Flowering regulation in the facultative biennial Oenothera biennis L.: Environmental effects and their relation to growth rate

Abstract

a b s t r a c tThe lifecycle of the facultative biennial oilseed-crop evening primrose (Oenothera biennis) is a major constraint for its commercial production under different growing conditions, as a variable proportion of plants fails to flower during the first season and remains as vegetative rosettes (biennial behavior). The aim of this work was to understand how flowering is regulated in this species and to identify the main determinants of its biennial behavior.Different planting dates and manipulative treatments (seed vernalization, photoperiod extension and fertilization) were employed to analyze if: (i) biennial behavior occurs when obligate requirements for vernalization or photoperiod are not satisfied; and (ii) responses to these environmental cues depend on the size and/or growth rate of rosettes.Our results indicate that O. biennis has an obligate long-day requirement for flowering and a facultative vernalization response. There is no minimum size requirement for vernalization response (as very small seedlings responded to the vernalization treatment) and the rate of development toward flowering under inductive photoperiods was strongly affected by rosette's growth rate. The incidence of high temperatures just before the onset of reproduction is proposed as an inhibitory factor that prevents reproduction under otherwise photo-inductive conditions. This last factor would explain the high incidence of biennial behavior frequently observed in spring/summer sowing in this crop.

Photoperiod–temperature phase lag: A universal environmental context of seasonal developmental plasticity

“…The most prominent examples are the promotion of flowering by long‐day after vernalization. The response has been reported in Brassicaceae including Arabidopsis thaliana (Andreés & Coupland, ), Cardamine occulta (Kudoh, Ishiguri, & Kawano, ), other dicots (e.g., Oenothera biennis Giménez, Sorlino, Bertero, & Ploschuk, ) and monocots (e.g., wheat and barley Ream, Woods, & Amasino, , and Brachipodium distachyon Woods, Ream, & Amasino, ). As it is expected from Figure a, the repression through the temperature control is likely to be released in early winter.…”

Growing evening primroses (Oenothera)

“…Higher temperatures such as 24°C ( Glick and Sears, 1994 ; Johnson et al, 2009b ) are tolerated and can even promote growth. They should, however, not exceed 27°C since for example bolting may be prevented ( Yaniv et al, 1989 ; Clough et al, 2001 ; Giménez et al, 2013 ; but also see von Arx et al, 2012 ). Plants start to develop the first true leaves 7 – 10 days after germination at a plant size of 2.0 – 2.5 cm diameter.…”

“…In general, production of successive flowers depends on day-length and terminates in short-day conditions, i.e., at the end of a field season but not in long-day greenhouse conditions. For growth schemes of Oenothera cultures under various conditions see, e.g., Kachi and Hirose (1983) ; Gross and Kromer (1986) , Russell (1988) ; Reekie and Reekie (1991) , Fieldsend and Morison (2000b) ; Clough et al (2001) , Deng et al (2001) ; Fieldsend (2004) , Honermeier et al (2005) , Vilela et al (2008) , or Giménez et al (2013) .…”

“…Alternating cold–warm treatments are more effective than continuous cold ( Chouard, 1960 ; Picard, 1965 ). Seed vernalization seems to be ineffective ( Chouard, 1960 ; Picard, 1965 ; but also see Thomas and Vince-Puce, 1997 , p. 161; Deng et al, 2001 ), but some vernalization response was observed in seedlings by Giménez et al (2013) . In some materials, predisposition for vernalization starts 30 days after germination, which corresponds to the end of the early rosette stage described earlier, peaks after 56 and again after 180 days ( Müller-Stoll and Hartmann, 1959 ; reviewed in Chouard, 1960 ; Takimoto, 1985 ).…”

Caracterización seminal y del desarrollo de Oenothera rosea L’Hér. ex Ait. en invernadero

“…ex Link y O. suaveolens Pers. se han descrito, debido a que sus plantas en maceta ya se comercializan (Chouard, 1960;Clough, E. A., Cameron, A. C., Heins, R. D., y Carlson, 2001;Clough, E. A., Cameron, A.C., Heins, R. D., y Carlson, 1999;Ensminger, P. A., y Ikuma, 1987;Giménez, R., Sorlino, D. M., Bertero, H. D., y Ploschuk, 2013;Picard, 1965).…”