The Plumeria Root System

The Plumeria Root System

The plumeria root system constitutes a major part of the plant body, both in terms of function and bulk. In plumeria, the root system is the subterranean or underground part of the plant body. Roots are branching organs which grow downward into the soil, a manifestation of geotropism. Branching occurs irregularly and not from nodes as in stems.

In contrast to shoot, the plant root has no leaves, nodes, internodes and buds. With rare exception, roots also lack stomata.

Other morphological and anatomical features which are distinct to this plant structure are: 

  1. a hard, protective root cap at the tip of the root; (2) absence of the pith; 
  2. presence of endodermis; and 
  3. presence of pericycle next to the endodermis.

These features are found in the root apex which is divided into three regions:

  1. region of cell division which includes the apical meristem protected by the root cap,
  2. a short region of cell elongation where individual cells elongate and force the root tip to move forward through the soil, and
  3. region of cell differentiation and maturation.

In general, the plumeria root system either consists of a taproot system (with primary root found on seedlings) or fibrous roots (adventitious roots found on cuttings) with attached branch roots and finer rootlets having root hairs close to the tip.

Functions of the Plumeria Roots

Despite being inconspicuous because they are normally hidden underground, the plant root system performs various functions which are essential to growth and development. The extent of underground expansion of this plant structure serves as limitation in the growth of the plant. Thus potted plants usually exhibit slow growth but once the roots leak out from the bottom of the pot and penetrate into the ground, growth rate accelerates.

The functions of the plumeria root system include:

  1. Anchorage and support. The plumeria root system anchors the plant body to the soil and provides physical support. In general, however, taproot system provides more effective anchorage such that they are more resistant to toppling during storms.
  2. Absorption and conduction. The plumeria root system absorbs water, oxygen and nutrients from the soil in mineral solution, mainly through the root hairs. They are capable of absorbing inorganic nutrients in solution even against concentration gradient. From the root, these are moved upward. Plants with a fibrous root system are more efficient in absorption from shallow sources.
  3. Storage. The root serves as storage organ for water and carbohydrates. Fibrous roots generally store less starch than taproots.
  4. Reproduction. Plumeria do not reproduce from their roots.

Related Images:

Roots and root hairs

Roots are one of the most important parts of the plant for taking up nutrients and water. For some growers, they are so important that they always check the root system before watering.   By Pieter Klaassen CANNA Research 


The foundation


Plants need roots in order to stay upright and not to be blown over by the wind. Water and nutrients also enter the plant through the root system.


The root system will continue to increase in volume for as long as the plant as a whole, including the foliage, continues to grow. When a certain equilibrium has been reached, the plant will simply maintain its volume, and cease to grow. Even in this state of equilibrium, the roots continue to grow, but will die back partly as well. To understand this better, we will have to divide the root system into parts.


The root system


The root systemAs mentioned, the root system will only increase in volume for as long as the rest of the plant continues to grow. However, transpiration from the leaves can also cause more roots to form in order to pump up the water needed. In the end, an equilibrium is established between the roots and the plant. A general rule of thumb is that the root system should comprise 30% of the total plant volume. Although this rule applies fairly consistently to plants in the open air, in substrate culture this does not always have to be the case. You can grow large plants in small pots as long as you supply them with water and nutrients and do not allow the pot to get too dry or too wet. To reduce the chance of this happening, we advise a large medium volume.

In hydro cultures you will also see that fewer roots are needed in order to grow a larger plant. This is because each root hair is able to absorb more water and nutrients. This is one of the reasons that hydro culture has the potential to produce higher yields.


Root hairs

Root hairs
Root tip and a cross section of the root tip

The root hairs are where most of the nutrients and water are absorbed. The root tip produces new cells on a daily basis, and thus also root hairs. When the plant is short of water and/or nutrients, it will devote more assimilates (photosynthesis energy) to producing more cells in the root tip. This also generates more root hairs until the root has found what the plant needs (more water or nutrients). The oldest root hairs will then die off.


In practice, as the medium gets drier, the root starts looking for water and will produce more cells, and thus more root hairs. Absorption capacity increases, because more root hairs are produced. But the youngest root hairs will enter even more “moist” soil. The plant can still take up water and sometimes even more! This is why the general advice is to grow on the dry side: when you water, some of the root hairs become redundant. To limit the energy-loss (dissimilation energy), the oldest root hairs will die off.


If you give the plant too much water, all the root hairs will die off. Effectively, the roots drown and it takes at least three days before a root tip has produced enough new cells with root hairs. The dying off of root hairs also happens after repotting the plants or after moving them very roughly. So when this is the case, go gently on your climate control the first 3 days.
And pay good attention to the watering: don’t overdo it but on the other hand, don’t let the plant dry out too much.


The root


Unlike the root hairs, the roots themselves are visible to humans. The root cells, without root hairs this time, will stretch to enable the propulsion of the youngest part of the root forwards. The outermost cells of the root suberise (form a hard surface, like the bark of a tree), after which they only serve as a pipeline to transport the water and nutrients absorbed towards the stem and the rest of the plant.

Plants in the vegetative phase will increase in weight, both above and below the ground. Even in the first stage of the generative phase, the leaf surface area will increase and an active climate will cause the roots to increase in volume. Eventually, an equilibrium will be reached. This maximum equilibrium usually comes when around 50% to 70% of the flowering period has elapsed (for example, week 6 of a 10-week growing cycle).

In potting mix cultures, the plant can absorb 5 to 6 litres of water/m2 per day. But in hydro cultures more water can be absorbed with fewer root tips (but not fewer root-hairs!).


Root tips


At the end of every root is the root tip. The root tip consists of a root cap and a growing point. The root cap is very hard and protects the growing point. It is so hard, in fact, that it can break and grow through asphalt if the cap has enough energy.


In the growing point behind the cap, new cells are created. The most important plant hormones are also produced here. These will not be discussed in this article. For more information on plant hormones, please see CANNAtalk 9. It is these new cells that cause the roots to grow further through the medium. The roots are able to do this not only because new cells are created, but also because the existing cells are stretched. The first cells also contain bulges, called root hairs.

Related Images:

Root zone temperature and plant health

There are many aspects of crop and plant production that are critical for the success of the effort. One of the most often overlooked and seldom allow ed for aspects of production centers around the temperature of the root zone. After all, it is out of sight and there is not much that can be done about it. Besides, it must be OK to hold the entire plant at the same temperature, right? Wrong; and here is why.