Juvenility and flowering in Festuca pratensis Huds. 2. Effect of light intensity, defoliation and duration of primary induction treatments
1996
Havstad, L.T. (Planteforsk - Norsk Inst. for Planteforskning, Apelsvoll Forskingssenter, Grimstad (Norway). Avd. Landvik)
Seedlings of Festuca pratensis Huds. (cv. Salten) were raised at three different light intensities (141, 85 or 28 mmol m-2s-1 ) for 7 weeks after emergence and then either left uncut or defoliated 40 or 80 of total leaf area (100, 60 or 20 of leaf area left), before transfer to primary induction (6oC, natural short days for 12, 15 or 18 weeks). Increasing light intensity enhanced tillering and leaf production during plant raising and elevated the content of water-soluble carbohydrates, in both shoots and roots, at the start of primary induction. Plants from the lowest light intensity continued to have the lowest tiller number also during primary induction. Defoliation at the start of induction reduced subsequent tillering and leaf production and regrowth was too slow for defoliated plants to overtake intact plants even after the longest induction period. Registration of flowering characters, after exposure to 15OC and continuous light (secondary induction), revealed that the percentage of heading plants generally was more affected by the duration of primary induction than by light intensity or defoliation prior to induction. Thus there was no significant effect of plant size at the start of induction on the flowering ability, no indication of a distinct juvenile stage were found in seedlings of Festuca pratensis. Defoliation had less influence on the number of panicles per plant than light intensity and, in particular, the duration of primary induction. An additional tagging experiment revealed that some tillers even developed after primary induction became reproductive, supporting suggestions from the first experiment in this series that tillers of Festuca pratensis lack or have an extremely short juvenile stage.
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