Submitted to: Functional Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/30/2008
Publication Date: 2/1/2009
Citation: Richards, J.H., James, J.J., Drenovsky, R.E., Christman, M.A. 2009. ENVIRONMENTAL STRESS AND GENETICS INFLUENCE NIGHTTIME LEAF CONDUCTANCE IN THE C4 GRASS DISTICHLIS SPICATA. Functional Plant Biology 36:50-55
Interpretive Summary: Water loss by C3 and C4 plant at night appears wasteful since plants cannot fix carbon through photosynthesis during these periods. We examined the degree to which soil salinity and genetic variation influenced the magnitude of water loss during the night period by the C4 grass Distichlis spicata. While genotypes exhibited large differences in magnitude of water loss, increasing soil salinity did not affect the magnitude of night time water loss in the bulk of genotypes evaluated. This indicates genetic variation among populations may be a larger driver of plant community water use at night than environmental stresses such as salinity. Understanding these patterns can help refine understanding of plant community water use and drivers of night time water loss by plant communities.
Technical Abstract: Growing awareness of nighttime leaf conductance (gnight) in many species, as well as genetic variation in gnight within several species, has raised questions about how genetic variation and environmental stress interact to influence the magnitude of gnight. The objective of this study was to investigate how genotype salt tolerance and salinity stress affect gnight for saltgrass (Distichlis spicata (L.) Greene). Across genotypes and treatments, nighttime water loss rates were 5-20% of daytime rates. Despite growth declining 37-87%, neither of the high salinity treatments (300 mM and 600 mM NaCl) had any effect on gnight in 4 of the 6 genotypes compared with a 7 mM NaCl control treatment; daytime leaf conductance (gday) was also not affected by salinity treatment in all but one of these genotypes. There was no evidence that more salt tolerant genotypes (assessed as ability to maintain growth as salinity increased) had a greater capacity to maintain gnight or gday at high salinity. However, gnight as a percentage of gday was unaffected in the three most salt tolerant genotypes. While gnight in the 7 mM treatment was always highest or not different compared with the 300 mM and 600 mM treatments, gday was generally highest in the 300 mM treatment, indicating separate regulation of gnight and gday in response to an environmental stress. Surprisingly, gnight was negatively correlated with A among genotypes in the 7 mM and 600 mM treatments, although no relationship was found in the 300 mM treatment. Thus, it is clear that genetics and environment both influence the magnitude of gnight for this species. Combined effects of genetic and environmental factors such as were investigated here are likely to impact our interpretation of variation of gnight in natural populations and, when accounted for, may improve our ability to assess costs and benefits of gnight.