Control of Flowering of Xanthium pensylvanicum by Red and Far-red Light

Abstract

Approximately the same energy of red light was required to overcome the inhibitory effect of far-red at the second hour of darkness as was required to produce maximum red light inhibition at the eighth hour. Although far-red light was most inhibitory when given early in a long dark period, approximately the same energy of far-red light was required to saturate the far-red response at the fourth, eighth and sixteenth hours.The results are discussed in relation to other reports of far-red inhibition of flowering in short-day plants.It seems clear that the pigment phytochrome is involved somehow in the photoperiodic response.

A role of phytochrome in photoperiodic induction: Two‐phytochrome‐pool theory

“…(1) The time of effectiveness of red and far-red irradiations A brief exposure to R given at the 6-12 h and 22-36 h of a long dark period (48, 64 or 72 h) inhibits flowering, but that given at the 16-24 h has little effect in Pharbitis (Takimoto and Hamner 1965a). Similar rhythmic responses to R have been reported for Hyoscyamus (Claes and Lang 1947), Kalanchoe (Carr 1952), Glycine (Coulter and Hamner 1964), Chenopodium (Cumming et al 1965) and Xanthittm (Reid et al 1967). Probably, the action of R is controlled by an endogenous rhythm.…”

Night Break Treatment Using Different Light Sources Promotes or Delays Growth and Flowering of Eustoma grandiflorum (Raf.) Shinn.

“…Conforming to the principle of the phytochrome theory, red light was most effective for retardation of flowering in most short-day plants such as Pharbitis nil Choisy (Takimoto and Hammer, 1965) and Xanthium pennsylvanicum Wallr. (Reid et al, 1967). On the other hand, flowering in the long-day plant Hordeum vulgare L. was enhanced by adding far-red light to the main light portion of the photoperiod, and the flowering response was correlated to the R (656-664 nm): FR (726-734 nm) ratio (Deitzer et al, 1979).…”

The Participation of Two Rhythms in the Leaf Movements of Xanthium Plants Given Various Light-Dark Cycles

“…The cultural conditions and methods were similar to those used by previous investigators in this laboratory (13). The growth chambers used have power groove fluorescent lamps, which give 7500 lux at the leaf surface.…”