Modification of root morphological parameters and root architecture in seedlings of Fraxinus ornus L. and Spartium junceum L. growing on slopes

ABSTRACT

A computerised image analysis system was used to investigate several root morphological parameters in young seedlings of broom (Spartium junceum L.) and manna ash (Fraxinus ornus L.) growing in three different environmental conditions: slope, terrace and plane. Data show that slope, to a greater extent than terrace, affects the root system of both species by increasing significantly the length and number of root apices of first-, second- and third- order lateral roots. Besides these variations in morphological parameters, the overall architecture of the root system results modified on a slope. In fact, an asymmetrical distribution of lateral roots was observed around the tap root and along two main directions: up-slope and down-slope. The morphological parameters, analysed separately on the two portions of the root system, present significant differences. The following hypothesis is put forward: in response to a slope, the two species reinforce their anchorage strain by changing the organisation of the root system, particularly in the up-slope direction. In these two species, the occurrence of slight differences in response to a slope suggests that plant anchorage might require species-specific adaptations.

KEY WORDS:

• root architecture
• slope
• Spartium junceum L.
• Fraxinus ornus L.