Root growth and resource allocation in seedlings of two mezcal agave species under salt stress

Abstract

Soil salinization is a problem that grows every year and is accentuated in arid and semi-arid zones, particularly areas with irrigated agriculture. To cope with this stress, desert plants have developed a variety of responses, including the modification of the architecture of their root system. However, the inclusion of root phenotypic traits in plant breeding programs hasn't been considered in most studies, so little is known about how the roots of desert plants respond to salinity stress and whether their cultivation is viable in saline soil. Within the arid and semi-arid environments, the genus Agave is endemic to the Americas, and wild and cultivated species have been used to obtain mezcal and tequila, plus several other traditional products. In this work we studied the early growth of two in vitro cultivated Agave species under salt stress (NaCl). We have determined that Agave angustifolia is tolerant to salinity, while A. marmorata is resilient to it. Although salt stress reduced the biomass of A. marmorata plants, it was found that at higher salinity the primary root grew larger than the adventitious roots. Moreover, we found that under salt stress, growth is oriented more towards the shoot rather than the root. Thus we propose that the differential growth of root types and resource partitioning would be important components in the response of salt stress, worth investigating for Agave breeding and conservation.