Germination Response of Subterranean, Berseem, and Rose Clovers to Alternating Temperatures

Abstract

Annual clover (Trifolium spp.) stands are sometimes poor because of low and slow germination due to unfavorable temperatures. The study was conducted to identify optimum temperature for germination of relatively new clover species to the U.S. Southeast to improve stand establishment. High temperature germination was also examined to estimate summer germination which usually results in seedling mortality and a decrease of the soil seed‐bank. Seed of 10 cultivars of T. alexandrinum L., T. brachycalycinum Katzn. and Morley, T. hirtum All., T. subterraneum L., and T. yanninicum Katzn. and Morley were subjected to alternating 12 h day/12 h night temperatures of 15/5, 20/10, 25/15, 30/20 and 35/25 °C. Germination counts were made at 3, 6, 9, and 12 d to determine percent germination and germination rate index (GRI). Germination was >80% for all entries at the three lowest temperature treatments except ‘Larisa’ subclover at 25/15 °. At 30/20 °C, germination of ‘Bigbee‘ berseem and T. brachycalycinum subclovers decreased to 54 to 66%, while the other species decreased to <35%. The 35/25 °C treatment suppressed germination to <25%. The optimum temperature for GRI was 25/15 followed by 20/10, 15/5, 30/20, and 35/25 °C. The optimum germination temperature of 25/15 °C occurs in October along the Texas‐Louisiana Gulf Coast. September plantings (30/20 °C) in this area should be limited to T. alexandrinum and T. brachycalycinum species. Cultivars that germinate at summer temperatures of 35/25 °C or higher should be avoided unless they have a high hard‐seed content.

How Winter Annual Forage Legumes Persist In Diverse Soil Moisture Environments of a Semi-arid Region

“…Later maturing species or cultivars might have more available soil moisture, but also are exposed to higher temperatures possibly leading to reduced seed yield and quality (4). Establishment and maintenance of a soil seed‐bank, thus, becomes more critical (1,4).…”

“…Differences did exist among species in date of uniform germination (Table 4). The differences among berseem, rose, and arrowleaf clovers (Table 4) are consistent with the findings of Evers (4). Beuselinck et al (1), Evers (4), and Fairbrother and Pederson (5) all stated that stand persistence of small‐seeded cool‐season annual legumes, such as those in the present study, was dependent on hardseededness that establishes a soil seed‐bank to overcome times of less than optimum environmental conditions.…”

“…Seed production is critical to building a soil seed‐bank for sustaining stands of annual species (1,4). Earlier maturing species (Table 4) can take advantage of winter precipitation and cooler temperatures during spring in temperate or subtropical Mediterranean climates (2,12).…”

“…In temperate or subtropical continental climates having warm, dry winters (9), however, early maturity might occur during periods of low precipitation, reducing seed yield and quality. Later maturing species or cultivars might have more available soil moisture, but also are exposed to higher temperatures possibly leading to reduced seed yield and quality (4). Establishment and maintenance of a soil seed‐bank, thus, becomes more critical (1,4).…”

Effects of day-night temperature combinations under constant day length on emergence and early growth of sericea lespedeza genotypes

“…Species whose seedlings emerge fast and grow rapidly can be more competitive than slow emerging and growing seedlings (Wright et al 1978). Temperature is a major factor that determines the span of time from sowing to seedling emergence (Evers 1991;Brar et al 1991). However, the effects of temperature on germination vary among species and genotypes (Ellis et al 1986;Evers 1991;Brar et al 1991;Hill and Luck 1991).…”