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

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, var. Anatone and var. Columbia, selected for higher reproductive culm production. Clipping induced a stronger direct compensatory reproductive photosynthetic response in basal florets of Anatone compared to Columbia germplasm individuals, with no indirect compensatory response apparent 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 increased flowering culms may alter reproductive herbivory tolerance, a feature important in the convergence of herbivory and drought tolerance traits. 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.