Comparative and functional anatomy of parasitic and non-parasitic species of Santalales

Abstract

The order Santalales is the group in which is found the largest and most diverse lineage of parasitic plants. In this order, there is a great myriad of forms, from non-parasitic groups to virtually all expressions of parasitism in plants, including root hemiparasites, stem hemiparasites, root holoparasites, and even endoparasites. Despite the great diversity observed in the group, little is known about wood structure of these species and water relations with their hosts, with the exceptions of a few species, non-representatives of the order. This is due to the lack of studies, especially with a comparative approach, discussing topics related to functional wood traits in this group. It is in this context that our work is inserted, having as a main objective better understand the functional relationship of the parasite-host model using wood anatomy as a base. With this purpose, we intend to use vegetal anatomy techniques such as light microscopy and electron microscopy to understand the wood structure and anatomy of different representatives, both parasites and non-parasites, of the order. In combination with the anatomy techniques, empirical and theoretical methods will be utilized to investigate the water relations aspects of the host-parasite interaction, such as conductivity and vulnerability of the vascular system. This way, the present project aims to combine a variety of methodologies to better understand the wood structure and its relation to its function in the host-parasite hydraulic model. For this, the wood anatomy and structure of various groups within the order will be investigated to determine if there is a general anatomical pattern and if there are changes associated with the acquisition of parasitic habit. We also intend to investigate the conductivity of their woods, especially in the parasitic species, as well as their haustorial connections. Our initial hypotheses are that there should be a group of anatomical wood features associated with the parasitic habit, conferring high efficiency and safety to these species and that haustorial systems with multiple connections should have greater efficiency as a whole than haustorial systems with solitary connections. (AU)