Abstract
The main theme of the submission is the role of seed source and
sowing/planting method on the establishment of vegetable crops and
on the uniformity of time of maturity and weight of individual
plants. It is also concerned with the effect of the environment
during seed production on seed quality, with the manipulation of
husbandry practices during the production of seeds and during the
establishment of the crop, to improve the efficiency of crop
production.
Work on potatoes showed how the yields of small tubers for
canning whole could be increased and the season of supply extended
by using particular combinations of sizes of seed tubers and seed
rates to manipulate stem densities. This, the identification of a
suitable cultivar and the use of a 'mini-bed' system of production
were widely adopted by the industry. The number of tubers and
their growth were also shown to be influenced by the method of
growing and storing the seed tubers, by water supply and by
changes in the supply of assimilates at the time of tuber
initiation.
Work on small-seeded vegetables demonstrated the relationship
between variation in plant size in the subsequent crop with the
methods of culture and other factors during the production of the
seed. These cultural practices and the position of the seed on
the plant were found to be significant sources of variation in
quality between seed lots. Parallel cytological studies showed
that the responses to seed-crop cultural practices were related to
differences in the size of the embryo rather than that of the
seed. The quality of the seed was also affected by temperature /
during its development and by the drying conditions during
maturation and after harvest. The volume of the ovule and
embryo-sac at fertilisation and the number of endosperm cells were
shown to regulate seed size in carrot.
To enable growers to exercise greater control over the
germination and emergence phases of growth, a technique of sowing
pre-germinated seeds was developed. This system gave earlier,
higher and sometimes more uniforn emergence and crop maturity than
traditional systems using dry, 'advanced' or 'primed' seeds. In
lettuce, high-temperature induced dormancy was identified as a
major factor influencing establishment, seeds being sensitive at
two stages during the germination process. Sowing pre-germinated
seeds with a fluid drill overcame this dormancy in lettuce and
also the effects of low temperature which delay and reduce the
germination and emergence of tomato and Umbelliferous crop seeds.
Studies of the effects of the number of seeds germinated at the
time of sowing, radicle length, amount of gel carrier and the
environment after sowing on the responses to fluid drilling
enabled the components of the system to be optimised.
