Morpho-histological analysis of tomato (Solanum lycopersicum L.) plants after treatment with juglone

Juglone is a substance that limits plant growth and has a toxic effect on plant development. In this study, we analyzed the influence of juglone at two different concentrations (10−3 M and 10−4 M), which were applied to different parts of Solanum lycopersicum L. plants (root system, stem after decapitation, and surface of a younger leaf or after autografting) for a short period of time (7 days), on the morphology and histology of stems. At a lower concentration, juglone had positive effects on plant growth, which resulted in an increase in interfascicular cambial cell divisions, faster development of a continuous cambium layer along the stem circumference, and development of fibers. Additionally, under the influence of juglone, the number of developing leaves increased and adventitious roots developed. The results are discussed based on the current literature concerning the reaction of plants to juglone and to stress conditions.