There are many, many, MANY different structures and behaviors that Aconitum napellus has developed to become better adapted to its environment. Here are I will discuss a few of them.  

Firstly, stomata are a very beneficial adaptation of almost all vascular plants. Stomata are specialized pores that are usually located on the underside of the leaves. This is the main area of gas exchange for the plant, and it helps to solve a variety of issues like desiccation, gas exchange, and even water transport through the plant. Firstly, stomata are surrounded by these special cells called guard cells. These guard cells are what help to decide if the stomata will remain open or closed to the environment. One clever way I remember having these cells described to me is that they are like two of those long-tubular balloons. When they are full of water they expand and pull apart from each other, just like the balloons would do if you filled them with air, meanwhile if they lose water and become flaccid, they come together. This mechanism is how the plant works to prevent losing any unnecessary water loss during times of less rain or lower water levels. When the pores are open the plant is able to get carbon dioxide from the atmosphere for photosynthesis, but as it does this it also loses water. So, if there is a shortage of water the guard cells spend more time in a flaccid state, which keeps the stomata closed. Lastly, the stomata are in a huge way responsible for the transportation of water up the xylem from the roots to the rest of the plant. When the stomata are open and water is evaporating from them a concentration gradient of the water results, which then pulls the water up through the vascular tissue to the top of the plant. This process of evaporation is called transpiration, and it is a large part of what allows plants like Aconitum napellus to grow as tall as they do and still have water at the top of the plant!

The cuticle is another important structural adaptation. This structure is essentially the waxy coating on the outside of plant leaves. This unique tissue is specially designed to help minimize water loss, especially since the leaves are so highly vascularized and have such large surface areas. Without the cuticle the leaf would be able to lose water from all directions, and it would be nearly impossible to regulate. This is extremely important in helping plants keep enough water to function properly.

One of the special adaptations of Aconitum napellus is the specialized poison it produces. This poison is mainly made as an adaptation against predation. To hear more detail about the poison and how it affects the creatures unfortunate enough to come across it (humans included) click on the link here.

Xylem and phloem are another essential adaptation to all vascular plants. To learn more about this type of plant and what makes them different feel free to click here. The xylem and phloem are specialized vascular tissues that help to transport sugars, water, and nutrients all across the plant body. They are primarily located in the stem-regions of the plant, and in A. napellus they are organized into specialized areas called vascular bundles. In A. napellus, along with other eudicots, these bundles are all arranged in a ring near the outside of the plant stem. Each bundle is consists of about half xylem and half phloem tissue. The phloem layer is located on the half of the bundle closer to the outside edge of the stem, whereas the xylem layer takes up the half on the inside.

Phloem is the vascular tissue that transports most of the sugars and nutrients of the plant. (In the picture it is the blue cells on the left). The direction of flow is usually in a downward direction from the leaves (site of photosynthesis) to the roots which are continually growing with the plant. One important thing to recognize, however, is that the flow of material in the phloem is not unidirectional. A.k.a. The flow is not always from up to down. The real rule to follow is that the phloem will always be running from a source (a nutrient rich place) to a sink (a place where nutrients are scarce or being used up very quickly). How the current in phloem is generated is that at the source all of the dissolved sugars and other substances are being actively pumped into the sieve tube members of the phloem against their concentration gradient. Then, in response to the increased solute concentration within the sieve tube members, water flows into tubes causing an increased pressure which pushes the water-sugar mixture down the tube toward the destination. At the sink, the concentration of sugar and nutrients in the cells surrounding the phloem is much lower than those in the tubes, so the solutes diffuse out of the phloem into the surrounding tissues, and the water follows. This creates a negative pressure that also pulls the mixture down the tube to the sink!

Xylem is the tissue in plants that transports water and nutrients that the plant picks up from the soil. (In the picture it is the pink cells on the right). In contrast to the phloem, the xylem generally goes in a down to up direction. The xylem always travels from the roots to the tip of the tree, so if a branch goes off sideways or at an angle the xylem will go along with it. An interesting thing about xylem tissue is that it is primarily dead once it reaches maturity, meaning the cells transporting the water are really just hollow tubes of fiber. Water moves through the xylem through a combination of transpiration, adhesion, cohesion, and tension. As I explained in the stomata paragraph, transpiration is the evaporation of water from the plant through the stomata in the leaves at the top of the plant. This creates a negative pressure for the water which pulls more water upward to take the place of the water that evaporated. Adhesion, cohesion, and tension are all important in the formation of the water column that travels up the xylem. The ability water has to stick to itself and the xylem cell wall keeps the water in a cohesive chain that stays connected all the way from the roots to the leaves of the plant.

As far as movement goes, Aconitum napellus is considered a sessile organism in that it can’t just pick up its roots and walk from one area to the next, but it does have the ability to grow and react to stimuli in different directions.

How does it sense and react to stimuli? Well, rather than using electrical signals like humans do to send their messages from one part of the body to the other, plants such as Aconitum napellus use chemical signals called hormones. Two of the most common hormones in plants are auxin and cytokinin. Auxin is thought to be responsible for a large amount of environmental reactions of the plant, but it largely results in the general lengthening of the plant cells. Cytokinins stimulate division of the plant cells.

What kind of stimulus do plants react to? Well, plants react to many different kinds of stimuli, but three of the most influential are gravity, light, and touch. Gravity causes a response in plants called gravitropism. Depending on what part of the plant you are in, the response to gravity can either be to grow towards (positive gravitropsm) or away (negative gravitropism) from it. It is thought that the concentration of auxin the plant parts are influential in deciding whether a part of the plant will show negative or positive gravitropism. The shoots, with the highest concentration of auxin, generally grow away from gravity, meanwhile the roots with less auxin generally grow toward it.

Light generates a response called phototropism. This response also is closely related to the levels of the hormone auxin in the plant. The light source on any side of the very tip of a plant increases auxin production in that area. Then once the auxin is made it is transported to the opposite side of the plant. The increased auxin levels there causes those cells to grow more and elongate, which in turn bends the plant shoot toward the light!  

Lastly, thigmotropism is the response generated by touch. A good example that our professor, Dr. Volk, is that plants of the same species grown indoors tend to be thinner, taller, and less stable than those grown outdoors. This is because the plant outdoors is responding physically to the environmental pressure of the wind that is not present indoors. The cells of the outdoor plant expend more energy in their cell walls and tend to have a broader, shorter structure than the cells of the indoor plant. As a result, the indoor plant is able to spend more of its energy growing upward which explains why they generally are able to grow taller.

The structures of Aconitum napellus can help to tell the story of how the plant functions. For instance the unique shape of this plant’s flowers are made that way for a reason. The hooded structure is a perfect shape for pollination by a bumblebee. The flower has evolved to a shape that enables it to pass the most pollen possible onto its primary pollinator as the insect feeds on its nectar, resulting in more successful reproduction! To read more about the relationship between A. napellus and the bumblebee or to see an awesome video depicting the two organisms’ interaction with one another click here.

The leaves of A. napellus along with other plants also make a statement about their lifestyle. The thinness of the leaves make it clear that the organism is trying to maximize surface area, in this case t so that it can catch as much light possible for photosynthesis.

Finally, the morphology of the roots of A. napellus are also strongly correlated to their function. All of the different branches and shoots coming from the root help to increase the available surface area. This gives the plant the ability to take in more water and nutrients from the soil. If the root were just one big mass the plant wouldn’t be able to grow nearly as big because it would be impossible to take in enough of its metabolic necessities from soil.

To sum it up, Aconitum napellus has acquired many traits and adaptations to become better suited for its environment and to better react to the signals around it, but that doesn’t mean that it is perfect now by any means. A. napellus along with all other species is constantly evolving to become an even better fit with the world around it, and chances are that it always will be!

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