Improvement of root architecture under abiotic stress through control of auxin homeostasis in Arabidopsis and Brassica crops

Auxin plays an important role in many aspects of plant development including stress responses. Here we briefly summarize how auxin is involved in salt stress, drought (i.e. mostly osmotic stress), waterlogging and nutrient deficiency in Brassica plants. In addition, some mechanisms to control auxin levels and signaling in relation to root formation (under stress) will be reviewed. Molecular studies are mainly described for the model plant Arabidopsis thaliana, but we also like to demonstrate how this knowledge can be transferred to agriculturally important Brassica species, such as Brassica rapa, Brassica napus and Brassica campestris. Moreover, beneficial fungi could play a role in the adaptation response of Brassica roots to abiotic stresses. Therefore, the possible influence of Piriformospora indica will also be covered since the growth promoting response of plants colonized by P. indica is also linked to plant hormones, among them auxin.

Promoting mixed stands through conversion treatments. Effect of holm oak coppices thinning on black pine regeneration

The effects of conversion treatments, depending on ecological factors and silvicultural parameters (thinning intensity, thinning type and rotation, among others) have been studied during the last fifteen years in an experimental trial in Central Spain. The general climate is continental Mediterranean; soils are low depth and limy; vegetation is an homogeneous dense coppices of Quercus ilex with isolated Pinus nigra trees. The experimental design (three locations) includes different thinning intensities (from 0 to 100% of extracted basal area). Inventories have been carried out in 1994 and 2010; thinning treatments were done in 1995 and 2011. Analysis of the effects of the conversion treatment show the increment of diameter and height growth rates, the canopy recovery and the stand resprouting, finding differences in these effects between thinning treatments. Besides the induced changes at holm oak stand, the application of conversion treatment clearly changed the woodland dynamics. Fifteen years after the thinnings, floristic composition varied and an abundant pine regeneration was installed in the woodland. In this work we describe the changes between inventories in tree species composition and diameter distribution, specially in the case of black pine. The conversion treatment caused changes in forest dynamics in the short term, increasing biodiversity and diversifying the forest structure. The fast installation of Pinus regeneration suggests the potential of the zone for the establishment of multipurpose mixed Quercus-Pinus stands in wide areas where Quercus species were favoured by human populations for firewood production. Conversion treatment of coppices, with the creation of mixed stands, constitutes a good management alternative for extensive areas and an interesting technique to adaptation to global change.