Variation in reproductive photosynthetic compensation of distinct germplasm varieties of a native rangeland grass, Pseudoroegneria spicata, following floral defoliation

Authors: Quigley, Kathleen; O'Connor, Rory; Monaco, Thomas; Hamerlynck, Erik

Submitted to: Conservation Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/7/2024
Publication Date: N/A
Citation: N/A

Interpretive Summary: Perennial sagebrush steppe bunchgrasses can increase photosynthesis in their florets after these have been defoliated, and this activity helps seeds develop in the remaining undisturbed florets. This kind of response might be a convergent trait, allowing the plant to be adapted to both herbivory and drought, but as to which of the two is most important isn’t clear. So, we used cultivars of bluebunch wheatgrass that had been selected for drought tolerance (Anatone) and compared their response to floret defoliation to a cultivar selected for greater reproduction (Columbia). We found that drought-tolerant Anatone had a stronger compensatory photosynthetic response compared to Columbia, a finding that suggests selection for drought tolerance might impart herbivory tolerance in this grass’s reproductive structures. This information could be valuable in plant material selection and development for restoration efforts in sagebrush steppe.

Technical Abstract: Understanding plant ecophysiological functioning is critical in formulating effective ecologically-based strategies to conserve and enhance resiliency and resistance in sagebrush steppe, as well as improving their restoration following degradation by interactive effects of climate change, wildland fire, and invasive annual grasses. Recent research has shown increased reproductive photosynthesis following floral defoliation can be important to reproductive potential, yet how this is expressed in plant material selected for different functional attributes is unknown. To address this, we measured photosynthetic gas exchange in clipped and unclipped basal florets and flag leaves of two germplasms of the native perennial bunchgrass, bluebunch wheatgrass, one selected for drought tolerance (var. Anatone), and one for enhanced reproduction (var. Columbia). Clipping induced a stronger direct compensatory reproductive photosynthetic response in basal florets of Anatone compared to Columbia germplasm individuals, with no indirect compensatory response in unaffected distal florets of either germplasm. Flag-leaf photosynthesis did not differ between the germplasm lines, but Columbia flag leaves did show evidence of increased photosynthesis on culms with clipped basal florets. These findings suggest selection for drought tolerance may result in reproductive photosynthetic trait convergence that enhances reproductive herbivory tolerance. Such information could help in planning effective seed mixes to enhance population stability across highly variable sagebrush steppe ecosystems, as well as directing future plant material selection to improve restoration success in these economically important rangelands.