Effects of Water Shortage and Air Temperature on Seed Yield and Seed Performance of Lucerne (Medicago sativa L.) in a Mediterranean Environment

Abstract

Seed production and performance of lucerne is characterized by fluctuating yields with often poor seed quality, and is dependent on environmental conditions, genetic characteristics and agronomic techniques applied during seed set, development, maturation and storage. A field experiment was carried out in two successive growing seasons at Kopais (southern Greece) to evaluate the effects of drought stress imposed by three irrigation treatments, and temperature during flowering and seed filling on lucerne seed yield and quality. Plant water status, expressed in terms of the water potential index (WPI), growth in leaf area and dry weight, seed yield and yield components, flowering and seed quality parameters were measured throughout the growing seasons. The adopted irrigation schemes produced a clear differentiation among treatments concerning their plant water status. Seed yield and leaf growth showed close positive correlations with WPI. An irrigation effect was also detected for the number of pods/plant, but not for the average weight of seeds/pod. Less negative values of WPI, and, especially, higher temperatures during flowering were also positively associated with a longer duration of flowering, as well as with higher total numbers of inflorescences. A very good description of the time course of seed germination was performed by fitting the Richards’ function to the real data. By examining the germination parameters derived from this function it was found that final germination and germination rate were improved, while germination duration was shortened with more negative values of WPI. The effects of growing season and seeding period were occasionally equally or more important than irrigation effects. These results are also discussed in terms of their practical implications for seed producing lucerne crops.

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