THE FLOWERING BEHAVIOR OF LINE R142F

54 PNL Volume 16 1984 RESEARCH REPORTS

Murfet, I. C. Botany Department, University of Tasmania

Hobart, Tasmania 7001, Australia

Gottschalk (2) reported that under the phytotron conditions at

Bonn his line R142F flowered at node 39 (counting frora the first scale

leaf as node 1) in continuous light, while the plants did not flower in

a short-day photoperiod of 12 h (temperature - day 25°C, night 15°C).

These results exceed the bounds of behavior previously reported for

peas, suggesting the presence of a novel genotype for R142F. It was of

interest, therefore, to examine the behavior of R142F under the

phytotron conditions at Hobart, where a considerable diversity of

material has been tested in recent years (8, 10). Only five plants were

grown but the results are unequivocal. The three plants in continuous

light flowered at node 22 and the two plants in 8 h short-day conditions

flowered at nodes 64 and 76. These results for R142F place It in the

phenotypic class variously known as G (3) or LHR (5). The large

response to photoperiod is characteristic of lines with the gene com-

bination Sn Dne Hr (7, 10), and the high flowering node in continuous

light is characteristic of lines with gene Lf (9). The Hobart results

for R142F are entirely consistent with those previously obtained for

lines known to possess genotype Lf Sn Dne Hr, e.g. L16 (5, 6).

The flowering behavior of line R142F may therefore be accounted for

in terms of presently identified genes. However, an explanation of the

discrepancy between the Bonn and Hobart results is called for. The

explanation is not likely to involve temperature, since fairly similar

conditions were used in both cases. The night temperature used at

Hobart, 17c, was slightly higher, but if anything these conditions

would be somewhat less conducive to flowering (1). The 17-node dif-

ference in flower initiation under continuous light at the two sites is

very substantial, since this character shows a low variance under these

conditions. The explanation probably involves a difference in the light

supply. Light intensity has little effect on flowering within the

normal operating range, but light quality may have a considerable effect

(7). A differential response to fluorescent and incandescent light by G

= LHR lines is well established (4, 11). The 24 h photoperiod used at

Hobart consists of natural light extended by light from a mixed

incandescent/fluorescent source (100W tungsten filament Incandescent

globes and Thorn 40 W white fluorescent tubers arranged alternately in a

linear array) providing approximately 10 Wm at the top of the pots.

It would appear the light source used at Bonn is not fully effective in

satisfying the photoperiod requirement imposed by the Sn Dne Hr system.

The reason for the failure of R142F to flower In a 12 h photoperiod

at Bonn is not clear. It has been our experience that most LHR plants

will eventually flower in short days if they can be kept growing in a

healthy state, although the process may take over a year (7). In the

present case the latest R142F plant took 165 days to flower. Active

growth of the main shoot was encouraged by regular excision of lateral

branches.

PNL Volume 16 1984

RESEARCH REPORTS

1. Berry, G. J. and Y. Aitken. 1979. Aust. J. Plant Physiol. 6:573-

587.

2. Gottschalk, W. 1983. PNL 15:24-25.

3. Marx, G. A. 1968. Bioscience 18:505-506.

4. Marx, G. A. 1969. Crop Sci. 9:273-276.

5. Murfet, 1. C. 1971. Heredity 26:243-257.

6. Murfet, I. C. 1975. Heredity 35:85-98.

7. Murfet, I. C. 1977. In_: The Physiology of the Garden Pea, eds.

J. F. Sutcliffe and J. S. Pate. Academic Press, pp. 385-430.

8. Murfet, I. C. i978- PNL 10:48-52.

9. Murfet, 1. C. 1981. PNL 13:40-41.

10. Murfet, I. C. 1984. In: Handbook of Flowering, ed. A. H. Halevy.

CRC Press, Vol. IV (in press).

11. Reid, J. B. 1982. Crop Sci. 22:266-268.



	54 PNL Volume 16 1984 RESEARCH REPORTS

	THE FLOWERING BEHAVIOR OF LINE R142F Murfet, I. C. Botany Department, University of Tasmania Hobart, Tasmania 7001, Australia Gottschalk (2) reported that under the phytotron conditions at Bonn his line R142F flowered at node 39 (counting frora the first scale leaf as node 1) in continuous light, while the plants did not flower in a short-day photoperiod of 12 h (temperature - day 25°C, night 15°C). These results exceed the bounds of behavior previously reported for peas, suggesting the presence of a novel genotype for R142F. It was of interest, therefore, to examine the behavior of R142F under the phytotron conditions at Hobart, where a considerable diversity of material has been tested in recent years (8, 10). Only five plants were grown but the results are unequivocal. The three plants in continuous light flowered at node 22 and the two plants in 8 h short-day conditions flowered at nodes 64 and 76. These results for R142F place It in the phenotypic class variously known as G (3) or LHR (5). The large response to photoperiod is characteristic of lines with the gene com- bination Sn Dne Hr (7, 10), and the high flowering node in continuous light is characteristic of lines with gene Lf (9). The Hobart results for R142F are entirely consistent with those previously obtained for lines known to possess genotype Lf Sn Dne Hr, e.g. L16 (5, 6). The flowering behavior of line R142F may therefore be accounted for in terms of presently identified genes. However, an explanation of the discrepancy between the Bonn and Hobart results is called for. The explanation is not likely to involve temperature, since fairly similar conditions were used in both cases. The night temperature used at Hobart, 17c, was slightly higher, but if anything these conditions would be somewhat less conducive to flowering (1). The 17-node dif- ference in flower initiation under continuous light at the two sites is very substantial, since this character shows a low variance under these conditions. The explanation probably involves a difference in the light supply. Light intensity has little effect on flowering within the normal operating range, but light quality may have a considerable effect (7). A differential response to fluorescent and incandescent light by G = LHR lines is well established (4, 11). The 24 h photoperiod used at Hobart consists of natural light extended by light from a mixed incandescent/fluorescent source (100W tungsten filament Incandescent globes and Thorn 40 W white fluorescent tubers arranged alternately in a linear array) providing approximately 10 Wm at the top of the pots. It would appear the light source used at Bonn is not fully effective in satisfying the photoperiod requirement imposed by the Sn Dne Hr system. The reason for the failure of R142F to flower In a 12 h photoperiod at Bonn is not clear. It has been our experience that most LHR plants will eventually flower in short days if they can be kept growing in a healthy state, although the process may take over a year (7). In the present case the latest R142F plant took 165 days to flower. Active growth of the main shoot was encouraged by regular excision of lateral branches.