Arbuscular Mycorrhizal Fungi Enhance Tolerance of Rosa multiflora cv. Burr to Bicarbonate in Irrigation Water

ABSTRACT

High bicarbonate (HCO₃ ⁻) of irrigation water can be detrimental to plant growth in sustainable horticultural production systems. The ability of arbuscular mycorrhizal fungi (AMF), ZAC-19, (composed of Glomus albidum, Glomus claroideum, and Glomus diaphanum) to enhance tolerance to HCO₃ ⁻ was tested on Rosa multiflora cv. Burr. Arbuscular mycorrhizal colonized and non-inoculated (non-AMF) plants were treated with 0, 2.5, 5, and 10 mM HCO₃ ⁻. Increasing HCO₃ ⁻ concentration and associated high pH and electrical conductivity (EC)—reduced plant growth, nutrient uptake, and acid phosphatase activity, while increasing alkaline phosphatase activity (ALP). Inoculation with AMF enhanced plant tolerance to HCO₃ ⁻, as indicated by greater growth (leaf, stem, and total plant dry weight, leaf area and leaf area ratio), leaf elemental concentration [nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), iron (Fe), zinc (Zn), aluminum (Al), boron (B)], leaf chlorophyll concentration, higher mycorrhizal inoculation effect, lower root Fe reductase activity, and generally lower soluble ALP activity. While AMF colonization was reduced by increasing HCO₃ ⁻ concentration, colonization still occurred at high HCO₃ ⁻ concentration. At 2.5 mM HCO₃ ⁻, AMF plant growth was comparable to plants at 0 mM HCO₃ ⁻, further indicating the beneficial effect of AMF for alleviation of HCO₃ ⁻ plant stress.

Keywords:

• alkalinity
• acid phosphatase (ACP)
• alkaline phosphatase (ALP)
• iron (Fe)
• iron reductase
• phosphorus (P)
• plant nutrition

ACKNOWLEDGMENTS

We gratefully appreciate the technical assistance of Dr. Chuanjiu He, Matt Kent, Paul Greer, and Donita Bryan. We thank Dr. D.W. Reed, Dr. H.B. Pemberton, and two anonymous reviewers for critical review of the manuscript.

Notes

^z Mycorrhizal inoculation effect [MIE (%) = (total DW of AMF plant-total DW of non-AMF plant)/(total DW of non-AMF plant)^{− 1} × 100].

^y Means ± SE, (n = 9).

^x Significance according to ANOVA, NS, ∗, ∗∗, ∗∗∗, nonsignificant and significant P ≤ 0.05, 0.01, 0.001, respectively.

^z Specific leaf area [leaf area (cm²)]/[leaf DW (g^{− 1})].

^y Leaf area ratio [leaf area (cm²)]/[plant DW (g^{− 1})].

^x Means ± SE (n = 9).

^w Significance according to ANOVA, NS, ∗, ∗∗, ∗∗∗, nonsignificant and significant P ≤ 0.05, 0.01, 0.001, respectively.

^z Means ± SE, (n = 3).

^z Means ± SE, (n = 3).

^z Means ± standard error (n = 3, 675 observations per treatment from 225 1-cm root segments).

^y Significance according to ANOVA, NS, ∗, ∗∗, ∗∗∗, nonsignificant and significant P ≤ 0.05, 0.01, 0.001, respectively.