Phenological responses to temperature of an annual and a perennial Lesquerella species

Background and Aims The annual Lesquerella fendleri, native to the south-western desert of United States and Mexico, and the perennial L. mendocina, native to Argentina, may have potential as new crops for cold-arid environments. The introduction of a new crop requires an understanding of environmental influences on growth and development, particularly temperature, which has been recognized as the main factor affecting the rate of development in crops. The objective of this study was to examine differences in the phenology of L. fendleri and L. mendocina and in the response to temperature in both vegetative and reproductive phases. Methods Plants of each species were grown at a range of constant temperatures under controlled conditions and developmental responses were analysed and quantified. Key Results The rate of development of L. fendleri increased linearly with temperature in the phase from emergence (EM) to floral bud appearance (FBA) over the range 9-20 degreesC, and for the phase from FBA to first flower open (FL) over the range 9-24 degreesC. In contrast, the rate of development of L. mendocina was insensitive to temperature during the phase EM to FBA. In the phase FBA to FL, L. mendocina had a lower sensitivity to temperature than L. fendleri. In addition, L. fendleri exhibited a quantitative response to supra-optimal temperatures (reducing rate of development with further increases in temperature) whereas L. mendocina showed a qualitative response, with development ceasing to progress at temperatures above the optimum. Conclusions This differential behaviour at high temperatures could explain the biennial habit found for L. mendocina sown during late spring under field conditions, whereas it behaves as an annual when sown in autumn-winter. The possibility is discussed of using this information for establishing the coincidence of critical stages with environmental conditions that can limit potential and actual yield through agronomic practices. (C) 2004 Annals of Botany Company.