Tag Archives: Botany

How Water Travels Through a Plant

The Garden Artist Posted on by

When we need to “Water” ourselves we take a drink towards the top of our stem, our mouth.

This water, sooner or later is then is eliminated, as if by gravity below the point of entry.

Plants, on the other hand, take a drink at the very bottom of their structure, their roots, and then, defying gravity, eliminate the excess at the very top of their structure, their leaves.

How is this journey accomplished?

Pathway of Water Through a Plant

  1. Water enters the plant through the root hairs.
  2. It is then conducted upward in the stem via the xylem.
  3. Water exits the plant through the stomata located on the leaves.

 

Osmosis is the process used for the water to enter the root hairs.

Cohesion-tension theory is believed to be the method that water is conducted upward via the xylem. Think of adjacent drops of water, which when their exterior barriers are broken, move & merge into one larger drop.

Transpiration is the process of water evaporating from the leaf.

Roots have microscopic root hairs to take up more water

Roots have microscopic root hairs to take up more water

Roots

At the root of it all…are the roots.

Roots are designed in different ways to anchor plants.

Their main purpose, however, is to gather from the soil the water & nutrients needed to sustain & grow the plant.

To do this the root is designed in a point called the apical meristem.

This apical meristem pushes through the soil in search of nourishment.

In order to increase the surface for absorption the root has microscopic root hairs that increase the surface several hundred times. By osmosis, these root hairs bring water into the root.

Osmosis is the process that allows water to pass through cell epidermal walls.  Water molecules attempt to balance the amount of water pressure on either side of the wall. Once the water enters the root hairs the equalizing mechanism is shut down & the water can’t escape. It then moves from the root hairs to the roots via a process called turgor.  

Stem

Water moves through the plant from roots to leaves through the xylem. Osmosis moves the water from the ground to the root systems & cell turgor moves the water through the xylem.

Cell turgor is what keeps the firmness in plants. With low turgor you get wilting. You want to keep all cells filled with water or the cells begin to die.

This is why you cut flowers under water to use in your flower arrangement.

To protect the cells from exploding with too much water as it moves from the roots to the xylem, the cell walls protect themselves by pushing the water out into the hollow tubular cells in the root’s center using a gentle pumping action called root pressure. This brings the water into the xylem, which now conducts the water upwards from the roots to the leaves.

Transpiration

Rhododendron leaves in winter.

Rhododendron leaves in winter will curl up to reduce the number of stomates on exposed surfaces to reduce the transpiration rate of water. In my garden the rhodi leaves curl when the temperature moves into the 20’s

Transpiration occurs in the leaves by way of the stomates usually located on the underside of the leaves. Water is vaporized through the stomates & is replaced by liquid water that has been delivered by the continuous flow upwards through the xylem system of roots, stems and leaves.

This transpirational pull is felt throughout the entire length of the plant.

In most plants about 98% of the water is lost through the transpired water vapor from under the leaves. A 48-ft tall Silver Maple is thought to transpire up to 58 gallons of water an hour.

You can perceive this on a hot summer day when sitting under a large shade tree & enjoying the cooling effects of the transpired water.

Stomates

Plants protect themselves from too much loss of moisture by closing the stomates in the underside of the leaves. Generally, stomates are open during the day & close in the night-time. In the winter when the ground freezes you can see the curled leaves of large leaved rhododendrons as they reduce the available surface of exposed stomates.

In preparation for winter and in times of drought, leaves will fall from the trees in a process called abscission further reducing the stomatic surfaces used for transpiration.

Cold Hardening

Colocasia after the first frost

In winter, the deciduous trees have lost their leaves and water movement halts. If the water freezes in the cells, it ruptures the cell membranes. You can see this quickly in Colocasia AKA Elephant Ears after the first cold snap.

One way that winter-hardy plants survive is by a process of cold hardening, which uses sugars that function somewhat like antifreeze.

The pathways for water distribution are also modeled for nutrient distribution in the plants but that is worth another entire post.

 

What is a Corm and How Is It Propagated?

The Garden Artist Posted on by

CORMS

Corms look a lot like bulbs on the outside but they are quite different. They have the same type of protective covering and a basal plate like the bulb does, but do not grow in layers.

Instead, the corm is the actual base for the flower stem and has a solid texture. As the flower grows, the corm actually shrivels as the nutrients are used up. Essentially the corm dies, but it does produce new corms right next to or above the dead corm. It has contractile roots that bring down the corms as they rise up to the surface of the soil which is why the flowers come back year after year. Depending on the type of flower, it may take a couple years to reach blooming size.

A corm does not have visible storage rings when cut in half. This distinguishes it from a true bulb.

Photo of the corms of a colocasia and a crocus by the Artist, Mary Ahern

Corms of a dormant colocasia (Elephant Ears) and a crocus in bloom.

CORM ROOTS

Many corms produce two different types of roots. Those growing from the bottom of the corm are normal fibrous roots, they are formed as the shoots grow, and are produced from the basal area at the bottom of the corm. The second type of roots are thicker layered roots that form as the new corms are growing, they are called contractile roots and they pull the corm deeper into the soil. They are produced in response to fluctuating soil temperatures and light levels. Once the corm is deep enough within the soil where the temperature is more uniform and there is no light, the contractile roots no longer grow and the corm is no longer pulled deeper into the soil.

PROPAGATING CORMS

The newly dug corms will have cormels that are pea size formed around the top of the old corm. The remains of the old corm will be directly beneath the newly formed corms. When the corm is cleaned up and the old stem removed, the growing point of the corm will be evident. The cormels can be saved and replanted in the back of the garden until they reach flowering size.

Examples of Hardy Corms – Crocus. Arisaema, Crocosmia, Liatris

Examples of Tender Corms: Gladiolus, Colocasia, Alocasia, Bananas (Musa), Ensete, Taro, Xanthosoma

 

Allium bulgaricum

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Allium bulgaricum in the garden that inpired the artist, Mary Ahern

Allium bulgaricum

Sometimes the most fascinating aspect of a flower is before it even arrives. I love to watch the progressive morphing of the Allium bulgaricum as it pushes through the ground early in my perennial bed, usually before I’ve even managed to clean off the winter debris.

These tall, 36″ stalks are very strong and have never needed staking. These particular bulbs have been living in my garden since 2003 after I bought them at an after-season sale at Home Depot. I always scour the sales in various Home Depot stores in my area to capture the treasures left behind by the undiscerning customers.

Allium bulgaricum breaking through the tunicate. In the garden that inspires the artist, Mary Ahern

Allium bulgaricum breaking through the tunicate.

As the flower grows you can see it bulging through the paper thin protective membrane covering.

I walk daily through my perennial bed waiting for the first tear in the parchment like shield. I would liken it to the first beak marks I’ve seen when a chick is breaking out of it’s shell. Not that I’ve seen chicks very often since I was raised in Brooklyn, which is not noted for farmland.

Allium bulgaricum stretching it’s wings in the garden that inspires the artist, Mary Ahern.

Allium bulgaricum stretching it’s wings

The flowers pounce forth in a gleeful display of empowerment and spread their wings in umbel fashion sitting proudly on tall stalks overlooking a still short, unfolding and early season perennial garden. These are not glamorous flowers in my opinion but they always add weeks of drama to my early spring theater.

Allium bulgaricum in full bloom in the garden that inspires the artist, Mary Ahern

Allium bulgaricum in full bloom

 

Thanksgiving Pie Facts

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Here are some tidbits of information about some of American’s favorite pies.

PumpkinsPumpkin Pie

Pumpkins are vining annual plants that are part of the Cucurbitaceae or Cucumber family. They are actually winter squash named Cucurbita pepo with the oldest pumpkin related seeds found in Mexico dating back to between 7000 & 5500 BC.

Pumpkins are grown on every continent except Antarctica but the traditional American pumpkin that we are familiar with is the Connecticut Field variety. Pumpkins produce both male and female flowers on each vine and are pollinated by honey bees.

Red Apple Apple Pie

Apples are formally named Malus domestica and they are from the rose family of Rosaceae. The fruit is a pome, which is characterized by one or more carpels surrounded by accessory tissue. This tissue is the edible part and is useful in protecting the buried seeds.

Apple trees were widely planted and seeds distributed by John Chapman who became known as “Johnny Appleseed”. This wide distribution of open pollinated seed helped to widen the choice of available cultivars in early America to over 8,000 of which 100 are grown commercially today.

Ipomoea batatas - Sweet PotatoesSweet Potato Pie

Ipomaea batatas or sweet potatoes belong to the Convolvulaceae family. It is an herbaceous perennial vine, with an edible long and tapered tuberous root. Though distantly related to the potato in the Solanum tuberosum family, it is not a nightshade plant. It was domesticated over 5,000 years ago in either Central or South America but is the staple food for many countries worldwide.

For most of American history sweet potatoes were an important part of the diet but fell out of favor as people became more affluent during the middle of the 20th century. There has been a resurgence of popularity with the awareness of the rich dietary contributions offered by this humble plant.

Life is uncertain, Eat Dessert First!

Disclosure: Facts were gathered from the internet especially Wikipedia.