Jw. Warringa et al., THE PATTERN OF FLOWERING, SEED SET, SEED GROWTH AND RIPENING ALONG THE EAR OF LOLIUM-PERENNE, Australian journal of plant physiology, 25(2), 1998, pp. 213-223
A greenhouse pot experiment was conducted to elucidate the pattern of
decreasing seed set and seed dry weight found from the basal to the up
per spikelet in Lolium perenne L. ears and-very markedly-acropetally w
ithin a spikelet. The changes in fresh and dry weight of the seed afte
r anthesis were monitored for 12 positions within the ear. To determin
e the duration of seed growth, the spatial and temporal patterns of fl
owering and ripening along the ear were assessed. The proximal florets
of the central spikelets flowered first, and the upper spikelets in t
he ear flowered before the basal spikelets, with flowering proceeding
acropetally within a spikelet. The upper spikelets ripened earlier tha
n the basal ones, and the seeds within a spikelet ripened simultaneous
ly. These patterns of flowering and ripening along the ear resulted in
different durations of seed growth along the ear. Thus from the proxi
mal to the distal seed within a spikelet the duration of growth decrea
sed by 26%, the rate of growth fell by 48% and seed set and seed dry w
eight also fell sharply. Of the total variation in maximum, final seed
dry weight within the ear, 4% could be attributed to the difference i
n seed dry weight between spikelets and 89% to differences in seed dry
weight within spikelets. Differences in duration and rate of seed gro
wth and seed set were also much smaller between spikelets than within
spikelets. About 60% of the differences in seed dry weight along the e
ar were attributable to differences in growth rate and about 30% to di
fferences in the duration of seed growth. The relative growth rate did
not differ between seeds in different positions. The main factor dete
rmining seed growth rate was the dry weight of the ovule at anthesis,
which declined sharply from the proximal to the distal floret within a
spikelet. Analysis of the fructose, glucose, sucrose and starch conce
ntrations showed that seed growth was not limited by the availability
of sucrose nor by the ability of the seeds to convert sucrose into sta
rch. These conclusions were supported by results from a second greenho
use experiment in which all ovules in 50% of the spikelets were remove
d at anthesis. Dry weight of the remaining seeds increased by only 15%
.