“Plants are all chemists, Tirelessly assembling the molecules of the world.” -Gary Snyder, Introduction, *Pharmako/poeia
Why should you, the aspiring naturalist be concerned with the cellular design of plants? One answer might be – It is in this beautiful design that you will draw closer to plants and their ability to heal humanity. Another reason might be that it is in the cells of plants that knowledge of the evolutionary past and future genetic path are stored. It is also in this knowledge that you will come to know how at risk the earth is because of the efforts of a few who are attempting to genetically modify and capture the cells of plants. The genetic material of cells store the combined ancestral knowledge of plants and no one has a right to destroy our link to our ancestors or our future.
By understanding the cellular structure of plants you will come closer to being able to identify plants very fast and also learn the medicinal, nutritional, utilitarian, and social connection between plants and humans. You will hopefully join the movement to educate yourself about plants and move native plants out of sanctuaries and place them in all our environments. This knowledge was fast slipping from us, now there is a movement to end “plant blindness”.
Come with me on a voyage to learn the basics of plant cellular biology. Before I begin, one story (because I am a Celtic woman – a story at the beginning, a story at the end of each lesson).
A couple of years ago I was very lucky to have spent time with a retired botany professor who loved to teach “newbie’s”- or plant lovers who know very little about plant identification. The man was very patient and had considerable knowledge of plants from my part of the world. He fully understood that when most people go out in the forest they see plants of the same species as pretty much looking all alike One weekend he taught us about conifers. Identification of the many conifers in my part of the world can be quite confusing. They do look somewhat alike. Unless a tree has a very different looking bark or shape it is hard to identify them. That is unless you get very close- I mean on a cellular level of closeness.
Our teacher taught us about cell physiology and plant organelles before we went into the forest. He was especially keen to teach about STOMATA BLOOMS which would allow us to identify many different species of conifers. The stomata are minute pores in a plant organelle in which gas exchange occurs.
A stoma (pl. stomata) is a microscopic pore on the surface (epidermis) of land plants. It is surrounded by a pair of specialized epidermal cells called guard cells, which act as a turgor-driven valve that open and close the pores in response to given environmental conditions.
Carbon dioxide from the atmosphere enters the stomata and oxygen produced by photosynthesis diffuses out of the stomata. Water molecules also escape through the stomata, especially in hot, dry weather. Water loss through the stomata is known as transpiration. If the plant loses too much water it will wilt and eventually die. To cope with this dilemma, plants have evolved paired guard cells on each side of the stoma.
Each tree (plant) expresses the design of stomata blooms differently.
The design and color of the stomata help us plant lovers to more easily identify the plants. For instance the underside of the Western red cedar (Thuja plicata) needles has a butterfly pattern which is actually a stomata bloom. You cannot actually see the guard cells without a microscope, on most plants they’re totally invisible to the naked eye. But you can see the STOMATA BLOOM. Depending on the species and the growing conditions, there are 100-1000 stomata per square millimeter on the underside of a leaf.
Plant cell biology is as complex as human cell biology. Understanding the healthy plant cell physiology can help the naturalist, gardener and plant lover to live closer to the plant world and understand their needs. Understanding this physiology will also keep you from being pulled into the propaganda and lies of big pharma, genetically modified corporates, and other scientists gone mad. There is no easy or fast way to teach you everything there is to know about these cells. So, I am just going to share a few things that I found very interesting about plant cells and plant organelles. Then at the end I will have links so you can further your education in plant cell physiology (blessed be to wiki-links).
CELLS WITH A PURPOSE
Both plants and animals have cells that reflect a genetic purpose. The kindom Plantae purpose IS NOT to take care of humans. Their purpose is to be part of a global interactive, biological, energetic community that cooperates to create balance in all things. This means developing systems of survival.
But as for plant/human cooperation – Plants take CO2 out of the environment and exhale it as oxygen. This important transaction happens both on the cellular and organelle level. This is probably the most well-known reason for plant/human appreciation. We need oxygen to survive. Humans use plants as food because plant cells store nutrients, carbohydrates and chemical compounds that keep us well.
Looking at a plant cell and an animal cell you will see some things are the same, and some things are very different.
At the smallest scale of plant cellular biology are molecular interactions of photosynthesis and internal diffusion of water, minerals, and nutrients. At the largest scale are the processes of plant development, seasonality, dormancy, and reproductive control.
The cells of plants have evolved differently from animals because plants cannot move. Plants defend themselves chemically from herbivores, pathogens, and competition from other plants. Their cellular composition supports these interactions. The cells also produce compounds that defend against disease, permit survival during drought, and prepare plants for dormancy. There are even compounds used to attract pollinators or herbivores to spread ripe seeds. (Yes, we humans are often used by plants to spread pollen and seeds). And in exchange we humans have learned to use those compounds to heal ourselves – as in plant medicine,food and for utility.
I read a couple of research reports on plant plasticity and adaptation some years ago. In these reports scientists and a plant specialist wanted to know how plants interact with threats from herbivores and environmental dangers. They wanted to know if the reaction to threat was immediate or slow-reactive. For a long time scientists and the rest of us saw plants as nonreactive.
In both studies the scientist collected information on plant reaction to threats including humans and found that the reaction happened on the cellular/chemical level and that change was almost immediate. Plants changed their own chemical biology to release bitters, poisons, and chemicals to protect themselves. The plant cells were designed to offer different mechanisms for different situations. This process sometimes also inadvertently caused humans and animals to change physiologically for the better. Human involvement in plant medicine and in some cases mind-altering physical changes have occurred for millions of years. I have listed links to this research at the end of this article.
Plant cells are mostly oblong in shape, animal cells are mostly round Compared to animal cells, plant cell walls are tough. They are strong enough to withstand osmotic pressure. Up to three strata or layers may be found in plant cell walls. Plant cells have a cell wall that restricts the shape of the plant cells and this is what limits its flexibility and mobility. Cell walls in most plant tissues also function as storage depots for carbohydrates that can be broken down and reabsorbed to supply the metabolic and growth needs of the plant.
Up to three strata or layers may be found in plant cell walls:
- The middle lamella, a layer rich in pectins. This outermost layer forms the interface between adjacent plant cells and glues them together.
- The primary cell wall, generally a thin, flexible and extensible layer formed while the cell is growing.
- The secondary cell wall, a thick layer formed inside the primary cell wall after the cell is fully grown. It is not found in all cell types. In some cells, such as found xylem, the secondary wall contains lignin, which strengthens and waterproofs the wall.
For instance the bark of a tree is actually layers of live and dead cells arranged in layers. One layer that lies next to the heartwood of a tree called Sapwood, or xylem, carries water up from the roots to the leaves. As the cells of Xylem age, they turn to heartwood. The next layer out, the cork cambium, covers the tree from twig to root. The cambium which is also called the phellogen, is normally only one cell layer thick and as the cells divides it creates the outer bark layer called cork or phellem. The outer layer of bark on most trees helps keep out water and weather and insects. It acts as an insulation layer and is the product of mass cellular division. The cells of the cork layer produce a substance called suberin, a waxy substance which protects the stem and trunk against water loss, the invasion of insects, and prevents infections by bacteria and fungal spores. Now, understanding this plant cellular biology you probably see why stripping the bark off trees can cause tree death or disease. We humans have forgotten valuable information that would help us to better steward the earth and live harmoniously with plants, especially the great trees.
What is the same and what is different
Both plant cells and animal cells have: Cytoplasm, Mitochondria, Endoplasmic Reticulum (Smooth and Rough), Golgi Apparatus, Microtubules/ Microfilaments, Flagella, and a Nucleus.
In plants the nuclear and cell division are mainly localized in special regions called meristems. This information is important to know if you will be working with seeds, grafting, or hybridization. This rapidly dividing region will either elongate the tips of stems and roots or expand the girth of the plant. In animals, cells divide everywhere, all the time. The division process is essentially the same for plants and animals. The main difference comes when it is time for cytoplasmic division. A plant cell builds a new cell wall to divide its two daughter cells, and an animal cell will pinch in two, or cleave.
Both plant and animal cells have plasma membranes. Plant cells have cell walls; animal cells do not. Plant cells have cell walls in addition to plasma membranes, not instead of plasma membranes. The cell wall of a plant is made from cellulose and is much tougher.
Plant cells have chloroplast for photosynthesis whereas animal cells do not. Animal cells are round whereas plant cells are rectangular. All animal cells have centrioles whereas only some lower plant forms have centrioles in their cells. Plant cells have one very large vacuole in the center and animal cells have a very small vacuole.
Plant cells have both mitochondria and chloroplasts. The chloroplasts turn the sunlight into glucose. The mitochondria turn glucose into energy (ATP).
Plant cells contain chlorophyll, a chemical compound that interacts with light in a way that enables plants to manufacture their own food rather than consuming other living things as animals do.
A plant cell has plasmodesmata – which are narrow channels that act as intercellular cytoplasmic bridges to facilitate communication and transport of materials between plant cells. Plant cells are eukaryotic – A eukaryote is an organism whose cells contain complex structures enclosed within membranes.
“Man sees the morning as the beginning of a new day, he takes germination as the start in the life of a plant, and withering as its end. But this is nothing more than biased judgment on his part. Nature is one. There is no starting point or destination, only an unending flux, a continuous metamorphosis of all things.”
- Masanobu Fukuoka, The Natural Way of Farming
Cells alive – interactive animal and plant cell website – http://www.cellsalive.com/cells/cell_model.htm
Differences between plant and animal cells – http://wiki.answers.com/Q/Differences_between_animal_and_plant_cells#ixzz1lqkl5zMS
Biology online: a site to teach you biology, botany, cellular biology and other useful biological and botanical science. http://quizlet.com/5551829/biology-test-1-flash-cards/
Plant cell physiology – http://en.wikipedia.org/wiki/Plant_cell viewed on the internet 2/7/2012
Karban, Richard, Agrawal, Anurag A., Thaler, Jennifer S. and Adler, Lynn S.. Induced plant responses and information content about risk of herbivory, Tree – Ecology and Evolution vol. 14, no. 11, pages 83-86 November 1999
Buhner, Stephen Harrod, (2002) The Lost Language of Plants: The Ecological Importance of Plant Medicines to Life on Earth, Chelsea Green Publishing, White River, VT
- Organelles – mean little organs. They are located inside the cell structure and have specific roles to play in how cells work.
- stoma (pl. stomata) is a microscopic pore on the surface (epidermis) of land plants. It is surrounded by a pair of specialized epidermal cells called guard cells, which act as a turgor-driven valve that open and close the pores in response to given environmental conditions.
- Turgor – Turgor pressure pushes the plasma membrane against the cell wall of plant, bacteria, and fungi cells as well as those protist cells which have cell walls.
- A vacuole is a membrane-bound organelle which is present in all plant and fungal cells and some protist, animal and bacterial cells. Vacuoles are essentially enclosed compartments which are filled with water containing inorganic and organic molecules. They have multi-functions including:
- isolating materials that might be harmful or a threat to the cell,
- holding and exporting waste products
- contain water in plant cells
- Maintaining internal hydrostatic pressure or turgor within the cell
- Maintaining an acidic internal pH
- Containing small molecules
- Exporting unwanted substances from the cell
- Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole
- In seeds, stored proteins needed for germination are kept in ‘protein bodies’, which are modified vacuoles.
Daggawalla seeds and herbs. Open pollinated seeds and many specialized herbs.