Clipping Effects on the Growth Variation, Water Use Efficiency and Photosynthetic Activity in Buffel Grass (Cenchrus ciliaris L.) Poaceae
M. Zaman Allah,
Buffel grass (Cenchrus ciliaris)
growth, biomass allocation to root and shoot, water use efficiency and
photosynthetic activity were measured in response to two defoliation heights
(5 and 3 cm). Results showed that plants clipped at 5 cm showed a significant
increase of diameter and water use efficiency as well as higher leaf water
potential with a subsequent increase of stomatal conductance and photosynthetic
activity. On the other hand, plants clipped at 3 cm presented an increase
in photosynthetic activity parameters but a significant decrease in all
growth parameters and water use efficiency.
Bufflel grass (Cenchrus ciliaris syn Pennisetum
ciliare) is a C4 bunch grass native to dry areas of the
African continent, West Asia and India and has been widely introduced
in arid and semi-arid regions of the world (MSeddi et al., 2002).
The most drought tolerant of the commonly sown grasses, occurs naturally
in areas with average annual rainfall from as low as 100 mm. The species
has a larger and deeper root system capable of providing effective soil
erosion control in arid and semi-arid regions (Harwood et al.,
1999; Gyasi-Agyei et al., 2005). C. ciliaris is typically
propagated by seeds that can remain dormant for a considerable period
of time before reaching maturity (Burquez-Montijo et al., 2002).
In Tunisia, the species is scarce and growth is stunted, because it is
selectively overgrazed (Chaieb et al., 1996). Studies on C.
ciliaris have concentrated on estimating the nutritional value and
preference by animals through intake, diets, crude protein and in vitro
organic matter digestibility analysis (Ramirez et al., 1997; Mero
and Udén, 1998; Ronquillo et al., 1998; Foroughbackhch et
al., 2001). Other studies focused on nitrogen use efficiency (Rudmanna
et al., 2001) and on the variation and the relationships of several
seed and spike-related traits of C. ciliaris (M`Seddi et al.,
The effects of defoliation on plant growth are complex
(Painter and Belsky, 1993): sometimes inhibitory, nil or stimulatory (Oesterheld
and McNaughton, 1988, 1991; Georgiadis et al., 1989; Schmid et
al., 1990). Understanding the impacts of defoliation height on the
performance of grasses is therefore important in the management of grazing
areas since animals grazed the plants at different heights (Floret and
Pontanier, 1982; Laca et al., 1992). It is especially important
in arid and semi-arid environments where, apart from water scarcity, the
levels at which grasses are grazed have a major influence on their persistence
in the environment.
This study was undertaken to estimate the effect of defoliation
height (3 and 5 cm above ground level) on the performance of buffel grass
in growth, biomass allocation to shoot and root, water use efficiency
and photosynthetic activity.
MATERIALS AND METHODS
This study was carried out at the Institut des Régions
Arides de Médenine. The seeds of C. ciliaris were collected
during spring 2003 in the protected national park of Bouhedma in southern
Tunisia and sown in cylindrical plastic pots (top diameter: 20 cm, height:
18 cm, down diameter: 17 cm) with three drainage holes and containing
4 kg of collected soil: conductivity 5.6 mS cm-1, pH 7.5, total
limestone 8%, active limestone 2.5%, gypsum 0.4% and organic mater 0.7%.
The seeds were sown to obtain three plants per pot under glasshouse conditions
with day/night temperatures of 25/30 °C throughout the experimentation
(180 days after sowing). Before sowing, the pots were brought to field
capacity. Fifteen Days After Sowing (DAS) and during 6 months, water was
supplied at the rate of 20 mm each 15 days corresponding to a total amount
of water of 240 mm to ensure adequate soil moisture.
Defoliation treatments: All the plants were submitted
to three defoliation treatments: control (C) not cut, C3 (cut at 3 cm
above soil surface in the pot) and C5 (cut at 5 cm above soil surface
in the pot). The cuts were realized with scissors four times. The first
three cuts were realized at 63, 84 and 105 DAS, the last cut occurred
at 180 DAS.
Plant growth, Water Use Efficiency (WUE) and photosynthetic
activity measurements: Before each cut, plant height and diameter
were measured. After each cut, shoots were placed in an oven for 24 h
at 105 °C and their dry weight was measured. At the end of the experiment
(180 DAS) roots were separated from shoots and both shoots and roots dry
weights of all the plants were measured. Water use efficiency was calculated
Photosynthetic activity was measured from 63 to 105 DAS.
Before defoliation, leaf water potential (ψ), stomatal conductance,
transpiration rate and photosynthesis rate were measured on six randomly
chosen leaves of each clipping treatment using LCi Portable Photosynthesis
System (ADC BioScientific CO., UK).
Statistical analysis: Data were analyzed by one-way
analysis of variance procedure (ANOVA) using SAS (9.0 for Windows). Subsequent
comparison of means was performed using the Duncan`s multiple range test
RESULTS AND DISCUSSION
Plant growth and water use efficiency: Defoliation
affected C. ciliaris biomass production depending on the cutting
height. As compared to the control plants, those defoliated at 5 cm were
not affected in shoot biomass but showed a significant decrease of 24.74%
in root biomass (Table 1). This indicated that when
plants were defoliated to 5 cm, resources were allocated to the shoot
over roots for shoot compensation. The ability of 5 cm defoliated plants
to compensate shoot biomass resulting in an equal shoot dry mass with
the control seemed not to be associated with recovering in plant height
but with an increase in plant diameter (Table 1). The
increased plant diameter may result from tillering stimulated by the removal
of apical dominance after defoliation (Manske, 1994, 2003; Briske and
Richards, 1995) but most of the additional tillers remained vegetative
and the effect of defoliation on vegetative biomass was generally not
significant (Gutman et al., 2001). Compensatory growth following
defoliation has long been known in plants but may depend on species, water
and nutrients availability as well as severity of grazing (McNaughton,
1984; Gutman et al., 2001). However, 5 cm defoliated plants were
not able to completely recover the total biomass and showed a decrease
in the root to shoot ratio.
Plants defoliated at 3 cm showed a decrease in all plant
growth parameters in a higher way than did defoliation at 5 cm. As compared
to the control, defoliation at 3 cm height decreased total biomass by
51%, shoot biomass by 34% and root biomass by 78%, suggesting that roots
were more sensitive than shoot when plants were clipped to 3 cm. Sensitivity
of root over shoot following defoliation was also observed at 5 cm cut.
Thus, defoliation most likely affects more the roots than shoot in buffel
grass whatever the clipping height.
Many Pot and field studies have reported a superficial
root system development and a reduction of root biomass as well as a decrease
of root length after defoliation (McNaughton et al., 1983; Mawdsley
and Bardgett, 1997; Manske, 1999, 2000). Chaieb et al. (1996) reported
a decrease in root and shoot biomass as well as a reduction of root density,
distribution and rooting depth when buffel grass is cut at ground level
and under high and moderate cutting frequency.
This may explain the decrease of about 68% in root to
shoot ratio after 3 cm defoliation.
In addition, plants cut at 3 cm do not recover and were
not able to produce at their potential level; the
||Shoot (S), root (R) and total (T) plant dry weight (DW
g plant-1), Root to Shoot Ratio (RSR) and Water Use Efficiency
(WUE) of plants subjected or not to cutting at 5 cm (C5) and 3 cm
(C3) in Bufflel grass (C. ciliaris) grown under glasshouse
|In columns, means with the same letter(s) are not significantly
compensatory growth was therefore not observed. Present
results are in agreement with those obtained for various species (Stockdale,
1992; Virkajärvi, 2003). High defoliation (28% shoot mass or higher
than 25% leaf area removed) reduce the root to shoot ratio relative to
moderate or non-defoliated Heterotheca subaxillaris plants (Mihaliak
and Lincoln, 1989). Clipping to 4 cm reduced both the biomass of root
and leaf base of Lolium perenne and Poa trivialis compared
with those clipped to 8 cm (Thornton and Millard, 1996). For timothy (Phleum
pratense) and meadow fescue (Festuca pratensis) the effect
of three defoliation heights, 3, 6 and 9 cm increased the regrowth rates
by 27% and the cumulative regrowth dry matter yield increased by 29% of
both species by increasing the cutting height from 3- 9 cm (Virkajärvi,
2003). A four weeks defoliation interval of an irrigated Persian clover
(Trifolium resupinatum) was more productive when defoliated to
4 cm above ground level than ground level defoliation (Stockdale, 1992).
Water use efficiency expressed as the ratio of total
plant biomass to total water received increased with defoliating at 5
cm but decrease with 3 cm clipping level as compared to the control (Table
1). The low WUE at 3 cm defoliation can be attributed to the reduced
total biomass production.
Photosynthetic activity: Photosynthetic parameters
are presented in Fig. 1(A-D). As defoliation started
at 63 DAS, initial leaf water potential (ψ) values were -1.94 MPa
for all the plants (Fig. 1A). During all the experimentation,
from 63 to 105 DAS, ψ values vary from -1.94 to -2.61 Mpa for the
control, to -2.25 MPa for 3 cm defoliated plants and to -1.85 MPa for
plants cut to 5 cm. ψ significantly increased with defoliation height
at both 84 and 105 DAS. Similar results were obtained with various species
(Wolf and Parrish, 1982; Noitsakis and Berger, 1984; Lazaridou, 2001).
The low ψ values of the control can be attributed to faster maturation
(Link et al., 1990). In contrast, defoliation maintained the plants
at the vegetative stage and this effect was accompanied by an increase
in ψ. The water potential differences are probably in the same order
as the relative water content (Kappen et al., 1994). High ψ
values in defoliated plants induced significantly higher values of stomatal
conductance (Fig. 1B) and consequently higher transpiration
rates at both 84 and 105 DAS (Fig. 1C). The ability
of the defoliated plants to maintain an important stomatal conductance
is accompanied by a higher photosynthesis rate (Fig. 1D)
indicating a higher CO2 uptake. New leaves emerging after defoliation
have been found to have greater efficiency for CO2 assimilation
||Effects of defoliation height on leaf water potential
(A), stomatal conductance (B), transpiration rate (C) and Photosynthesis
rate (D). At each corresponding DAS, means indicated by the same letter(s)
are not significantly different at 5%
(Khan and Lone, 2005). Despite the reduction of photosynthetic
surfaces by defoliation, clipped plants showed higher photosynthetic capacity.
The increase in the photosynthetic parameters of plants defoliated at
84 DAS and 105 DAS was probably due to higher photosynthates requirement
of leaves following defoliation for growth and development.
Grazing-tolerant species often respond to defoliation
by increasing photosynthetic rates, allocating resources to photosynthetic
tissue over roots (Caldwell et al., 1981; McNaughton, 1984; Coughenour
et al., 1985). On the other hand the clipping interval and the
decrease in root biomass which in turn reduce soil water extraction capacity
of 3 cm defoliation plant may explain to reduction to produce at their
potential level and therefore can not recover. These results are relevant
in the restoration of degraded pasture land based on species sowing methods
in arid region.
Briske, D.D. and J.H. Richards, 1995.
Plant Responses to Defoliation: A Physiological, Morphological and Demographic Evaluation. In: Wildland Plants: Physiological Ecology and Developmental Morphology, Bedunah, D.J. and R.E. Sosebee (Eds.). Soc. Range Manage, Denver, Co., pp: 635-710
Burquez-Montijo, A., M. Miller and A. Martinez-Yrizar, 2002.
Mexican Grasslands, Thornshrub and the Transformation of the Sonoran Desert by Invasive Exotic Buffelgrass (Pennisetum ciliare
). In: Invasive Exotic Species in the Sonoran Region, Tellman, B. (Ed.). University of Arizona Press, Tucson, pp: 126-146
Caldwell, M., M. Richards, J.H.D.A. Johnson, R.S. Nowak and R.S. Dzuree, 1981.
Coping with herbivory: Photosynthetic capacity and resource allocation in 2 semiarid Agropyron bunch grasses. Oecologia, 50: 14-24.CrossRef |
Chaieb, M., B. Henchi and M. Boukhris, 1996.
Impact of clipping on root systems of 3 grasses species in Tunisia. J. Range Manage., 49: 336-339.Direct Link |
Coughenour, M.B., S.J. McNaughton and L.L. Wallace, 1985.
Responses of African tall-grass (Hyparrhenia filipendula
) to defoliation and limitations of water and nitrogen. Oecologia, 68: 80-86.CrossRef |
Floret, C. and R. Pontanier, 1982.
Aridity in Presaharian Tunisia. Paris: ORSTOM.
Foroughbackch, R., R.G. Ramirez, L. Hauad, J. Alba-Avila, C.G. Garcia-Castillo and M. Espinosa-Vazquez, 2001.
Dry matter, crude protein and cell wall digestion of total plant, leaves and stems in llano buffelgrass (Cenchrus ciliaris
). J. Applied Anim. Res., 20: 181-188.CrossRef | Direct Link |
Georgiadis, N.J., R.W. Ruess, S.J. McNaughton and D. Western, 1989.
Ecological conditions that determine when grazing stimulates grass production. Oecologia, 81: 316-322.CrossRef |
Gutman, M., I. Noy-Meir, D. Pluda, N.A. Seligman, S. Rothman and M. Sternberg, 2001.
Biomass partitioning following defoliation of annual and perennial Mediterranean grasses. Conserv. Ecol., 5: 1-1.Direct Link |
Gyasi-Agyei, Y., S.P. Bhattarai, J. Fox and D. Nissen, 2005.
Simultaneous multisite railway embankment slopes (batters) erosion control for a new spur line. Proceedings of the 8th International Railway Engineering Conference, 29-30 June 2005, London, UK.
Harwood, M.R., J.B. Hacker and J.J. Mott, 1999.
Field evaluation of seven grasses for use in the revegetation of lands disturbed by coal mining in central Queensland. Aust. J. Exp. Agric., 39: 307-316.Direct Link |
Kappen, L., G. Schultz and R. Vanselow, 1994.
Direct observations of stomatal movements. Ecol. Stud., 100: 231-246.Direct Link |
Khan, N.A. and P.M. Lone, 2005.
Effects of early and late season defoliation on photosynthesis, growth and yield of mustard (Brassica juncea
L.). Brazilian J. Plant Physiol., 17: 181-186.CrossRef | Direct Link |
Laca, E.A., E.D. Ungar, N.G. Seligman and M.W. Demment, 1992.
Effects of sward height and bulk density on bite dimensions of cattle grazing homogeneous swards. Grass Forage Sci., 47: 91-102.CrossRef |
Lazaridou, M., 2001.
Effect of cutting intensity on productivity and on water relations of the leaf tissue of herbage forage species. Ph.D Thesis, Aristotle University of Thessaloniki, Thessaloniki, Greece, pp: 261.
Link, S.O., G.W. Gee and J.L. Downs, 1990.
The effect of water stress on phenological and ecophysiological characteristics of cheatgrass and Sandberg's bluegrass. J. R. Manage., 43: 506-513.Direct Link |
Manske, L.L., 1994.
Grazing management for Northern Great Plains rangelands. NDSU Dickinson Research Extension Center. Range Research Report DREC 94-1004. Dickinson, ND., pp: 11.
Manske, L.L., 1999.
Can native prairie be sustained under livestock grazing? Proceedings of the 5th Prairie Conservation and Endangered Species Conference, Provincial Museum of Alberta, (PCE'99), Natural History Occasional Paper No. 24. Edmonton, Alberta, pp: 99-108
Manske, L.L., 2000.
Management of prairie in the Northern Great Plains based on biological requirements of the plants. NDSU Dickinson Research Extension Center. Range Science Report DREC 00-1028. Dickinson, ND., pp: 12.
Manske, L.L., 2003.
Effects of grazing management treatments on rangeland vegetation. NDSU Dickinson Research Extension Center. Range Research Report DREC 03-3027. Dickinson, ND., pp: 6.
Mawdsley, J.L. and R.D. Bardgett, 1997.
Continuous defoliation of perennial ryegrass (Lolium perenne
) and white clover (Trifolium repens
) and associated changes in the composition and activity of the microbial population of an upland grassland soil. Biol. Fertil. Soils, 24: 52-58.CrossRef | Direct Link |
McNaughton, S.J., L.L. Wallace and M.B. Coughenour, 1983.
Plant adaptation in an ecosystem context: Effects of defoliation, nitrogen and water on growth of an African C4 sedge. Ecology, 64: 307-318.CrossRef | Direct Link |
McNaughton, S.J., 1984.
Grazing lawns: Animals in herds, plant form and coevolution. Am. Nat., 124: 863-886.CrossRef | Direct Link |
Mero, R.N. and P. Uden, 1998.
Promising tropical grasses and legumes as feed resources in Central Tanzania V. Effect of supplementing Cenchrus ciliaris
hay with leaves from four legumes on intake and digestibility by growing Mpwapwa bulls. Anim. Feed Sci. Technol., 70: 111-122.Direct Link |
Mihaliak, C.A. and D.E. Lincoln, 1989.
Plant biomass partitioning and chemical defense: Response to defoliation and nitrate limitation. Oecologia, 80: 122-126.CrossRef |
M'Seddi, K., M. Visser, M. Neffati, D. Reheul and M. Chaieb, 2002.
Seed and spike traits from remnant populations of Cenchrus ciliaris
L. in South Tunisia: High distinctiveness, no ecotypes. J. Arid Environ., 50: 309-3254.CrossRef |
Noitsakis, B. and A. Berger, 1984.
Relations hydriques chez Dactylis glomerata
et Dichanthium ischaeum
cultivés sous deux régimes hydriques contrastes. Acta Oecol. Plant, 5: 75-88.Direct Link |
Oesterheld, M. and S.J. McNaughton, 1988.
Intraspecific variation in the response of Themeda triandra
to defoliation: The effect of time of recovery and growth rates on compensatory growth. Oecologia, 77: 181-186.CrossRef |
Oesterheld, M. and S.J. McNaughton, 1991.
Effect of stress and time for recovery on the amount of compensatory growth after grazing. Oecologia, 85: 305-313.CrossRef |
Painter, E.L. and A.J. Belsky, 1993.
Application of herbivore optimization theory to rangelands of the western United States. Ecol. Applied, 3: 2-9.Direct Link |
Ramirez, R.G., J.B. Quintanilla and J. Aranda, 1997.
White-tailed deer food habits in Northeastern Mexico. Small Ruminant Res., 25: 141-146.CrossRef |
Ronquillo, M.G., M. Fondevila, A.B. Urdaneta and Y. Newman, 1998. In vitro
gas production from buffel grass (Cenchrus ciliaris
L.) fermentation in relation to the cutting interval, the level of nitrogen fertilisation and the season of growth. Anim. Feed Sci. Technol., 72: 19-32.CrossRef | Direct Link |
Rudmanna, S.G., P.J. Milhamb and J.P. Conroy, 2001.
Influence of High CO2
Partial Pressure on Nitrogen Use Efficiency of the C4 Grasses Panicum coloratum
and Cenchrus ciliaris
. Ann. Bot., 88: 571-577.CrossRef | Direct Link |
Schmid, B., S.L. Miao and F.A. Bazzaz, 1990.
Effects of simulated root herbivory and fertilizer application on growth and biomass allocation in the clonal perennial Solidago canadensis
. Oecologia, 84: 9-15.CrossRef |
Stockdale, C.R., 1992.
Effects of frequency and height of defoliation on the production of a Persian clover-annual ryegrass sward. Aust. J. Exp. Agric., 32: 339-344.CrossRef |
Thornton, B. and P. Millard, 1996.
Effects of severity of defoliation on root functioning in grasses. J. R. Manage., 49: 443-447.Direct Link |
Virkajärvi, P., 2003.
Effects of defoliation height on regrowth of timothy and meadow fescue in the generative and vegetative phases of growth. Agric. F. Sci., 12: 177-193.Direct Link |
Wolf, D.D. and D.J. Parrish, 1982.
Short-term growth responses of tall fescue to changes in soil water potential and to defoliation. Crop Sci., 22: 996-997.Direct Link |