Ecologia Mediterranea

One chamber was left at the greenhouse CO 2
conditions (referred to as ambient treatment –
ACO 2 ) where the CO 2 concentration was
around 500 ppm (Figure 1), and the other
chamber was kept at high concentration of
CO 2 (referred to as enriched treatment –
ECO 2 ). CO 2 concentration was kept at around
1000 ppm (Figure 1). The source of CO 2 was
20-kg CO 2 canisters. The CO 2 levels were
monitored using a carbon dioxide monitor and
controller (TONGDY Ltd.). All other conditions
were kept similar in both chambers (Figure
1). Three groups of C. ciliaris plants, were
grown in plastic pots (30 cm in diameter),
exposed to enriched, ambient, or alternating
CO 2 . The salinity stress sub-group contained
four pots each with 20 planted seeds of C. ciliaris.
Seeds were planted on 11 February. All
plants were grown within pots from locally
collected seeds.
ecologia mediterranea – Vol. 38 (2) – 2012
Salinity stress affects growth responses of Cenchrus ciliaris under CO 2 enrichment
Figure 1 – Daily variations in A) Temperature, B) Humidity, C) light, and D) CO 2 concentration
in the two growing chambers over the trial period.
Plants that were grown under enriched CO2 conditions were exposed continually to
enriched atmospheric CO2 during the whole
trial between 7:00 to 18:00. A third group was
referred to as alternating treatment (ALCO2 )
where plants were grown under changing
exposure between ambient and enriched
atmospheric CO2 , every two weeks. Plant
under salinity treatment were supplied with
saline water (salinity=2.15 ppt), while the
other plants in the other two treatments were
irrigated with tap water (salinity=0.75 ppt).
Shoot length, number of blades (green/dry),
blade area and inflorescence production were
measured every week throughout the trial
period. The number of stomata was counted
per square area using the epidermal peeling
method. The peeling was done two to three
times for each of three replicates.
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