Diversity in honey locust (Gleditsia triacanthos L.) seed traits across Danube basin

Abstract

Honey locust (Gleditsia triacanthos L.), in the past planted as ornamental, technical or forest tree, is presently considered as casually invasive tree in Danube basin. Since plant invasiveness is usually tightly associated with its reproduction biology, in this work we focused on characterization of seeds from honey locust populations across this area. Analysing seed coat colour, thousand seeds weight (TSW), seed projection area, seed thickness, percentage of germinated seeds and their germination energy, as well as portion of seeds infested by honey locust seed beetle (Megabruchidius tonkineus), consumed part of seeds and their germination ability in relation to seed characteristics, local temperature means and precipitation sums during vegetation period, we came to the following conclusions: seed coat colour diversity decreases with geographical latitude; TSW, seed projection area and thickness were negatively correlated to mean temperature and positively to precipitation sum; between percentage of naturally germinated seeds and TSW as well as seed thickness we found positive correlations; germination energy showed positive relation to mean temperature and a negative one to precipitation sum; and the same relations were observed for infested seeds percentage and consumed seed part. No infested seed was able to germinate. From these results we can conclude that in colder and wetter conditions higher seed germinability, and in warmer and drier conditions enhanced germination energy of seeds supports spreading of this tree species. However, honey locust seed beetle can significantly affect seed germinability in regions with warm and dry summers.