Separate or combined effects of soil compaction and/or drought on gas exchange, chlorophyll fluorescence and physiological traits of maize (Zea mays L.) hybrids

Abstract

In the natural environment, plants are subjected to simultaneous or sequential presence of various abiotic and/or biotic stresses, including soil compaction and soil drought. The effects of these stresses tested separately are relatively well understood, but still little is known about their simultaneous effects on plants. Our research involved four single hybrids of maize differing in their degree of susceptibility to soil compaction and drought. We investigated the effects of low and high soil compaction under optimal irrigation (LI, HI) and under three-week long soil drought (LD, HD), on the gas exchange (Pn, E, gS, Ci) and chlorophyll fluorescence parameters (F0, Fm, Fv, Fv/Fm), total leaf area (LA), leaf greening (SPAD), leaf water deficit (WD), leaf water potential (ψ) and membrane injury (MI). The plants experiencing high soil compaction (HI) showed a decrease in all parameters of gas exchange (Pn, E, gS, Ci), leaf area (LA), leaf greening (SPAD) and the maximal quantum efficiency of PSII (Fv/Fm) in comparison with plants growing in non-compacted soil (LI). An increase was observed in the other fluorescence parameters, i.e., F0, Fm and Fv and leaf WD, ψ and MI in HI vs. LI variants. In the plants exposed to drought (LD, HD), the changes in the measured traits were greater, especially for the sensitive hybrids P-8400 and NS-3023, than for the plants from LI treatment. A significant interaction between the degree of stress susceptibility and relative trait change was observed for practically all of the measured features. Moreover, in the short recovery period after the end of drought, the measured traits in LD and HD plants did not fully return to the control level, especially in the case of the sensitive hybrids (P-8400 NS-3023). The physiological reaction of maize hybrids to soil compaction and/or soil drought indicated the genetically determined variability of tolerance to those stresses. Significant correlation between RTC and stress susceptibility indexes (S-SI) provided suitable criteria for the hybrid selection. Also, our results showed the plasticity and capability of maize hybrids to respond to environmental conditions.