Impact of environmental conditions, stress severity and dose application on caffeine-related improved lentil productivity

Abstract

Flowering and pod formation are two of the most sensitive pheno-phases in lentil ( Lens culinaris Medik.) development, and both can be strongly influenced by environmental conditions, biotic or abiotic stress. Caffeine (1,3,7-trimethylxanthine), a secondary metabolite within purine alkaloids, has a strong potential for its use as an active ingredient in biostimulant formulations. To evaluate the impact of environmental conditions, stress type, and dose on caffeine application effectiveness, we compared how various doses of caffeine influenced lentil production, pod formation, reproductive phenology, and foliar stress markers in irrigated plants, water-stressed plants, and plants exposed to the stem holoparasite field dodder ( Cuscuta campestris Yunck.) in a controlled greenhouse experiment. Three caffeine concentrations (10 −5 M, 10 −4 M, and 10 −3 M) were tested, which were applied twice (at initial flowering and pod formation), and compared to a control treatment (without caffeine). Results showed that the highest caffeine dose increased lentil production by nearly 50% in irrigated plants, but not in water-stressed plants or those exposed to the holoparasite. Both water deficit and parasitism had a very negative impact on lentil production, with a yield reduction of 66% and 87% respectively, effects that were not counterbalanced by caffeine application. Furthermore, foliar stress markers, such as F v / F m ratio and malondialdehyde content, showed a much stronger sensitivity of lentil plants to biotic than abiotic stress, and a higher impact of both stresses on flowering and fruit formation than on the vegetative physiological status. We conclude that (i) both abiotic and biotic factors strongly negatively influence the physiology of lentil plants, in particular pod and lentil production; and (ii) environmental conditions and both abiotic and biotic stresses have a strong impact on the potential response of plants to caffeine when used as a potential ingredient for biostimulant formulations. • Caffeine treatment at the highest studied dose (10 −3 M) improved fruit and lentil production. • Caffeine treatment effects were observed under suboptimal growth conditions, but not under severe stress. • Both water deficit and holoparasitism by field dodder strongly negatively affected fruit and seed production. • Holoparasitism caused even more negative effects than water deficit on lentil production and the photosynthetic apparatus.