Objectives Water logging damage during wheat seedling stage is a common disaster limiting the growth and yield of wheat under wheat-rice rotation system in Sichuan Plain. We studied the effect of foliar application of plant stimulants and fertilizers on the water logging resistance of wheat seedlings from the points of physiological responses and population growth, to provide an approach for alleviating the damage caused by water logging in wheat fields.

Methods A field experiment was carried out in Dayi County, Sichuan Province during wheat season after rice, the wheat cultivars included a multi-spike type ‘Shumai 1963’ and a large-spike type ‘Shumai 133’. Within 30 days after sowing of wheat, the relative soil moisture content was above 90%, leading to water lodging damage seriously on wheat seedlings. Six foliar treatments were setup at the three-leaf stage of wheat seedlings, included spraying S-Abscisic acid (S-ABA), poleiotropic azole·meata (PM), amino acid water soluble fertilizer (AF), humic acid water soluble fertilizer (HF), and combined spraying S-ABA and PM with AF (S+P+A), or with HF (S+P+H), and spraying tap water (CK) as a control. The seedling traits, leaf area index, development dynamics of tillerings and stems, grain-setting characteristics, and yield of wheat population were investigated. At jointing stage, leaf and tillering node samples were collected for determination of the malondialdehyde (MDA) content, antioxidant enzyme activities, and the accumulation of carbon and nitrogen assimilation.

Results Among the six treatments, S+P+H showed the highest anti-water logging effect and stable production effects on the multi spike type of Shumai 1963, and it can also produce similar effects on the large spike type of Shumai 133. Specifically, both spike types of wheat significantly improve the pre jointing population growth rate and leaf net assimilation rate, increase leaf area index and chlorophyll content; The sucrose content in leaves and tillering nodes increased by 38.8% to 70.3% compared to CK, the free amino acid content increased by 16.7% to 24.2%, and the proline content in leaves increased by 48.0% to 71.5%, respectively. MDA content in leaves and tiller nodes decreased by 28.0% to 51.2% compared to CK, while the activities of antioxidant enzymes superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX) in leaves increased by more than 41.3%, 47.6%, 89.9%, and 38.7% compared to CK, improving carbon and nitrogen metabolism and antioxidant capacity. The tillering ability of Shumai 1963 and Shumai 133 spikes increased by 28.2% and 58.3% compared to the control group, and the effective tillering rate significantly increased. The number of grains per spike, tiller spike weight, and grain number per spike on the main stem significantly increased, and the contribution rate of tiller yield increased by 6.1% and 8.8%, respectively. The final yield increased by 26.3% and 13.2%, respectively. Spraying HF alone also contributed to leaf growth and photosynthesis during the seedling stage, with a 12.2%, 5.6% increase in tiller yield contribution for Shumai 1963 and Shumai 133, and an actual yield increase of 15.4% and 16.5%, respectively. Spraying S-ABA on multi spike Shumai 1963 increased yield by 13.3%, while spraying AF on large spike Shumai 133 increased yield by 10%.

Conclusions Spraying one or a combination of several plant growth regulators and foliar fertilizers at the three-leaf stage can mitigate the adverse effects of water logging on wheat seedling growth through different pathways and to varying degrees. Physiologically, this practice promotes wheat leaf growth and chlorophyll content, enhances the accumulation of sugar and nitrogen metabolites in leaves and tillering nodes, boosts antioxidant enzyme activity to reduce membrane damage, protects tillering occurrence, and enhances the plasticity of the first tiller. From an agronomic perspective, applying plant growth regulators and foliar fertilizers can increase the population of stems and tillers, accelerate the growth rate of the population, improve the quality of spike formation, and ultimately boost yield. After applying the combined treatment, Shumai 1963 (a multi-spike variety) exhibited higher levels of sugar metabolites in leaves and tillering nodes, as well as higher SOD and APX activities in leaves, compared to Shumai 133 (a large-spike variety). Additionally, Shumai 1963 had lower nitrogen metabolite content and MDA content, and produced more tillers that formed spikes. Overall, the effect of spraying humic acid-based foliar fertilizer is greater than that of amino acid-based foliar fertilizer. The combined effect of S-abscisic acid (S-ABA), paclobutrazol·piperidine, and humic acid-based foliar fertilizer is also more pronounced than their combination with amino acid-based foliar fertilizer.