Relationships between reproductive output, morpho-physiological traits and life span in Lesquerella (Brassicaceae)

The development of perennial industrial crops could contribute to increase agriculture sustainability and yield stability in arid environments. Since perennial plants allocate resources preferentially to perpetuation and to structural and functional characters that provide drought tolerance, they tend to have lower reproductive output (yield) than their congeneric annuals. Four species of Lesquerella native to arid regions were evaluated to understand the relationships between reproduction, drought tolerance, and their association with the plant's life span. We assessed the following set of characters (defined as plant strategies): phenology, gas exchange, specific leaf area, leaf area ratio, total biomass and biomass allocation. Annual (Lesquerella gracilis and Lesquerella angustifolia) and perennial (Lesquerella mendocina and Lesquerella pinetorum) species were compared under water limiting conditions. Within this set of species differences in structural and functional characters were observed. The annual, L. gracilis showed a plant strategy characterized by high reproductive output, harvest index (HI) and specific leaf area (SLA). L. mendocina (perennial), produced more total biomass, but had a low reproductive output, and also showed characters that provide drought tolerance (high allocation to roots-root mass ratio (RMR), and storage-total non structural carbohydrates (TNC) and low SLA). The annual L. angustifolia and the perennial L. pinetorum had intermediate plant strategies (i.e. intermediate values of traits typically related with annual or perennial life span). In the case of L. pinetorum we found some traits common to L. mendocina: long vegetative period, high biomass, CO₂ assimilation rate (A), and water use efficiency (WUE), and low SLA. The high reproductive output in L. pinetorum was a result of both, higher total biomass and longer growing season compared to the annuals, and of higher HI in relation to the other perennial. These differences in plant strategies among perennial Lesquerella show that there are different combinations of traits that could be used as criteria for the selection of a perennial crop in programs of domestication for Patagonia and others arid lands.