Oat development in response to temperature

ABSTRACT: Temperature affects plant development therefore phyllochron has been used as a predictor for developmental events to define the time for agricultural managing practices. This study aims to evaluate changes in phyllochron and thermal sum required for flowering by oat genotypes developed at different decades at three temperature regimes; the effect of high temperature on phytomere development; and identify the development stage at the moment of meristem transition to reproductive stage. Three environments were obtained by sowing in the fall, in the spring, and under constant temperature (17oC), always at inductive photoperiod. Despite changes in nominal values small differences were found among genotypes’ phyllochron. Adding specific optimal and maximum temperatures into the growing degree days’ calculation demonstrated phyllochron stability among environments. Plant cycle length and thermal sum correlated with the number of developed phytomeres. UFRGS 078030-2 plants flowered earlier, had a small number of phytomeres, and greater tolerance to elevated temperatures than the other genotypes. More recent genotypes transit to reproductive stage at an earlier Haun stage than older ones.

The effect of inductive photoperiod on flower formation and phytohormones level in a long day plant Hyoscyamus niger L.

The anatomical and hormonal investigations on a long day plant <i>Hyoscyamus niger</i> L. during the time of the generative photoinduction have been conducted. The plants were grown during 75 days on a short photoperiod and then they were transferred to long day conditions. The earliest anatomical symptoms of flower initiation were noticed after four long photoperiods. The inductive photoperiod causes also a general increase in the amounts of phytohormones. During the flower evocation the intensive accumulation of cytokinins and gibberellins in leaves takes place. The post-inductive period, in which the development of flower elements happens, is characterized by changing amount of phytohormones. The content of hormonal substances is subjected to the rhytmical changes related to the periods of light and darknees in the twenty four hours' cycle.

Effects of Night-Interrupted Lighting on Growth and Flowering Duration of Herbaceous Perennials Grown Under Nursery Conditions in the Southern United States

Staggered starting dates for night-interrupted lighting (NIL) were evaluated for accelerated sequential flowering of herbaceous perennials with different photoperiod requirements outdoors in a southern nursery setting. Plants evaluated were black-eyed Susan (Rudbeckia fulgida ‘Goldsturm’), an obligate long-day (LD) plant; obedient plant (Physostegia virginiana ‘Miss Manners’), a facultative LD plant; and Stokes' aster (Stokesia laevis ‘Peachie's Pick’), a facultative intermediate-day plant. With all species, the dates of first flower and maximum flower number occurred sooner under LDs from incandescent (INC) and fluorescent (FLU) lamps than under natural photoperiod (NP). Mean and maximum flower numbers were greater under NIL than under NP for black-eyed Susan and Stokes' aster but not for obedient plant. Time in flower increased in Stokes' aster, but either decreased or was not affected by NIL for black-eyed Susan and obedient plant. Flowering periods of black-eyed Susan and obedient plant exposed to different NIL timings overlapped extensively while leaving a gap in flowering between plants exposed to NIL and those under NP. This gap in flowering suggests that the intervals between NIL start dates could be longer to lessen the flowering overlap of plants under NIL, and that the interval between the start of the last NIL treatment and the onset of an inductive photoperiod be reduced to maintain sequential peak flowering until the natural flowering period. With Stokes' aster, flowering overlapped for plants in the different NIL timings and under NP, resulting in continuous sequential blooms from first flowering of plants under NIL until the plants' natural flowering period under NP in late May. Flowering periods of Stokes' aster exposed to NIL beginning on different dates overlapped extensively, suggesting that at least one NIL start date could be omitted and the intervals between the start of NIL increased without sacrificing continuous sequential peak flowering. NIL from INC and FLU lamps promoted growth in plant height compared to that of plants under NP, although the increase in plant height was less under FLU lamps.

The effect of photoperiodic treatments on mitotic activity in Pharbitic nil Chois

The short-day plant, <i>Pharbitis nil</i>, requires only a single inductive cycle with a 16-hour dark period for flowering. The mitotic activity in the shoot apices was studied directly after the termination of the inductive photoperiod. A pronounced rise in the mitotic index was found in the 2nd and the 8th-14th hours. Control plants grown under noninductive conditions (continuous light, a light interruption in the middle of the dark period) did not flower and did not show an increased mitotic index. The increased mitotic activity in the shoot apices of <i>Pharbitis</i> seems to be causally connected with the phytochrome-controlled entry of the plants into the state of generative induction.

Influence of night-breaks on flowering and phytohormones content in Hyoscyamus niger L.

Night-breaks caused both stimulated shoot growth and caused formation of flowers as well as a general increase in the content of phytohormones in leaves of the long-day plant <em>Hyoscyamus niger</em> L. At the time of flower formation in night-break treated plants, new gibberellin-like substances also appear. The results show that night-breaks cause similar changes in the phytohormones content as a long inductive photoperiod. It may be assumed that independently of the way of induction, the generative differentiation of long-day plants is always accompanied by a general increase in the amount of endogenous hormones and the appearance of new gibberellins. These results suggest the possibility of a morphogenetic role of hormones, especially gibberellins, in the phenomena of flower formation and differentiation.

Phytohormones level in the leaves of Hyoscyamus niger L. during variable photoperiods at the time of flower initiation and differentiation

The investigations concern changes in the content of endogenous phytohormones in the leaves of the long-day plant <em>Hyoscyamus niger</em> L. during variable photoperiods applied before and after flower initiation. The results show that alternation of inductive photoperiods with short days leads to quantitative changes in the content of phytohormones. The changeable photoperiod leads to a general decrease in the contents of gibberellins, cytokinins and auxins during the short noninductive days both before and after flower initiation. Alternation of the inductive photoperiod with short days does not influence the content of abscisic acid-like substances before flower initiation and causes an increase of the amount of inhibitors in the postinductive period. The content of hormonal substances is subjected to rhytmical changes related to the periods of light and darkness in the twenty-four hours' cycle.

Limited Inductive Photoperiod Affects Herbaceous Perennials Grown Under Nursery Conditions in the Southern United States

A study was conducted to determine if limited inductive photoperiod (LIP) initiated in late winter could be used to control stem elongation in ‘Goldsturm’ coneflower (Rudbeckia fulgida ‘Goldsturm’), ‘Moonbeam’ coreopsis (Coreopsis verticillata ‘Moonbeam’), or ‘Early Sunrise’ coreopsis (Coreopsis grandiflora ‘Early Sunrise’), grown outdoors under nursery conditions in the southern United States, without negating the benefits of earlier flowering from night-interrupted lighting (NIL). Treatments were NIL beginning on February 1 and ending on February 15, March 1, March 15, or April 1,2002, plus a natural photoperiod (NP) treatment. The experiment was repeated in 2003 with the inclusion of an additional NIL treatment ending on April 15. LIPs of at least 15 to 30 days, 30 to 45 days, and 30 to 45 days promoted earlier flowering of ‘Early Sunrise’ coreopsis, ‘Moonbeam’ coreopsis, and ‘Goldsturm’ coneflower, respectively. Flower counts and quality ratings of the three cultivars that received LIPs were similar to or higher than those of plants under a NP, except for a reduction in flowering and quality ratings of ‘Goldsturm’ coneflower exposed to LIPs ending on March 1 and March 15, 2002, and on March 1, 2003, and later. LIP effects on plant height were mixed, although there was at least one duration of LIP that resulted in earlier flowering of the three cultivars and plants similar to or shorter than plants under a NP.

Activities of antioxidative enzymes during Chenopodium rubrum L. Ontogenesis in vitro

For the short-day plant Chenopodium rubrum, a 14 h/10 h photoperiod is inductive for flowering, while continuous light (CL) is noninductive. Plants of one group were grown continuously under an inductive photoperiod, while in the other group flowering induction was delayed by 17 days of CL in order to separate on the time scale different developmental phases in plants of the same age. Regardless of the photoperiodic conditions the plants were exposed to, seed maturation occurred in 10 weeks. Activities of catalase (CAT), superoxide dismutase (SOD), and peroxidase (POD) were determined in different phases of development (vegetative growth, flowering, seed development, and maturation). The activities of antioxidative enzymes depended on both the phase of development and the photoperiod. In plants grown continuously under an inductive photoperiod, high CAT and POD activities were detected at the time of flowering and decreased during seed development and maturation. In plants in which flowering induction was delayed by 17 days of CL, the activities of POD and SOD were lowest in the vegetative phase of development and attained maximum values in the phase of seed maturation. In both groups of plants, the highest CAT activity was measured at the time of flowering.