345:	Root invasion in the Milos catacombs.

Authors:	Rhizopoulou, Sophia(A)Psaras, George, K.(B)Kotzamanis, George(A)Nassios, Kostas(A)
Affiliations:	(A): Institute of General Botany, Department of Biology, University of Athens, Greece (B): Section of Plant Biology, Department of Biology, University of Patras, Greece
Presenter:	Rhizopoulou, Sophia , srhizop@biology.db.uoa.gr

Responses of roots to physical stimuli, like soil strength and climate are mediated via biochemical, physiological and anatomical processes. The case of roots invading fissures of pumice stone, in Milos catacombs (in the northern part of Milos island in Aegean, Greece) has been studied. It seems likely that the passage of roots through the soil affects the subsequent mechanical impedance. Catacombs’ digging and function as both a place of worship and burial ground, began in the turn of 1st Century AD. However, their existence was officially announced in 1840. These Catacombs consisted of an underground network of three chambers and a corridor (184 m long, 1.0-5.0 m wide and 1.7-2.5 m high), remained closed for more than 1,500 years. In our days, tourists can visit them. The dark, indoor environment is characterized by a high relative humidity (90-98 %) and a quite stable air temperature (20±3 °C), throughout a year. Several plant species growing in the surrounding environment, up on the hill (300 m a.s.l.), are mainly deeply rooted plants, characteristic of the Mediterranean flora. The roots, though, which do penetrate the roof of Catacombs, extending several meters parallel to the roof (4-20 m), reaching sometimes the ceiling level, exhibiting a growth rate 2.4-2.8 mm h-1, belong to Capparis spinosa L. In winter, the stone indoors is wet mostly by the extrusion of a solution (pH 5), from numerous thin lateral roots per square meter. The water potential of root apices is 0.4 MPa, approximately. The central cylinder consists of wide solitary vessels and the exodermis of several layers. Seasonal fluctuation in soluble sugars varies from 110 to 150 mg g-1 d.w., in starch 10-30 mg g-1 d.w. and in free proline 20-45 micro mol g-1 d.w.