Somatic embryogenesis (SE) is a complex biological process regulated by several factors, such as the action of plant growth regulators, namely auxins, of which the most physiologically relevant is indole-3-acetic acid (IAA). In tamarillo, an optimized system for induction of SE creates, after an induction process, embryogenic (EC) and non-embryogenic callus (NEC). In this work the endogenous levels of auxin along the induction phase and in the calli samples were investigated using chemical quantifications by colorimetric reactions and HPLC as well as immunohistochemistry approaches. Differential gene expression (IAA 11, IAA 14, IAA 17, TIR 1, and AFB3) analysis during the induction phase was also carried out. The results showed that the endogenous IAA content is considerably higher in embryogenic than in non-embryogenic calli, with a tendency to increase as the dedifferentiation of the original explant (leaf segments) evolves. Furthermore, the degradation rates of IAA seem to be related to these levels, as non-embryogenic tissue presents a higher degradation rate. The immunohistochemical results support the quantifications made, with higher observable labeling on embryogenic tissue that tends to increase along the induction phase. Differential gene expression also suggests a distinct molecular response between EC and NEC.

Almond (Prunus dulcis (Mill.) D. A. Webb) is a traditional culture in Portugal, which gained a renewed interest due to the installation of new orchards. Grafting remains the main method used for almond propagation. The successful establishment of a graft union between two parts (scion and rootstock) requires auxins, which are involved in wound response and vascular regeneration. This work aimed at the quantification and immunolocalization of indole-3-acetic acid (IAA) in almond micrografts before micrografting (T0) and 21 days after micrografting (T2). The results are a step forward to understand of how auxin is involved in graft compatibility in almond.

In recent years, almond culture has increased in Portugal with the introduction of new orchards neglecting the traditional varieties. Micrografting, grafting in in vitro conditions, is a technique that has been established for commercial almond trees, but no studies have been described with Portuguese varieties. In this work, an efficient protocol for almond micrografting with traditional almond trees was established. The effect of plant growth regulators (BAP and IBA) and activated charcoal on culture medium were also evaluated during micrografting assays. Furthermore, the effect of auxin IBA on root induction was analysed during rooting assays.