Low temperature influence on flowering in Citrus. The separation of inductive and bud dormancy releasing effects

Abstract

The flowering response of Owari Satsuma mandarin (Citrus unshiu Marc) to low temperature treatments has been determined using potted trees and in vitro bud cultures. In potted trees the chilling treatments released bud dormancy and enhanced both sprouting and flowering, but these two responses could not be separated. However, bud cultures showed no dormancy, and a specific effect of low temperature on flower induction was demonstrated. Low temperature appears to have a dual effect, releasing bud dormancy and inducing flowering. Potential flower buds have a deeper dormancy than vegetative buds, and the first stages of flower initiation seem to occur before the winter rest period.

PtFLC homolog from trifoliate orange (Poncirus trifoliata) is regulated by alternative splicing and experiences seasonal fluctuation in expression level

“…The Xowering response usually shows a quantitative relationship with the duration of exposure to chilling temperatures (García-Luís et al 1992;García-Luís and Kanduser 1995;Chaikiattiyos et al 1994). This relationship suggests that prolonged exposure to low temperatures might be one of the important environmental cues for Xoral induction in citrus (Nishikawa et al 2007).…”

“…Compared with annual plants, Xoral transition in perennial plants is initiated in the Wrst growth season, but the development of Xowers is arrested during the winter to ensure production of mature Xowers the next spring compare with annual plants. In addition, many perennial plants require exposure to low temperatures before active shoot growth or Xower development can resume the next growing season (Lona 1968;Perry 1971;García-Luís et al 1992). Owing to the diYculties of genetic and molecular analysis in perennials, the molecular mechanisms underlying the process are unclear to date.…”

“…Most citrus species usually show two to three, rarely more, Xushes of bud sprouting throughout the year (Davenport 1990); the spring Xush is the most important one for Xower bud formation because of the plants' response to the low winter temperature (García-Luís et al 1992). The Xowering response usually shows a quantitative relationship with the duration of exposure to chilling temperatures (García-Luís et al 1992;García-Luís and Kanduser 1995;Chaikiattiyos et al 1994).…”

“…Previous studies suggest that a large portion of the promotion of Xowering by vernalization is achieved through downregulation of FLOWERING LOCOUS C (FLC) mRNA level by cold. However, in perennials, especially those of temperate and subtropical regions, there is great variation between perennial and annual plants in induction of Xowering, development of inXorescence, and Xowering; for example, a delay exists between Xoral initiation and Xower development (Lona 1968;Perry 1971;García-Luís et al 1992). Compared with annual plants, Xoral transition in perennial plants is initiated in the Wrst growth season, but the development of Xowers is arrested during the winter to ensure production of mature Xowers the next spring compare with annual plants.…”

Cotyledon detachment inhibits development but does not affect precocious flowering of ?Duncan? grapefruit

“…In addition, 'Duncan' seedlings exposed to low temperatures (12 ° C for 4 weeks) under light conditions similar to those of the growth room can flower precociously even though the experiment is done out of the flowering season (data not shown). The importance of cold temperatures had been demonstrated for precocious flowering (Iwamasa & Oba 1973) and for mature flowering (Garcia-Luis et al 1992;Poerwanto & Inoue 1990). Based on our results and the results of the studies cited above, we suggest that the inductive conditions required for mature and precocious flowering are similar.…”