Joyce R. A. Steckel

Drought tolerance in potatoes

In field experiments made over 3 years Pentland Crown and Majestic gave, in general, higher total and dry matter yields from plots given no supplementary water and protected from rainfall throughout growth than King Edward or Maris Piper. However, on plots kept at or near to field capacity all varieties gave similar yields. Pentland Crown and Majestic were deeper rooting than the other two varieties at the time of tuber formation (when the production of new roots ceased) but the differences in rooting depth ( ca. 100 mm) between the varieties were small. Except for the top 150 mm of soil, differences in water extraction between the varieties throughout the profile were also small. Neither these differences in water extraction nor the differences in rooting depth could be related consistently to the differences in varietal yield response between ‘wet’ and ‘dry’ plots.

Some effects of umbel order and harvest date on carrot seed variability and seedling performance

SummaryThere were no effects of umbel order or date of seed harvest on the coefficient of variation (CV) of carrot seed weight. Seed grading reduced the CV from 31% to 22% compared with ungraded seeds and the effects were similar for all treatments. The CV of embryo length was lower in seeds from primary (P) than secondary (S) umbels and it declined with a delay in harvest, the reduction being greater for seeds from S umbels. Seed grading had no effect on the CV of the embryo length of ऩ seeds but it reduced the CV of S seeds, particularly at the early harvest. Fewer seedlings emerged and emergence was later from early-harvested and S umbel seeds than from late-harvested’ and ऩ umbel seeds, and the last two sources also produced larger seedlings than the first two, even after allowing for differences in seed weight. The CV of seedling weight decreased with a delay in harvest and was lower from seeds from ऩ than from S umbels, particularly at the early harvest. In general, grading improved the emergence ch...

Seed quality in carrots: the effects of seed crop plant density, harvest date and seed grading on seed and seedling variability

SummaryCarrot seeds (Chantenay types) harvested 44–61 days after anthesis (early harvest) had higher coefficients of variation (CVs) of embryo length and subsequent seedling weight than those of seeds harvested 70–92 days after anthesis (late harvest). Seed grading after harvesting the seed crop reduced the CVs of some of the early harvested seed crops. Seed crops grown at high plant density (80 plants m—2) compared with low density (10 plants m-2) produced seed with lower CVs but the effects were small. Averaged over three experiments the CVs of seedling weight from early- and late-harvested seeds were 53% and 43%, respectively. For high- and low-density crops the corresponding figures were 49% and 47% and for ungraded and graded seeds 50% and 45%. The CV of seedling weight and the ‘spread’ of seedling emergence times were closely related to the CV of embryo length but not to the CV of seed weight. This suggests that, in addition to estimates of viability determined by standard tests, a measurement of th...

Studies on carrot seed production: effects of plant density on yield and components of yield

SummaryThe yield of carrot seed (Chantenay types) increased by about 50%-55% with an increase in plant density from 10 to 80’plants m-2 in two experiments but in another there was no effect of density. The percentage of the yield contributed by the primary umbel was, on average, 25% and 62% for the low and high density crops, respectively. Increasing the plant density from 10 to 80 plants m-2 reduced the number of seeds per plant, largely because of fewer umbels, per plant. At anthesis, or soon after, seeds from primary umbels and low-density crops “were heavier, than those from secondary umbels and high-density crops. These differences were maintained throughout growth and, in . one year, were intensified by the shorter period of seed growth in the high-density crop. The lower mean seed weight in 1979 compared with 1980 was associated with a shorter period of seed growth and higher temperature after anthesis.

The effects of fluid sowing pre-germinated seeds and transplanting on emergence, growth and yield of outdoor bush tomatoes

Experiments on outdoor bush tomatoes cv. Sleaford Abundance were conducted during 3 years to compare seedling establishment from fluid-sown pre-germinated seeds with that from conventionally sown dry seeds and to compare the effects on ripening and yields of these establishment methods with transplanting. Fluid-sown pre-germinated seeds emerged about 15 days earlier than conventionally sown dry seeds from sowings made in late April (mean soil temperature at seed depth from sowing to emergence ranged from 9 to 11.5 °C) and about 6 days earlier from sowings made in mid-May (mean soil temperature ranged from 12 to 15 °C). The percentage seedling emergence from pregerminated fluid-sown seeds was, on average, 57% from the earlier sowings and 65% from the later sowings, 34 and 24% higher, respectively, than from dry seeds sown conventionally. Plants from fluid-sown pre-germinated seeds were about 50% heavier than those from dry seeds at all stages of growth up to flowering. Crops established by fluidsowing started to ripen 7 days earlier than those established from dry seeds, when averaged over sowing dates and years. Yields of ripe marketable fruit > 35 mm in. size from crops established from pre-germinated seeds were 35·2 t/ha, averaged over sowing and planting dates, 37% higher than from dry seeds though 51% lower than from transplants. In the two years with good growing seasons crops fluid sown in late April gave as good yields as those transplanted in late May and early June, after the last frosts, though in the cool wet year yields from fluid-sown crops were considerably lower than those from transplanted crops. Yields of ripe, marketable fruit from ‘bare-root’ plants raised from pre-germinated seeds in unheated Dutch-light structures were, on average, 48·5 t/ha, 25% higher than from plants raised in soil blocks in a heated glasshouse.

The effects of seed-crop plant density, transplant size, harvest date and seed grading on leek (Allium porrum L.) seed quality

SummaryIn three years’ experiments the percentage seedling emergence from seed compost in glasshouse tests was between 83% and 91%, when averaged over all treatments. Crops grown at 97 plants m−2 produced seed of higher viability and, for 1983- and 1984-seed 6% to 7% higher percentage seedling emergence in the field than seed from crops grown at 11 plants m−2. There were no effects of steckling transplant size or variability on the subsequent performance of the seed. Seed-crop harvest date, over the range from c. 45–90 days after flowering, had little effect on percentage seed germination and seedling emergence except in 1982 where early harvesting reduced seedling emergence in the field. There were no consistent or large effects of seed-crop harvest date on the coefficient of variation (CV) of seed, seedling or mature plant weight. Large seed (2. 00–2.24 mm) increased seedling emergence in the field by 13% compared with ungraded seed and by 21% compared with the smallest size grade (1.60–1.80 mm). Seed g...

Priming and pre-germination of parsnip (Pastinaca sativa L.) seed

SummarySeedling emergence and growth responses to priming seeds in polyethylene glycol solutions, to germinating them before sowing and to a combined priming and pre-germination treatment were examined in the field and growth rooms using several stocks of seed. Priming or priming and pre-germinating seeds of a slowly germinating stock improved the percentage seedling emergence compared with untreated and pre-germinated seeds. In rapidly germinating stocks all three seed treatments showed similar levels of emergence which were higher than those of untreated seeds. Both priming and pre-germinating seeds reduced the mean emergence time and, in general, the effect of the combined treatment was greater than either treatment alone. Priming alone generally had no effect on the spread of emergence time or on seedling or plant weight variability, but pre-germinating seeds increased variability, particularly in a slowly germinating stock. Priming seeds before pre-germinating them reduced this variability.

The effects of pre-sowing seed treatments on the germination and emergence of lettuce seeds at high salt concentrations

Abstract Radicle emergence in lettuce seeds cultivar ‘Hilde’ was reduced by NH4NO3 above 8×10−2M, while radicle extension was inhibited by 8×10−2M NH4NO3 and no seedlings emerged. Inhibition of radicle emergence by 8 and 16×10−2M NH4NO3 was prevented by soaking seeds for 4 h before sowing in a mixture of GA 4 7 and kinetin+phosphate buffer, and was partially prevented by soaking them for 4 h before sowing in phosphate buffer. These treatments did not prevent inhibition of radicle emergence by 32×10−2M NH4NO3, but seeds soaked in growth regulators or phosphate buffer before sowing and taken from this NH4NO3 solution after 7 days and washed to remove excess salt gave 45–52% germination compared with 12 % for untreated seeds. Pre-treatment of the seeds did not prevent the inhibitory effect of NH4NO3 on radicle extension. In field experiments seeds treated with growth regulators + phosphate buffer or phosphate buffer alone gave a higher final percentage emergence from soils given 125 kg N/ha than did untreated seeds.

Improving seedling establishment by a dibber drill

SummaryEight experiments with onion, three with leek and three with lettuce over the period 1991–1993 examined the influence of dibber and coulter drills on seedling establishment. In some of the experiments Alcosorb was applied to cover the seeds in the dibbed holes and Soiltex was applied as a band to the soil above the line of seeds. Additionally, seeds of differing quality and primed seeds were used. The dibber drill gave more uniform depth of sowing and spacing between seed positions than the coulter drills and it improved seedling emergence, substantially, where a soil cap or crust formed after sowing, and sometimes gave earlier and more uniform seedling emergence. It appeared that part of the improvement could be ascribed to better water supply to the seed associated with compaction of the soil around the seed and, indeed, there were benefits from using a seed press wheel sited immediately behind the point of seed delivery with the coulter drill. The use of Soiltex reduced impedance to shoot growth...

Effects of Pre-Sowing Treatments of Seeds on the Germination and Establishment of Parsnips

SummarySowing parsnip seeds ‘primed’ in salts (KNO3+K3PO4Hc2O) or polyethylene glycol solutions gave, on average, 1.8 days earlier seedling emergence than from untreated seeds. Sowing seeds subjected to different numbers and lengths of cycles of wetting and drying (‘hardening’) advanced seedling emergence by a similar amount. However, the earlier emergence from these seed treatments was small compared with that obtained by fluid-sowing pre-germinated seeds which advanced emergence by c. 4-0 days. Sowing pre-germinated seeds also increased the final percentage emergence by c. 60% compared with untreated, hardened and primed seeds, and at an early sowing reduced the spread of emergence.