Research topics of applying Vetiver for carbon sequestration in Taiwan

The global warming is becoming an urgent issue around the world beyond the scientific domain. The carbon sequestration is one of the active means by reducing carbon dioxide in the atmosphere. The massive root system of vetiver has present itself to the scientists as an effective candidate for storing the captured carbon into the less disturbed deep soil profile as an alternative to the trunk of tree.

The global warming bright two impacts on plants: elevation of the ambient temperature and higher concentration of atmospheric carbon dioxide. Both temperature and concentration of CO2 impact differently on species as well as varieties (genotypes). Will the current vetiver variety continue to contribute to the carbon sequestration when the temperature and/or CO2 concentration deviated significantly from now? And what is the magnitude of deviation shall be considered significant.

In our lab in the Department of Agronomy, National Taiwan University has addressed many of these issues since 1998 after receiving representing germplasm from Dr. Robert Adams. In the beginning of the research of vetiver limited by the available germplasm and plant materials, the genotypes been evaluated may not be the best representation of the vetiver germplasm. Nonetheless, the results certainly provided some clues for later studies. The following is some results from previous studies conducted in our lab.

 

Growth response to elevated temperature

The study was conducted in the phytotron under 35/30, 30/25, 25/20, 20/15 and 15/13ºC day/night temperature without light supplement using three genotype Ohito, Taiwan and VVZ008-18 (selected genotype from seedy vetiver germplasm). The root extension rate was recorded and found that the trend of the growth curve corresponds to the temperature showed that the rate of root extension reaches a plateau at 25ºC, although 35ºC treatment shown highest extension rate on average without statistical significance (Fig. 1).

The extreme of the high temperature before vetiver dormant or damaged was not studied in the study.

 

Fig. 1. The effect of temperature on the root length of vetiver. Three genotypes of vetiver: VVZ008-18, Ohito, and Taiwan were included in this study. Five temperature treatments: 15/13, 20/15, 25/20, 30/25, and 35/30ºC were applied to the three genotypes. The vertical bars represented the root length of each genotype at each temperature treatment in day 24. The line indicated the average length of the three genotypes.

 

Rate of Photosynthesis response to elevated CO2 concentration

After the genetic diversity of vetiver been evaluated using RAPD and AFLP marker system, seven genotypes were selected as representatives of the vetiver germplasm for conducting the study.

The photosynthetic rate was measured using LI-COR LI-6400 machine using 365 ppm CO2 (current atmospheric concentration), 450, 500, 600 and 700 ppm CO2. The plant

Vetiver photosynthetic rate measured by LI-6400。

	CO2 Concentration(ppm)
Vetiver varieties	365 (current value)	450	500	600	700
VVZ009	*21.63	29.00	57.56	116.80	144.65
VVZ010	25.70	33.64	61.28	86.26	100.96
VVZ014	21.44	33.49	59.83	88.50	104.94
VVZ017	28.57	38.39	69.42	107.01	116.84
VVZ021	26.01	42.55	64.23	101.52	111.90
VVZ022	31.37	42.82	72.68	90.41	118.65
VVZ024	31.03	49.19	73.25	91.88	118.12

*The numeric value was average of five vetiver plants.

The photosynthetic rate showed a linear increase with the elevated CO2 concentration. The varieties response differently to the elevation of CO2 concentration in terms of rate of increase, which implied a selection of variety should be considered in order to maximize the effectiveness of CO2 absorption.

The partition of the biomass into the root (underground) and tillers (above ground) of the selected genotypes was also measured and the results indicated a variation of the genotypes. VVZ024 distributed the photosynthates about equally to both above and underground biomass, VVZ021 had more of its photosynthates distributed to the underground biomass and VVZ009 distributed more to the above ground biomass.

The results should provide an evidence for vetiver as:

1.     an effective CO2 absorber even in twice the CO2 concentration of current level.

2.     An effective carbon sequestrator for depositing its biomass underground.

3.     An effective bio-energy feedstock for distributing more of its biomass aboveground.

 

The biomass production potential of vetiver

The vetiver was using as erosion control plant for most of the users. The production of biomass was not much interested to them. As vetiver moving toward the application of carbon sequestrator, its potential for producing biomass for the use as feedstock for biofuel and/or carbon sequestration should be studied and exploited. A project conducted on 2001 to evaluate the breeding potential of vetiver had revealed a great diversity of the biomass yield between genotypes, the fresh weight of plant from individual seeds grown for one year was ranging from 77 to 8,300gm. Although scattered pieces of biomass production information were obtained from several previous studies, a new project is currently underway with all the acquired germplasm and several selected genotypes from several half-sib families.

 

 

Yue-Wen Wang, Ph.D.

Grassland Laboratory

Department of Agronomy

National Taiwan University