Halophytic plants are characterized by enhanced growth under saline conditions. A recent study in Annals of Botany combines physiological and anatomical analyses to identify processes underlying growth responses of the mangrove Avicennia marina to salinities ranging from fresh to seawater conditions.
Following pre-exhaustion of cotyledonary reserves under optimal conditions (50% seawater), seedlings of A. marina were grown hydroponically in dilutions of seawater amended with nutrients. Whole-plant growth characteristics were analysed in relation to dry mass accumulation and its allocation to different plant parts. Gas exchange characteristics and stable carbon isotopic composition of leaves were measured to evaluate water use in relation to carbon gain. Stem and leaf hydraulic anatomy were measured in relation to plant water use and growth.
The results identified stem and leaf transport systems as central to understanding the integrated growth responses to variation in salinity from fresh to seawater conditions. Avicennia marina is revealed as an obligate halophyte, requiring saline conditions for development of the transport systems needed to sustain water use and carbon gain.