The Pearson bilateral correlation shows that the aerial part dry weight is positively correlated with the permeability, porosity, and water-holding capacity and negatively with the bulk density and density at saturation, whereas the short root production is negatively correlated with the permeability and water-holding capacity. In contrast to sand and hydroponic media, the sawdust medium stimulates the phloem/xylem ratio, the root architecture, and the short roots. However, the sand medium increases the main root dry weight by the radial expanse stimulation at the level of the epidermis, vascular cylinder, and cortex and compensates the less root architecture by the stimulation of the xylem and phloem areas.

The growth of the seedling is strongly stimulated by the hydroponic medium through the stimulation of the aerial part dry weight and the main root length. We examined the impact of five different hydromechanical medium properties (hydroponics, vermiculite, vermiculite-gravel, sawdust, and sand) on the morphology, physiology, and anatomy of Cedrus atlantica seedlings at a controlled growth chamber. The biomechanical root flexibility in response to hydromechanical soil heterogeneity is the most determining factor of the root architecture which plays a paramount role in mycorrhizal infection and allows the seedlings to adapt to the environmental constraint. However, dry matter pro- duction over the course of the experiment was apparently unrelated to the extent of mycorrhizal infection, whether mea- sured by percent of roots tips that were mycorrhizal or the quantity of viable mycelium per root ( Figure. Mycorrhizal infection had no significant effect on plant dry weight, except in the case of plants fertilized with 5.0 mM NH 4 + before inoculation (Table 1). Within N sources, N concentration did not significantly affect root my- celium content ( Figure 3B). ced- rorum mycelium in roots of NO 3 − -treated seedlings averaged four times that in NH 4 + -treated plants ( Figure 3B). The concentration of N supplied before inoculation did not affect the percentage of root tips that became infected.

Forty percent of root tips were infected in the NO 3 − treatments, compared to less than 10% in the NH 4 + treatments ( Figure 3A). inoculated plants became mycorrhizal, whereas none of the uninoculated control plants did.

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