prevent insects from attacking the blade while it develops.

Veins - Are the vascular tissue that support the leaf, made up of xylem and phloem tubes that transport food, water and nutrients to the plant.

Xylem - Plant tissue consisting of elongated cells that transport water and mineral nutrients.

Phloem - Plant tissue consisting of elongated cells that transport carbohydrates and other nutrients.

Types of blades:

Smooth - An entire margin that is smooth with no indentations.

Divided - Leaves that are actually divided into separate parts, known as leaflets, are referred to as divided leaves.

Lobed - Leaves with indentations that are deep (called sinuses) and large projections (called lobes) that separate into several sections.

Toothed - A leaf edge that has indentations, which can be pointed, wavy, scalloped or jagged like a serrated knife, are all called toothed edge leaves.

 

Scroll your cursor over the images to read the description for some examples.

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COMPOUND LEAVES

A compound leaf consists of two or more separate blades, called leaflets.  Each leaflet can be borne at a single point or at intervals on each side of a petiole. 

Palmate -When the compound leaf with leaflets originate from a single point, they are referred as palmately compound (like fingers of an outstretched hand). 

Pinnate - Compound leaves with leaflets originating from different points along a central stalk are called pinnately compound.

There are many other variations and terms used in a glossary of leaves but this should give you some basic descriptions to go by.

 

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Since this is all about the leaves, it wouldn't seem right if I didn't include the changing of colors.  Leaves begin to fade as the days get shorter; as fall approaches the landscape turns to shades of yellow, orange, red and purple.  When leaves begin to get less light, the amount of chloropyll decreases.  Leaves that turn yellow, orange and brown contain carotenoids which are usually present at all times but are more predominent in the fall.  Red and purple leaves contain anthocyanins produced in the autumn, in response to bright light and excess plant sugars within leaf cells.

 

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EAT AND DRINK SOME LEAVES

Green leafy vegetables are some of the best foods you can put in your body, especially if eaten raw while chlorophyll is still present. 

Eating green leaves will increase the level of oxygen throughout the body.  Chlorophyll found in green leafy vegetables releases carbon dioxide and takes it along with carbon monoxide (the toxic biproducts of our breathing in heat and pollution) and converts them into oxygen.  When more oxygen is present in the body, disease cannot survive; we are healthy. 

There are lots of other health benefits to eating and drinking leafy greens, with no negative side effects, ever. 

Spinach is considered to have some of the highest levels of chlorophyll, as long as it is in its raw state.  Try a spinach salad, spinach dip, or experiment with some blended beverages.

 

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GROW LEAVES INDOORS

By growing leaves indoors you will be growing clean air.  Once again, through the process of photosynthesis houseplants are powerful air cleaners.  While the leaves take in carbon dioxide and release oxygen back into the air, they act like a filtering system that is purifying your home.  Plus, the color green is soothing and helps you relax; it also makes a room look appealing which will lift your spirits.

Keep in mind there are some houseplants that should not be handled and are dangerous to children and pets. Some common examples of toxic houseplants are Amaryllis, Dieffenbachia and Poinsettia.

 

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MORE FUN FACTS

The largest-leaved plants in the entire plant kingdom are two related plants competing for the record-holding title: the raffia palm, Raphia farinifera of the Mascarene Islands and the bamboo palm, R. taedigera of the Amazon basin in South America. The leaf blades have been measured up 65.2 feet (20 meters) and their petioles measured approximately 13 feets (4 meters); with a total leaf length of 78 feet, equivalent to the height of a seven-story building.

The tiniest leaves in the world seem to be up for nomination. Although duckweed is the smallest of any plant species, many lack true leaves. Some of the smallest leaves belong to the common water fern, Azolla filiculoides with leaves that are just 1 mm long. There is a tiny wildflower called pygmy weed, Crassula erecta, also known commonly as stonecrop. It has leaves just 1.3 mm long.

Finding a four leaf clover (namely Trifolium repens) is said to be a rare occurrence and a symbol of good luck.

 

Photo Credits - Please scroll over the images to see the credits.

Photos courtesy of Chelle, Calif_Sue, Horseshoe, Plantladylin, and Wiki Commons.

*Thanks to Larry Rettig for the compilation of the three major functions of leaves.

And a special thanks to my dear daughter-in-law, Falon, who created the inspiration for this article. 

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Comments and Discussion
Thread Title Last Reply Replies
killing a locust tree by galenadogs Sep 15, 2017 3:13 PM 0
fun by lynchdale5 Oct 2, 2015 5:08 PM 0
Many thanks by LarryR Mar 12, 2012 7:26 AM 1
And VERY educational! by crittergarden Mar 7, 2012 5:46 PM 3
fun by vic Mar 6, 2012 5:04 PM 10

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