Developmental Responses to Temperature and Photoperiod in Ecotypes of Medicago polymorpha L. Collected Along an Environmental Gradient in Central Chile

Abstract

The phenological development of nine Chilean accessions of Medicago polymorpha, collected along a north±south aridity gradient, and of two commercial cultivars of the same species, were compared in 12 sequential outdoor sowings at Cauquenes (35858 H S, 72817 H W, elev. 177 m), in the sub-humid Mediterranean climate zone of Chile. A glasshouse experiment was also conducted to evaluate the eect of photoperiod on phenophase timing. There was a clear gradient in precocity among the Chilean accessions in both experiments: accessions MPO-9-88 and MPO-7-88, from the arid zone, were the earliest-¯owering accessions, whereas MPO-36-88 from the humid Mediterranean zone was the latest. Both experiments revealed signi®cant variation among the Chilean accessions in the response of owering time to variation in photoperiod regime. Dierences in days to¯owering between the least-(8 h) and the most-(16 h) inductive photoperiods were lower in precocious accessions from arid and semi-arid zones, than in lateowering accessions from more humid zones. Rate of progress to¯owering, de®ned as the inverse of time from emergence to ®rst¯ower appearance (1/f), was related to mean diurnal temperature, or to both mean diurnal temperature and mean photoperiod. In two early-¯owering accessions from the arid zone, and in the Australian cultivar`Circle Valley', 1/f was aected signi®cantly (P 5 0 . 05) by both temperature and photoperiod. In the remaining accessions, no signi®cant responses to temperatures were detected; 1/f was in¯uenced signi®cantly by photoperiod only.# 2000 Annals of Botany Company

Differential and interactive effects of temperature and photoperiod on budburst and carbon reserves in two co‐occurring Mediterranean oaks

“…However, this sensitivity varies across species, either due to genetic or to environmental factors (Lechowicz 1984; Myking & Heide 1995; Bertero et al. 2000; del Pozo et al. 2000).…”

Phenology, leaf gas exchange, growth and seed yield in Medicago polymorpha L. populations affected by water deficit and subsequent recovery

“…Flowering time appears to be a common adaptive trait in annual legumes along aridity gradients, provided that they have sufficient seed dormancy (Ehrman and Cocks, 1990). Photoperiod requirements for the induction of flowering may decrease with increasing aridity and rainfall unpredictability (Aronson et al, 1992;Del Pozo et al, 2000). Our study showed that water deficit significantly delayed the time to first flower bud and accelerated the time to physical maturity only in the populations from middle and wet climate regions.…”

“…This plant is considered as a potential species for pasture improvement in the Mediterranean regions (Sheaffer et al, 2002). The species is also widespread in regions with Mediterranean-like conditions in Australia, Chile, South Africa and the United States (Del Pozo et al, 2000;Nichols et al, 2007). Observations of M. polymorpha at natural sites show that it is well adapted to neutral and slightly acid soils (Reid et al, 1989).…”

Phenology, leaf gas exchange, growth, and seed yield in contrasting Medicago truncatula and Medicago laciniata populations during prolonged water deficit and recovery

“…Optimum flowering time is a major component of crop environmental adaptation (Subbarao et al 1995). Flowering time appears to be a common adaptive trait in annual legumes along aridity gradients, provided that they have sufficient seed dormancy (Ehrman and Cocks 1990;Piano et al 1996). Del Pozo et al (2000 reported that the difference in flowering time among accessions of Medicago polymorpha is explained by differential sensitivity of ecotypes to photoperiod and temperature.…”