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Biostimulants offer a novel approach for the regulation of crucial physiological processes in plants. Recently, it has been observed that the application of biostimulants on both seeds and plants may ameliorate to some extent the negative effects of abiotic stresses such as drought, heat, salinity, and others. In the climate conditions of Bulgaria, the early developmental stages of warm climate crops, like maize, often occur under suboptimal temperatures. Although the mitigation of abiotic stress is perhaps the most frequently cited benefit of biostimulant formulations, little is known about their influence on chilling-stressed plants. The aim of our study was to evaluate the effects of a biostimulant from the group of protein hydrolysates on both the growth and the photosynthetic performance of chilling-exposed young maize plants grown in controlled environment. Here, we report that application of a protein hydrolysate increased the performance of chilled maize plants, as demonstrated by leaf gas exchange, photosynthetic pigment content, and chlorophyll fluorescence, but did not affect their growth. Nevertheless, based on the better preserved photosynthetic performance of the biostimulant-treated maize plants exposed to chilling, we assume that under subsequent favorable conditions their growth would recover more quickly as compared to the untreated ones. [ABSTRACT FROM AUTHOR]

Nowadays the biologically active substances are very attractive, because they are harmless and ecological friendly. Their application is not only economically profitable, but also improves the action of the fertilizers and increases the yields. The study aims to investigate the effect of some foliar fertilizers and biostimulators on the elements of productivity, seed yield and the essential oil content and composition of Lozen 1 coriander (Coriandrum sativum L.) cultivar. The field trial was carried out on leached Smolnitsa soil type in the region of the village of Zhrebino, South-Eastern Bulgaria in the period 2018–2020. The experiment was arranged according to the randomized complete block design in four replications with a plot size of 15 m2, after predecessor wheat. The treatment of coriander with the leaf fertilizer Masterblend in a dose of 2.5 kg ha-1 resulted in an average yield increase of 11.8% compared with the untreated control. After treatment with the foliar applied products an increase in the essential oil content from 2.9% to 9.6% was established, as the highest values were obtained when using the biostimulator Fertigrain – 1.26% and the foliar fertilizer Masterblend – 1.25%. The most frequent components of the essential oil were linalool, γ-terpinene, α-pinene and camphor. The highest values of linalool were observed after the application of the products Masterblend and Poly Plant. The used products stimulated the biological potential of the tested cultivar and could be recommended for further investigations by other essential oil crops. • Coriander is one of the major essential oil crops grown in Bulgaria. • Application of foliar fertilizers and biostimulators increased the essential oil content. • Linalool content was affected by the foliar treatment with Masterblend in a dose of 2.5 kg ha-1 and Poly Plant in a dose of 1 kg ha-1. [ABSTRACT FROM AUTHOR]