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Temperature and Photoperiod Effects on Multifoliolate Expression and Morphology of Alfalfa

Estacian Experimental INTA, Anguel, LaPampa, Argentina
Dep. of Agronomy and Plant Genetics, 1991 Upper Buford Circle
USDA-ARS, Univ. of Minnesota, St. Paul, MN 55108

^* Corresponding author.

Alfalfa (Medicago sativa L.) cultivars with multifoliolate (MF) leaves are being promoted as a source of high quality forage, but information is lacking about the effect of environment on MF expression. We studied the influence of air temperature and photoperiod on the MF trait and its association with leaf and stem morphology. We grouped plants from four cultivars into four MF expression classes (very low, <10%; low, 10–29%; medium, 30–60%; and high, >60% MF leaves). These plants were grown in four growth chamber environments combining cool (20/11 °C day/night) and warm (29/17 °C) air temperatures with short (13 h) and long (16 h) photoperiods. Photoperiod had greater influence than temperature on MF expression (MF%, number of MF leaves total leaf number^–1). Under long-days, MF expression of plants in very low, low, and medium MF expression classes declined linearly with increased maturity. Under short-days, MF% of these classes declined until bud, but then increased until maturity. Multifoliolate expression of plants in the high expression class decreased in the cool-long day environment, but maintained or increased MF% in other environments. At harvest, MF%, leafiness, and leaflet number per MF leaf were greater for short vs. long photoperiods, but were not affected by air temperature. Multifoliolate expression was positively correlated (r = 0.43) with leafiness and number of leaflets per MF leaf (r = 0.96), but was not correlated with stem characteristics. Individual MF leaves had larger leaf area but similar specific leaf weight as trifoliolate leaves in all environments. In evaluation of MF expression, stage of maturity, and environmental conditions should be standardized.

Received for publication April 9, 1992.