The influence of soil water deficit imposed during various developmental
phases on physiological processes of tef (Eragrostis tef)
Dejene K. Mengistu
*
Mekelle University, College of Dryland Agriculture and Natural Resources, Department of Dryland Crop and Horticultural Sciences, P.O. Box 231, Mekelle, Ethiopia
1. Introduction
1.1. Background and rationale
Reduction of crop productivity results from complex interac-
tions among the environment, crop genetics, management, and
biotic stresses that could occur across a field. Stress has been
defined as ‘‘any environmental factor capable of inducing a
potentially injurious strain in plants’’ (IRRI, 2007). Of these, water
stress is one of the major causes of temporal and spatial crop yield
variability in the world. On a global basis, drought (agricultural
and/or meteorological water deficits) in conjunction with high
temperature and radiation, poses the most important environ-
mental constraint to plant survival and productivity (Boyer, 1982;
Hatch, 1992). Arid and semiarid regions of the world, such as
Ethiopia, suffer much from this crop production constraint because
of the inadequacy, irregularity or intensity of their natural rainfall
patterns.
Frequently recurrent droughts supplemented with lack of
efficient use of existing water resources have amplified the impact
of drought on the livelihood of Ethiopian farmers. Tef, which
constitutes about 22% (1.68 million tonnes) of the gross grain
production and 31% (2.11 million ha) of the total acreage of all the
seven major cereals grown in Ethiopia (CSA, 2000), has been grown
as a rescue crop in case of failure of other cereals (Ketema, 1997)in
some parts of the country where the recurrence of long period
drought is very common. Despite of this fact, the restriction of tef
growth as a food crop to Ethiopia, where it originated and
diversified (Assefa et al., 2003), has limited research on its
agronomic and physiological responses to water and other physical
stresses. The low national gain from this crop compared to other
cereals could be associated with limited knowledge of its water
relationships and lack of appropriate management at different
developmental stages.
Apart from an attempt made to examine the effect of water
stress at various development stages on the yield and yield
components of tef that focused on agronomic traits (Tefera et al.,
Agriculture, Ecosystems and Environment 132 (2009) 283–289
ARTICLE INFO
Article history:
Received 16 November 2008
Received in revised form 17 April 2009
Accepted 21 April 2009
Available online 17 May 2009
Keywords:
Tef (Eragrostis tef)
Water stress
Phenological phases
PAR
Physiological process
ABSTRACT
Physiological responses of tef (Eragrostis tef (Zucc.)) to water stress during establishment, vegetative, flag
leaf-1 and grain filling developmental stages were studied under glasshouse conditions in 2007 at
Henfaes Research Centre, University of Wales, Bangor, UK using a ‘‘near-factorial’’ randomised complete
block design. During each phenological phase plants were subjected to three levels of soil moisture
tension viz., FC (À0.12 MPa), 50%FC (À1.06 MPa) and 25%FC (À1.51 MPa) until the completion of the
specific phases and during the preceding and subsequent growth periods the stressed plants were
irrigated to field capacity (FC).
A maximum net CO
2
assimilation (12.15
m
mol m
À2
s
À1
) and transpiration (3.88 mmol m
À2
s
À1
) rates
were recorded in the control treatment. Both levels of water stress during flag leaf-1 and grain filling
development stages reduced these rates significantly. Severe water stress imposed during grain filling
stage produced the lowest rates in both CO
2
assimilation (À2.80
m
mol m
À2
s
À1
) and transpiration
(0.15 mmol m
À2
s
À1
). Response curves of CO
2
assimilation rates to PAR levels showed that initial
photosynthetic efficiency (at light saturation point) of severely stressed tef was less (0.013
m
mol CO
2
/
m
mol photons) than the corresponding efficiencies of other treatments (P < 0.001). The grain filling
stage of tef was the most sensitive to water stress and severe water stress caused significant reduction in
physiological performance of tef. The low yielding nature of tef could be associated with its low light use
efficiency which perhaps related to its leaf size and orientation. Therefore, improving tef light use
efficiency should be a national agenda to improve its yielding potential.
ß 2009 Elsevier B.V. All rights reserved.
* Tel.: +251 911082433; fax: +251 344409304.
E-mail address: dejenekmh@yahoo.com.
Contents lists available at ScienceDirect
Agriculture, Ecosystems and Environment
journal homepage: www.elsevier.com/locate/agee
0167-8809/$ – see front matter ß 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.agee.2009.04.013