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
PNL Volume 16 1984
1. Berry, G. J. and Y. Aitken. 1979. Aust. J. Plant Physiol. 6:573-
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.