RESPONSES OF Jatropha curcas L. TO WATER STRESS

Kevin Muyang Tawie Anak Sulok

Master of Science 2010

Pusat Khidmat ýtilaklumat Akydemik llNIVEItSITI MALAYSIA SARAµAK

Responses of Jatropha curcas L. to Water Stress P. KIiIDMAT MAKLUMAT AKADEMIK

111111111pril 111111111 1000246274

KEVIN MUYANG TAWIE ANAK SULOK

A thesis submitted in fulfillment of the requirement for the degree of

Master of Science

Faculty of Resource Science and Technology UNIVERSI TI MALAYSIA SARAWAK

2010

To Dad, Sulok Tawie

Mom, Agnes Tiong,

Beloved Brother and Sisters, Jeffrey, Sharon, Priscilla and Steffi

Thank you for your love and support

Special Thanks to Eunice Herbert

ACKNOWLEDGEMENTS

I am grateful to the Lord Almighty for His grace, blessings, and the strength

granted to me to complete this study. I would like to express my sincere appreciation and

gratitude to Dr. Siti Rubiah Zainudin, for her supervision, guidance, support, and

tolerance throughout this study. Her understanding and patience in this study were most

comforting.

I am also grateful to Prof. Dr. Wan Sulaiman Wan Harun who supervised and

guided me earlier in this study. I would also like to acknowledge the contribution made

by Dr. Kamarul'Ain Mustafa, Prof. Dr. Zin Zawawi Zakaria, and Dr. Affendi Suhaili for

their meticulous and constructive comments on the dissertation.

Special thanks to all the staff at Faculty of Resource Science and Technology,

UNIMAS, especially Mr. Leo Bulin and Mr. Rajuna Tahir for their assistance. I also wish

to extend my appreciation to Miss Roberta Lee of Roberts Scientific Sdn. Bhd., Mr.

Johnny Lee of Syarikat Alam Widuri Sdn. Bhd., and the Soil Branch of Department of

Agriculture, Sarawak for providing me with the proper materials and info for my study.

Thank you so much to all my friends Norizan Sebri, Adel-Aisyadil, Nabihah

Hamdan, Fitzpatrick Ricky, Norman Shane, and Ismadi Rosli for their help in one way or

another also aided in the successful completion of this study.

11

ABSTRACT

C Research on production of Jatropha curcas focus mainly on its suitability to dry and and

lands; whereas less attention has been paid to its production under high water availability.

The growth performance of a drought tolerant plant such as J. curcas under different

watering regimes was studied to investigate the influence of both high and reduced water

availability on the various morphological and physiological traits that could contribute to

an understanding of the effects of water stress on the plant. The experiment was a

completely randomized design (CRD) with 4 treatments replicated 3 times )Each replicate

consisted of 2 plants with a total of 24 plants altogether. Treatments were: (i) Rainfed

(WO) - Plants watered at field capacity > -0.03 MPa, (ii) Mild water stress (W1) - Water

maintained at soil water potential between > -0.10 and > -0.30 MPa, (iii) Moderate water

stress (W2) - Water maintained at soil water potential between > -0.80 and > -1.0 MPa,

and (iv) Extreme water stress (W3) - Water maintained at soil permanent wilt point >-

1.50 MPa. The well-watered plants responded by showing significantly (p < 0.05) better

height, greater proportion of inflorescence and fruits, comparatively larger fruits and

more mass in seeds, higher leaf stomatal density and bigger leaf area growth. Number of

inflorescences, amount of fruits, fruit size, seeds mass, and leaf stomatal density were

increased by 31,54,90,3, and 69 % respectively in plants grown under well-watered

conditions. Photosynthesis rates (A), stomatal conductance (gs), and transpiration (E) of

the control was significantly (p < 0.05) higher than its water-stressed counterparts.

However, water use efficiency for WO and W3 showed insignificant difference probably

due to W3 adaptive capability to water deficits. Strong correlations were established

between leaf stomatal conductance with both photosynthetic rates (r2 = 0.86) and

volumetric soil water content (r2 = 0.89). Furthermore, foliar abscisic acid (ABA) was

significantly correlated to stomatal conductance (r2 = 0.96) and volumetric soil water

content (r2 = 0.83). Extreme water stress increased foliar ABA by 5-folds which in turn

reduced stomatal conductance and thus decreasing photosynthesis rates. As an indicator

for water stress, foliar spectral analysis showed low reflectance which attributed

primarily to absorption by higher concentration of chlorophyll photosynthetic pigments

and the presence of cytoplasmic fluid at the leaf cellular level. Strong significant

I11

correlations were achieved by the reflectance indices such as the reflectance at 550 nm (R550), structure independent pigment index (SIPI), and photochemical reflectance index

(PRI) to leaf photosynthetic pigments indicating the depression caused by drought to

chlorophyll concentrations in leaves. Overall, the well-watered plants at soil water field

capacity (-0.03 MPa) showed better morphological and physiological responses whereby

the positive effect has been very favaourable in terms of its flowering and fruiting due to

the plant's potential to produce biofuel.

Key Words: Jatropha curcas, soil physics, soil chemistry, water stress, plant

morphology, photosynthesis, ABA, chlorophyll

iv

Respon Jatropha curcas L. Terhadap Kekurangan Air

ABSTRAK

Kajian mengenai pengeluaran Jatropha curcas hanyafokus kepada kesesuaiannya pada

tanah yang kering dan kontang; tetapi kurang perhatian terhadap adaptasinya kepada

kewujudan air yang banyak. Prestasi pertumbuhan tanaman tahan kemarau seperti J.

curcas dalam pelbagai peringkat rejim air dijalankan untuk mengkaji pengaruhnya ke

atas pelbagai ciri morfologi dan fisiologi supaya dapat menyumbang kepada pemahaman

tentang kekurangan air kepada tumbuhan. Eksperimen adalah completely randomized

design (CRD), mempunyai 4 rawatan yang direplikasi 3 kali. Setiap replikat mempunyai

2 pokok dan memberi jumlah nilai kesemuanya 24 pokok. Empat rawatan itu adalah: (i)

Kawalan (WO) - Tumbuhan menerima air pada kapasiti tanah > -0.03 Mpa, (ii) Stres air

yang sedikit (WI) - Potensi air tanah dikekalkan antara > -0.10 dan > -3.0 Mpa, (iii)

Stres air sederhana (W2) - Potensi air tanah dikekalkan antara > -0.80 dan > -1.0 Mpa,

dan (iv) Stres air ekstrem (W3) - Potensi air tanah dikekalkan pads -1.50 Mpa. Tanaman

yang menerima air yang cukup memberi respon yang signifikan (p < 0.05) di mana is

menunjukkan ketinggian yang lebih, lebih banyak bunga dan buah bush yang lebih

besar and biji yang lebih berat, kepekatan stomata daun yang lebih banyak, dam kawasan

daun yang lebih luas. Bilangan bunga, bilangan buah, saiz buah, berat buah, dan

kepekatan stomata daun masing-masing mengalami peningkatan sebanyak 31,54,90,3,

and 69 % dalam pokok yang menerima air yang cukup. Kajian menunjukkan kadar

fotosintesis (A), konduksi stomata (gs), dan transpirasi (E) bagi pokok WO memberi

peningkatan yang signifikan (p < 0.05) berbanding yang mengalami stres air. Namun,

WUE bagi WO and W3 menunjukkan tidak signifikan mungkin disebabkan keupayaan

adaptasi W3 terhadap kekurangan air. Hubungan yang kukuh antara kadar fotosintesis

(r2 = 0.86) dan air tanah (r2 = 0.89) dengan konduksi stomata daun. Tambahan,

kandungan ABA dann adalah berkait secara signifikan dengan konduksi stomata (r2 =

0.96) dam air tanah (r2 = 0.83). Kekurangan air meningkatkan kandungan ABA daun

sebanyak 5 kali yang seterusnya mengurangkan konduksi daun dan kadar fotosintesis.

Sebagai indikator kekurangan air, analisis spektral daun menunjukkan pantulan yang

V

rendah disebabkan penyerapan oleh kepekatan pigmen fotosintesis klorofil yang tinggi

dun kewujudan cecair sitoplasma dalam sel daun. Hubungan yang kukuh didapati antara

kaedah-kaedah seperti Rssg SIPI, dan PRI dengan pigmen fotosintesis daun menunjukkan

tekanan yang disebabkan oleh kemarau kepada kepekatan klorofil daun. Kesimpulannya,

tanaman yang menerima air yang cukup memberi respon morfologikal danfisiologikal

yang lebih baik dan ini memberi kesan positif dari segi penghasilan bunga dan buah

disebabkan oleh potensi tumbuhan ini untuk menghasilkan minyak.

Kata Kunci: Jatropha curcas, fizik tanah, kimia tanah, kekurangan air, morfologi

tumbuhan, fotosintesis, ABA, klorofil

V1

Dedication Acknowledgements Abstract Abstrak Table of content List of Tables List of Figures Abbreviations

Chapter 1:

1.1 1.2 1.3 1.4 1.5

Chapter 2:

2.1 2.1.1 2.2 2.2.1 2.3 2.4 2.4.1 2.4.2 2.4.3 2.4.4 2.5 2.6 2.6.1 2.6.2 2.6.3 2.6.4 2.6.5 2.7 2.7.1 2.7.2 2.7.3 2.8

t'usat Ktºidnºat Maklumat AKauri,,:.. UPIIVERSTfI MALAYSIA SARAWAI(

TABLE OF CONTENT

Page

11

111

V

V11

R

xi

xiv

Introduction

Background 1 Biofuel production in Malaysia 2 Responses and adaptations to drought 4 Preliminary study on J. curcas in Sarawak 5 Problem statement 6

Literature Review

Jatropha curcas Linn. 8 Botanical description of J. curcas 9 Cultivation of J. curcas 11 Flowering and pruning of J. curcas 12 Seed oil content and quality of J. curcas 14 Growth requirement of J. curcas 15 Climate 15 Water 16 Light response 18 Nutrient 20 Effect of drought on plant growth 21 Morphological response of plants to drought 23 Shoot growth 23 Root growth 24 Root-shoot ratio 27 Leaf area index (LAI) 28 Leaf stomatal density 31 Physiological response of plants to drought 32 Photosynthesis 32 Stomatal conductance 36 Chlorophyll 38 Foliar spectral reflectance 40

Vii

2.8.1 Water stress estimation 40 2.8.2 Chlorophyll absorption 42 2.9 Role of abscisic acid (ABA) in plant 43 2.10 Soils physical properties 47 2.10.1 Soil texture 47 2.10.2 Soil bulk density 47 2.10.3 Soil porosity 47 2.10.4 Soil available water content 48 2.11 Soil characteristics 48 2.11.1 Triboh series 48 2.11.2 Horizon description 49 2.11.3 Range in characteristics 49 2.11.4 Principal associated soils 50

Chapter 3: Methodology

3.1 Study site and seeds source 51 3.2 Experimental soil 52 3.3 Experimental design and treatments 52 3.4 Rainfall data 54 3.5 Soil water characteristics 54 3.6 Soil chemical properties 56 3.7 Morphological measurements 57 3.7.1 Plant growth measurements 57 3.7.2 Seed mass 57 3.7.3 Leaf area index (LAI) 58 3.7.4 Leaf stomata density 58 3.8 Physiological measurements 59 3.8.1 Gas exchange measurements 59

3.8.2 Foliar ABA concentration 60

3.8.2.1 General experimental procedure 60 3.8.2.2 Preparation of TLC 61

3.8.2.3 Preparation of CC 61

3.8.2.4 Leaf collection and extraction procedure 62

3.8.2.5 High performance liquid chromatography (HPLC) 63

3.8.3 Foliar spectral reflectance 65

3.8.4 Chlorophyll measurement 67

3.9 Statistical analysis 67

Chapter 4: Results

4.1 Rainfall 68

4.2 Soil water characteristic 68

4.3 Soil chemical properties 69

4.4 Volumetric soil water content 70

4.5 Morphological responses 71

viii

4.5.1 Growth parameters 71 4.5.1.1 Plant height 71 4.5.1.2 Stem circumference 72 4.5.1.3 Number of inflorescence 73 4.5.1.4 Number of fruits 74 4.5.1.5 Fruit diameter 75 4.5.1.6 Seeds mass 77 4.5.2 Leaf Area Index (LAI) 78 4.5.3 Leaf stomatal density 81 4.6 Physiological responses 83 4.6.1 Gas exchange measurements 83 4.6.1.1 Leaf photosynthesis rate (A) 83 4.6.1.2 Leaf transpiration rate (E) 84 4.6.1.3 Water use efficiency (WUE) 86 4.6.1.4 Leaf stomatal conductance (gs) 87 4.6.1.5 Relationship between photosynthesis rate (A)

and stomatal conductance (gs) 89 4.6.1.6 Relationship between stomatal conductance (gs)

and soil water content 89 4.7 Foliar ABA concentration and stomatal

conductance 91 4.7.1 HPLC analysis for ABA determination 91 4.7.2 Relationship between foliar ABA and volumetric

SWC 95 4.7.3 Relationship between stomatal conductance

and foliar ABA 96 4.8 Foliar spectral reflectance 97 4.8.1 Chlorophyll absorption 97

Chapter 5: Discussion 102

Chapter 6: Summary and Conclusions 115

References 118

Appendices

ix

LIST OF TABLES

Table Page

Table 1 Leaf gas exchange rate responds of different drought tolerant plants to water stress .........................................................................

33

Table 2 Yearly trend of cotton (Leaf Area Index, LAI) and chlorophyll index averaged as affected by soil water content (%) across a research site in Mississippi in 1987 - 1988 .........................................................

40

Table 3 Triboh series chemical properties ............................................... 49

Table 4 Triboh series physical properties ................................................ 49

Table 5 Different levels of water regimes established by watering and withholding exposure to rainfall ...................................................

53

Table 6 Soil water characteristics of Triboh series before planting ..................... 69

Table 7 Soil chemical properties of Triboh series before planting .......................... 69

Table 8 Effect of different water regimes on J. curcas abaxial leaves stomatal density

.............................................................................. 81

Table 9 Effect of different water regimes on various J. curcas physiological measurements at noon during April, July, and October 2009

............... 85

Table 10 Regression equations for selected gas exchange measurements of J. curcas .............................................................................

91

Table 11 Percentage yields from J. curcas leaf extracts after column chromatography ....................................................................

91

Table 12 Fractionation and analysis using CC and TLC of J. curcas leaf extract

and standard ABA ..................................................................

92

Table 13 Effect of different water regimes on J. curcas foliar ABA concentration and leaf stomatal conductance measured in the month of July 200.......... 95

Table 14 Effect of different water regimes on J. curcas leaves relative chlorophyll content .................................................................................

99

Table 15 Regression equations for reflectance measurements versus foliar relative chlorophyll content of J. curcas leaves .............................................

101

X

LIST OF FIGURES

Figure Page

Figure 1 Important parts of J. curcas ...................................................... 10

Figure 2 Structure for phorbol esters ....................................................... 14

Figure 3 Light response curve of J. curcas L. in a nursery and in plantation compared to other tropical plant species in Belize

............................ 19

Figure 4 Structure of abscisic acid (ABA) ..................................................

43

Figure 5 Structure for indole-3 -acetic acid (IAA) ........................................

46

Figure 6 The water-stressed J. curcas seedlings planted at the Ebung A, Kota Samarahan, Sarawak study site ...................................................

54

Figure 7 Relationship between the peak areas obtained from the HPLC and concentration of ABA standards .................................................

65

Figure 8 Monthly cumulative daily rainfall recorded from October 2008 to October 2009

........................................................................ 68

Figure 9 Volumetric soil water content at a soil depth of 0-15 cm from October 2008 to October 2009 recorded at the study site ...............................

71

Figure 10 Effect of water regimes on J. curcas height with time ......................... 72

Figure 11 Effect of water regimes on J. curcas circumference of stem with time..... 73

Figure 12 Effect of water regimes on J. curcas number of inflorescence with time ....................................................................................

74

Figure 13 Effect of water regimes on J. curcas number of fiuit with time .............. 75

Figure 14 Effect of water regimes on J. curcas diameter of fiuit with time ............. 76

Figure 15 Comparison between control, mild, moderate, and extreme

water-stressed fruits .................................................................

77

Figure 16 Effect of water regimes on J. curcas seed mass (g) with time .................. 78

Figure 17 Effect of water regimes on J. curcas leaf area index (LAI) with time........ 79

R1

Figure 18 Comparison between control, mild, moderate, and extreme water-stressed leaves

............................................................... 80

Figure 19 Morphological images of the J. curcas leaves subjected to different level of water stress ........................................................................

82

Figure 20 Diurnal changes of mean J. curcas leaf photosynthesis (A) rate under different levels of water regimes measured in the month of April, July, and October 2009

................................................................... 84

Figure 21 Diurnal changes of mean J. curcas leaf transpiration rate (E) under different levels of water regimes measured in the month of April, July, and October 2009 ................................................................... 86

Figure 22 Diurnal changes of mean J. curcas leaf water use efficiency (WUE) under different levels of water regimes measured in the month of April, July, and October 2009

................................................................................. 87

Figure 23 Diurnal changes of mean leaf stomatal conductance (gs) to water vapour in J. curcas under different levels of water regimes measured in the month of April, July, and October 2009

.................................................. 88

Figure 24 Relationship between leaf photosynthesis rate (A) and stomatal conductance (gs) in J. curcas subjected to different levels of water regimes ................................................................................ 90

Figure 25 Relationship between leaf stomata! conductance (gs) and volumetric soil water content (%) in J. curcas subjected to different levels of water regimes ................................................................................ 90

Figure 26 Chromatogram of standard ABA (2.0 mg/L) obtained on a Lichrospher 100 RP-18 E column .............................................................................. 94

Figure 27 Retention time (min) for ABA peak from each extract, 1" unknown peak, and 2nd unknown peak obtained using reversed-phase HPLC analysis....... 94

Figure 28 Relationship between foliar ABA concentration and volumetric soil water content (%) in J. curcas subjected to water stress during the month of July 2009 ........................................................................... 96

Figure 29 Relationship between leaf stomatal conductance and foliar ABA concentration in J. curcas subjected to water stress during the month of July 2009 ............................................................................... 97

X11

Figure 30 Mean laboratory spectral reflectance of J. curcas leaves under different water regimes at wavelengths ranging from 400 - 800 nm .....................

98

Figure 31 Relationship between several reflectance indices (8550, SIPI, and PRI) and relative chlorophyll content (SPAD) in Jatropha curcas leaves subjected to water stress ............................................................. 100

X111

ABBREVIATIONS

A

ABA

ANOVA

ATP

CC

CEC

CH2O

Chl

C02

DCM

E

EtOAc

FC

FOV

FWHM

gs

H20

H2SO4

HC1

HPLC

IAA

Photosynthesis rate

Abscisic acid

Analysis of variance

Adenosine triphosphate

Column chromatography

Cation exchange capacity

Carbohydrates

Chlorophyll

Carbon dioxide

Dichloromethane

Transpiration rate

Ethyl acetate

Field capacity

Field of view

Full width half maximum

Stomatal conductance rate

Water

sulfuric acid

Hydrochloric acid

High Performance Liquid Chromatography

Indole-3-acetic acid

xiv

K

LAI

MAP

MeOH

MPa

N

02

P

PAR

PE

PRI

Rf

RuBP

SIPI

spay

sot

swc

SWIR swP

TLC

TOC

Uv

VIS-NIIt

Potassium

Leaf area index

Months after planting

Methanol

Mega Pascal

Nitrogen

Oxygen

Phosphorus

Photosynthetic active radiation

Petroleum ether

Photochemical reflectance index

Retention factor

Ribulose-1,5-bophosphate

Structure independent pigment index

Soil-plant analysis development

Sulphur dioxide

Soil water content

Short wave infra-red

Soil water potential

Thin layer chromatography

Total organic carbon

Ultra violet\

Visible to near infra-red

xv

WO

Wl

W2 W3

WI

WUE

x

Rain fed treatment

Mild water stress treatment

Moderate water stress treatment

Extreme water stress treatment

Water index

Water use efficiency

Wavelength

xvi

CHAPTER 1

INTRODUCTION

1.1 Background

Jatropha curcas Linn, belongs to the family Euphorbiaceae, is an economically

viable alternative species to replace fast-depleting fossil fuels (Dehgan and Webster,

1979). The botanist Carl Von Linne first classified the plant in 1753 and gave a name that

is derived from the Greek word Jatros' means Doctor' and 'trophe' means Nutrition'. The

plant is a multipurpose shrub found throughout the tropics, known by 200 different

names, and is a native of South America, but also widely cultivated throughout Central

America, Africa and Asia (Dehgan and Webster, 1979). Oppenshaw (2000) stated that it

is still uncertain where the centre of origin is, but it is believed to be Mexico and South

America and has been introduced to Africa and Asia and is now cultivated world-wide.

This highly drought-resistant species is adapted to and and semi-arid conditions

(Oppenshaw, 2000). The current distribution shows that growth has been most successful

in the drier regions of the tropics with annual rainfall of 300-1000 mm. It occurs mainly

at lower altitudes (0-500 m) in areas with average annual temperatures well above 20 °C

but can grow at higher altitudes and tolerates slight frost. It grows on well-drained soils

with good aeration and it is claimed to be well adapted to marginal soils with low nutrient

content (Oppenshaw, 2000).

It is significant to point out that, the non-edible vegetable oil of J. curcas has the

requisite potential of providing a promising and commercially viable alternative to diesel

oil. It has desirable physicochemical and performance characteristics comparable to

1

diesel. Previous work by Foidl et al. (1996) and Eisa (1997) reported that the plant can

produce seeds with an oil content of 37%. They also mentioned that though there are

many positive claims on J. curcas high growth performance, it may emerged from

incorrect combinations of unrelated observations, often based on measurements of

singular and elderly J. curcas trees. Extrapolation of such measurements to larger areas

with J. curcas as a monoculture crop (or intercropping systems), ignores the growth

reduction in such systems occurring from the competition for natural resources, such as

radiation, water and nutrients (Ghosh et al., 2007). Nevertheless, the oil can be

combusted as fuel without being refined. It bums with clear smoke-free flame, tested

successfully as fuel for simple diesel engine (Oppenshaw, 2000). Cars could be run with

J. curcas without requiring much change in design. The demand of oils as an energy

source has been rapidly increasing and the mismatch between the demand and supply of

oil seeds has initiated various stakeholders in the form of farmers, agro based industries,

corporate sectors and, non-governmental organizations (NGO) to go for large scale

plantations with J. curcas as a commercial oil crop. The other uses of J. curcas other than

bio fuel source include soap production (Oppenshaw, 2000; Prakash et al., 2007), organic

fertilizer (Patolia et al., 2007), medicinal source (Sharma et al., 1997), and as bio-

chemical for pest control (Oppenshaw, 2000). This makes the plant a unique crop among

the various bio fuel plant sources (Zamora et al., 1997).

1.2 Biofuel production in Malaysia

Biofuels are a wide range of fuels which are in some way derived from biomass.

The term covers solid biomass, liquid fuels and various biogases (OPIEJ, 2010). Biofuels

are gaining increased public and scientific attention, driven by factors such as oil price

2

spikes, the need for increased energy security, and concern over greenhouse gas

emissions from fossil fuels (OPIEJ, 2010). In Malaysia, palm oil has been one of the

major sources for biofuel. However, it is impossible for palm oil to be used as biofuel

feedstock without incurring considerable losses due to astronomical crude palm oil prices

(Malaysian Business, 2008). The palms are showing definite signs of slowing down after

12 months of very strong growth from the previous period of October 2007 to September

2008. In February 2009, the Malaysian Palm Oil Board (MPOB) reported that total crude

palm oil (CPO) production declined by 10.7 per cent to 1.2 million tonnes (OPIEJ, 2010).

Some six million tonnes of palm oil for biodiesel was an apparent initial target, and

currently the country is not even producing half a million tonnes (OPIEJ, 2010). In

addition, the increase of global crude oil price had been a big burden for Malaysia

because the government has been subsidizing the fuel costs.

That gives the option for potential crop such as J. curcas to be used for biodiesel

production due to its main trait as a renewable and sustainable fuel. Sharma and Sarraf

(2007) emphasized that reliable scientific data on its agronomy is important for the

growth and development of its fruit and seeds to optimize mass biofuel production. To

ensure long-term productivity, agronomic conditions which include optimum soil texture,

water requirement, spacing, pruning and fertilization need to be assessed in both pilot and

large-scale plantations (Srivastava, 1999). Transesterification technology should be

commercially available, as equipment that can be easily adapted to Jatropha curcas

biofuel oil production (Foidl et al., 1996). Partnership with the oil industry may be

needed to formulate and evaluate the required fuel standards, provide for storage and set

up distribution facilities. Jatropha production could offer a new commercial activity for

3

mineral oil firms that wish to diversify their portfolio to include biofuel processing and

distribution, and blending fossil fuels with biofuel (Foidl et al., 1996). Nevertheless, the

situation in Malaysia is different where as palm oil is still a major market force, and it is

not economically feasible to put a similar emphasis on J. curcas. In consideration, it can

still be a bonus plant but not an alternative to oil palm, which gives better yield

(Malaysian Business, 2008).

1.3 Responses and adaptations to drought

Jatropha curcas requires carbon dioxide (CO2) from the air and water (H2O) from

the soil for converting solar radiation in the photosynthesis process into functional

carbohydrates (CH2O). To survive drought stress, a plant must either extract more water

from the soil, or effectively control the amount of water losses through transpiration. The

efficiency of soil water uptake by the root systems as well as control of stomatal aperture,

are key factors in determining the rate of transpiration (Jones and Mansfield, 1970; Hale

and Orcutt, 1987). Drought has profound effects on growth, yield, and plant quality (Hale

and Orcutt, 1987). The rate of cell expansion and ultimate cell size may well be inhibited

by the loss of turgor. Loss of turgor is probably the process most sensitive to water stress.

Fruits and grains may not enlarge because rapidly transpiring leaves create lowered water

potentials in the xylem, which may result in water actually leaving the fruits. Similar

result also reported by Arndt et al. (2001) where under water stress, biomass production,

such as shoot height, total biomass, total number of leaves, total leaf area, were

significantly decreased, while the physiological traits such as water use efficiency (WUE)

were significantly increased.

4

Pusat Khidmat Maklumat Akademluj. UNIVERSITI MALAYSIA SARAWA14

Water deficit can cause a decrease in photosynthesis rate either by a direct effect

on photosynthesis capacity of the mesophyll or by carbon dioxide limitation resulting

from stomatal closure (Tezara et al., 1999; and Lawlor, 2002). In many plant species,

stomatal closure has been suggested as the main regulatory mechanism of photosynthesis

under water stress (Farquhar and Sharkey, 1982). It is also important to note the role

played by the plant hormone abscisic acid (ABA) which reduce stomata opening and

vegetative growth in a response appropriate to the reduction in available water (Liang et

al., 1997). Studies have shown that leaves which grow in drier environment and higher

light intensity tend to have smaller and numerous stomata than those grown in wet and

shady conditions (Bunce, 1996; Bianco et al., 2005). In addition, spectral reflectance and

chlorophyll fluorescence can be used to quantify plant stress in relation to leaf

chlorophyll concentration. A reduction in leaf water content typically causes an increase

in reflectance wavelengths from 500 to 600 nm (Carter, 1994) attributed to the

desiccation in leaf structure at the cellular level (Carter, 1994; Aldakheel and Danson,

1997). It seems clear that plants perceive and respond to drought by quickly altering

various adaptation mechanisms in parallel with physiological and biochemical processes.

1.4 Preliminary study on J. curcas in Sarawak

Although J. curcas grows in semi-arid and and tropical areas and can be

considered as a drought tolerant species, several studies have shown that irrigated

conditions and intensive cultivation can also give the best fruits and hence seed

productions compared to dry rain-fed conditions (Rajagopal, 2007). Currently there is no

knowledge on the type of water regimes which best promotes the survival, growth and

yield performances of J. curcas. Sarawak particularly seems to be receiving rainfall all

5

year round with a certain short period of drought. The introduction of J. curcas trees,

especially in large numbers, in hedges or in plantations to high rainfall events has not

been studied so far and thus the need for the research to compare various water

conditions which can give the higher yield as a step towards promoting Jatropha planting

in Sarawak or other parts of Malaysia. In any case, it will be insightful to study the

morphological and physiological performances of a drought tolerant plant such as J.

curcas when exposed to higher water availability in order to compare its growth

performances with that of the plants habitual in and and semi-arid areas.

1.5 Problem statement

Most research on production of J. curcas thus far focus mainly on its suitability to

dry and and lands; whereas less attention has been paid to their adaptations to high water

availability. Kota Samarahan, Sarawak is an example of environment with high water

availability where it receives substantial rainfall and sunshine all year round. It was

suggested that although J. curcas is drought tolerant, it also performs better under non-

water stressed condition in which Malaysia may have an edge. However, the

documentation on plant responses and adaptation to varied levels (high and low) of water

regimes in terms of growth, morphological, and physiological traits was still lacking,

which needs immediate attention if cultivation of J. curcas was to be undertaken

seriously in areas of high water availability such as Malaysia.

6