Drought-protective effects of nutrient seed treatments during early growth of oilseed rape

Abstract

Crop production is increasingly affected by water limitation even in temperate climates due to a rising frequency of drought periods, related with global change. The stress-protective nutrients, discussed as a mitigation strategy, were investigated for their potential drought-protective effects of nutrient seed treatments, based on Ca, K, Fe, Zn, Mn on early growth of oilseed rape (OSR). Responses were observed in five OSR hybrids under greenhouse conditions on two soils with contrasting properties (sandy-loam pH 5.6 vs. silty-loam pH 6.9) in two independent pot experiments. A 7-days drought period with reduced soil moisture level (40% soil water-holding capacity. WHC) inhibited shoot and root growth and caused irreversible wilting and leaf necrosis (27-46% of total leaf area) particularly on the sandy-loam with lower WHC, depending on the investigated genotype. Nutrient seed treatment increased shoot (10-15%) and particularly root growth (14-23%) as well as nutrient accumulation, but also reduced the proportion of irreversibly damaged leaves to 17-21%, with the largest effect in strongly drought-affected genotypes under the challenging conditions on the sandy-loam soil. Analysis of physiological stress indicators revealed increased accumulation of phenolics (23-28%), antioxidants (14-47%) and higher activities of ascorbate peroxidase (APX) (23-87%) in the leaf tissue, counteracting drought-induced oxidative stress. Moreover, APX activity was positively related with root length (R20.8953), suggesting a protective effect on drought-induced oxidative IAA degradation with inhibitory effects on root growth. Increased levels of absisic, jasmonic and salicylic acids during drought stress recovery point to stress priming effects, strengthening the natural adaptive responses to water limitation.