Effects of rootzone CO2 and O2 levels on seed germination and stolon growth of Cynodon dactylon

Abstract

The role of rootzone CO2 and O2 levels on seed germination and plant growth is not fully defined. The aim of the present study was to investigate the effects of supraoptimal CO2 in combination with different O2 concentrations on seed germination and the growth of pre-rooted stolon segments of Cynodon dactylon. Seeds of “Princess 77” were germinated in specialized airtight tubes for 21 days. Gas mixtures containing 40–20, 40–10, 40–2.5% CO2–O2, or air were injected every 12 h. The establishment of bermudagrass stolons took place in micro-lysimeters for 28 days, while the rootzone was injected with either ambient air (control) in natural conditions or with the above-mentioned gas mixtures. For the determination of the effects of soil gases on stolon growth, the cumulative clippings dry weight, the root dry weight, the root total area and total length were recorded. The leaf chlorophyll, the relative water content, and the soluble sugars of both leaves and roots were also measured. The presence of 40–20, 40–10 and 40–2.5% CO2–O2 increased the final germination compared with the control. The gas mixtures as rootzone gases, affected the plant growth rate differently. The root growth was suppressed in all three gas treatments, but fructose and glucose root concentrations of the stolons treated with 40–2.5% CO2–O2 were significantly higher 28 days after the initiation of the gas treatments (DGT). Plants under the 40–20% CO2–O2 treatment showed initially a high sward growth. The Chlb concentration showed significant reduction under 40–10 and 40–2.5% CO2–O2, while the Chla/b of the leaves increased in the treatment with 40–2.5 CO2–O2 28 DGT.