pollen could be a solution for the problem of pollen drift. Materials and Methods Tetraploid development. Two experiments were conducted to produce tetraploid hemp plants by treating pregerminated seeds with colchicine. In Expt. 1, pregerminated seeds of
Abstract
Parsley (Petroselinum crispum L.) seeds osmoconditioned in −1.2 MPa polyethylene glycol 6000 (PEG) for 3 weeks at 15°C emerged earlier and gave higher seedling shoot fresh weights 24 days after planting than raw seeds. Further improvement in earliness of emergence was achieved by fluid-drilling the nongerminated, imbibed seeds in hydroxy ethyl cellulose gel. Germinating the osmoconditioned seeds (42% germination after 4 days at 15° in aerated water) before fluid-drilling decreased the time to 50% emergence by 52% and increased shoot fresh weight by 192% relative to raw seed performance. As emergence rate increased due to treatment, shoot fresh weight increased but emergence synchrony decreased. Neither grading seeds into density classes nor daily PEG replacement during osmoconditioning influenced seedling performance to a practical extent.
Abstract
Pregerminated snapdragon seed was damaged to different extents by low-temperature storage for 4 or 8 days in 3 hydrophilic gels or deionized water. Poststorage viability and vigor decreased as a result of storage, but for apparently different reasons. Medium pH was correlated with poststorage vigor, whereas the gas-exchange capacity of the storage media was correlated with poststorage viability. Seed germination and radicle elongation within the gel was also stimulated when the gas-exchange capacity of the storage medium was increased. Enzymatic generation of oxygen within the gel increased both seed germination and radicle elongation, which suggests that the oxygen diffusion rate specifically was limiting these phenomena.
Abstract
Three glasshouse experiments were conducted in which “starter” N, P, and K fertilizers were incorporated either within or below gel used for fluid sowing pregerminated seed of ‘Avondefiance’ lettuce (Lactuca sativa L.) and ‘Derby Day’ cabbage (Brassica oleracea L. Capitata group). Addition of nutrients to the gel at salt concentrations between 384 and 1893 mg-ion/liter inhibited emergence of the pregerminated seeds. Additions to the gel at concentrations between 9 and 21 mg-ions/liter were too low to affect the growth of the plants. Nutrient solutions applied to the base of the furrow immediately prior to fluid drilling the seeds allowed higher concentrations of salts to be used without reducing emergence. Solutions that contained factorial combinations of 0.84 g/liter N, 1.86 g/liter P, and 2.34 g/liter K applied at the rate of 0.5 ml/cm of furrow increased lettuce dry matter production by up to 44% after 20 days growth, although there was no significant effect on the growth of cabbage. The increase in lettuce growth was mainly in response to P ‘starter’ fertilizer but the largest response was achieved with the N + P + K ‘starter’ treatment.
Abstract
Seed of germinated celery, Apium graveolens L. (Dulce group) and pepper, Capsicum annuum L. were separated from ungerminated seed by density differences in a sucrose and water solution. The top (floating) fraction in both species had the highest percentage germination and percent and rate of emergence compared to either the bottom fraction or unseparated seed.
Abstract
Cabbage seed (Brassica oleracea L. Capitata group cv. Golden Acre) germinated in aerated water went through a pre- and post-radicle emergence separation by specific gravity to separate germinated from nongerminated seed. The desired specific gravity solutions were made with maltrin 250 and water. The percent germinated seed after separation was 99.3; recovery of germinated seed was 95.1%. A metering system was developed to precision plant the germinated seed. Metering rates of 0.5 and 2.0 seed/second were tested in the laboratory and greenhouse. Laboratory tests resulted in 5.7% doubles and 4.9% skips at 2.0 seed/second. Greenhouse test seedling emergence test resulted in 8% doubles and 15.6% skips at the fast rate. Spacing uniformity was acceptable for all tests.
The effect of seed germination rate, or of seedling emergence rate, was studied in relation to subsequent plant growth of `Cortina' lettuce (Lactuca sativa L.). Seedling growth response to selection by time of germination was assessed by imbibing seeds at 5 °C to increase the time range for germination. Germinated seeds were removed daily and transferred to “slants” (germination paper held at 20° from vertical) at 15 °C. Five days after each transfer, root and hypocotyl lengths were measured. As days required for germination increased, root lengths decreased and hypocotyl lengths increased, resulting in no change in total seedling length. The relation between rate of seedling emergence from raw or pelleted seeds of the same lot and shoot fresh weight was examined using commercially practiced hydroponic techniques. Shoot fresh weight at 10 and 21 days after planting was related inversely and linearly to the day of emergence for both seed treatments. In the same study, the coefficient of variation of shoot fresh weight was positively related to time of seedling emergence only at 10 days. Germinated seeds were selected after 1 and 2 days of imbibition; subsequent seedling emergence rate and shoot fresh weight at 25 days were recorded. First-day germinated seeds had faster and more synchronous emergence, and produced heavier and more uniform shoots. Discarding slow-to-germinate seeds should enhance seedling emergence and growth.
Raw, pelleted or germinated seeds of `Cortina' lettuce (Lactuca sativa L.) were sown in phenolic foam cubes preplant soaked in water or fullstrength nutrient solution (2 mmho·cm−1, 2 dS·m−1). The seeds were left uncovered or covered with fine vermiculite (grade 5), and seedling emergence characteristics were subsequently determined. Shoot fresh masses and their coefficients of variation (cv) by 9 days after planting (1 or 2 true leaves) and by 31 days after planting (4 or 5 true leaves) also were determined. Soaking the cubes in nutrient solution rather than water increased seedling emergence percentage and rate, and increased shoot fresh masses by 9 or 31 days after planting. This increased shoot fresh mass was accompanied by lower cv of shoot fresh mass by 9 days after planting, but not by 31 days after planting. Covering seeds with vermiculite decreased emergence from 99% to 93%, but increased shoot fresh mass by 9 and 31 days after planting when cubes were soaked in water, but not in nutrient solution. Seed treatments influenced shoot fresh mass at 9 and 31 days after planting in the order germinated > pelleted > raw. Germinated seeds resulted in lower cv of shoot fresh mass (24%) than raw or pelleted seeds (29%) by 31 days after planting. Thus, sowing germinated seeds into foam cubes soaked in full-strength nutrient solution, with or without covering the seeds with vermiculite, produced the heaviest and most uniform seedlings.
discolored, the stem was sturdy and visibly healthy ( Fig. 5A ), and the root system showed no signs of thinning or root decay ( Fig. 5B ). Fig. 5. The sour orange rootstock plant derived from pregerminated seeds was actively growing at 18 months
Abstract
In the laboratory, gibberellic acid (GA3) applied to Tabasco pepper (Capsicum frutescens L.) seed at 1000 ppm for 48 hr and priming in 2.75% KNO3 for 144 hr significantly stimulated seed germination performance (a function of germination rate and percent germination). In the field, GA3-treated and primed seed treatments were direct-seeded or plug-mix planted and were evaluated for germination, emergence, and yield. In addition, a pregerminated plug-mix seed treatment and a transplanting treatment also were evaluated. Seed priming and GA3 treatment significantly decreased field emergence of both direct-seeded and plug-mix planted treatments. Seedling emergence percentages of untreated seed that was direct-seeded, and pregerminated seed that was planted in plug-mix were significantly higher than other treatments. Greatest stand percentage was observed in the pregerminated seed treatment. Mean rates of emergence increased in primed and pregerminated seed treatments. Total fruit yields of Tabasco were increased by transplanting or pregerminated seed treatments; red fruit yields were greater in pregerminated seed treatments.