Training manual - The Vetiver Network International

♦ New roots are developed from nodes when buried by trapped sediment. Vetiver will
continue to grow up with the deposited silt eventually forming terraces, if trapped sediment is not
removed.
4.2 Physiological Characteristics
Like its relatives, maize, sorghum, and sugarcane, vetiver is among the group of plants that
use specialized photosynthesis. Plants employing this so-called C4 pathway, using CO2 more
efficiently than those with the normal (C3 or Calvin Cycle) photosynthesis. For one thing, most C4
plants convert CO2 to sugars using less water which helps them thrive under dry conditions. For
another, they continue growing and “fixing” CO2 at high rates, even with their stomata partially
closed. Since stomata close when a plant is stressed (by drought or salinity, for instance), C4 plant
tend to perform better than most plants under adversity.
The vetiver plant is insensitive to photoperiod and grows and flowers year-round where
temperatures permit. It is best suited to open sunlight and will not establish easily under shady
conditions. However, once established, plants can survive in deep shade for decades. They tolerate
the near darkness under rubber trees and tropical forests, for example (National Research Council
1993).
4.2.1 Physiology of Vetiver Seeds: In a study on the development stages from inflorescence
to florets and seeds, the result indicated that, in optimum condition, seeds can germinate but vitality
is very short. In normal conditions, disarticulation of mature seeds is gradually falling off and seeds
able to germinate only in appropriate condition. Vetiver seeds are sensitive to environmental
factors, hence, easily loose viability. So, there in no need to be concerned about their rapid
distribution and turning into weeds. Due to low viability of vetiver seeds, the germination
percentage is low.
4.2.1.1 Inflorescence: Vetiver has a straight tuft inflorescence, with the main axis
plumose and quite long. The inflorescence and main axis are about 100-150 cm. However, in
healthy individuals it can reach 200 cm. Inflorescence in about 20-30 (maximum 40) cm long, 10-
15 cm broad; the color is purple or violet, which is rather common for the Thai vetiver.
In the Poaceae, the character of inflorescence is very important for identification, but in
vetiver, the traits are easily confused, especially the length, width, and color. Actually, the
inflorescence varies in shape and color according to its developmental stage. There are three stages
as follow:
(1) Anthesis Stage: From emergence from the flag leaf to full blossom, it takes
approximate 4-5 days. At this stage, the main axis elongates very fast. All parts of the inflorescence
are full of water, nutrients, and plant hormones. The gland at the base of rachis is swollen; when
fully turgid, it pushes the rachis to expand. The stamens are reflexed, hanging out from the spikelet,
ready for anthesis.
(2) Post-Anthesis or Embryo-Development Stage: When the spikelet has been
fertilized, the metabolism within inflorescence is decreased gradually. Basal glands will flatten and
the inflorescence will become narrow again. Apical part of the inflorescence is fertilized prior to the
basal part. This stage takes 8-10 days.
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