Stomatal density and leaf venation in Brassica: Mechanisms contributing to plant ecophysiology and agricultural sustainability

Background/Question/Methods

• Climate change including altered rainfall patterns and population growth is placing increased pressure on freshwater. The biggest consumer of freshwater is our agricultural system. Understanding the evolutionary dynamics and mechanistic basis of plant Water Use Efficiency (WUE) and other ecophysiological traits may lead to more water efficient crops and contribute to sustainable agricultural practices.
• The Brassica triangle includes six species and repeated hybridization yielding allotetraploids as well as multiple and parallel targets of artificial selection, resulting in an exceptional system to examine the evolution of the relationship between leaf structure and ecophysiological function.
• We compare patterns of leaf venation, stomatal density, and ecophysiological function including Water Use Efficiency (WUE) from six crop species that include turnips (B. rapa), cabbages (B. oleracea, B. rapa), oil seeds (B. oleracea, B. rapa, and B. napus), and mustards (B. juncea, B. carinata, and B. nigra), to test the hypothesis that hybridization and polyploidy can change patterns of phenotypic trait integration.

Results/Conclusions

• Across all taxa, abaxial and adaxial stomatal density is significantly correlated with WUE and stomatal conductance, but not photosynthetic capacity.
• Preliminary data did not reveal any significant correlations between leaf venation and WUE or other ecophysiological traits.
• Ongoing analyses based on an increased data set may indicate that phenotypic trait integration changes with ploidy level
• Phenotypic trait dis- and re- integration implies relatively evolutionary flexible traits that could be excellent targets for artificial selection aimed at decreasing water use and increasing agriculturally sustainable practices.
• Sustainable agroecological systems are a critical component of insuring future food security and environmental justice in the face of climate change and population growth.