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- Author or Editor: Wallace G. Pill x
Matrically priming seeds of common Kentucky bluegrass (Poa pratensis L.) and `SR8300' tall fescue (Festuca arundinacea Schreb.) in fine, exfoliated vermiculite (-1.5 MPa, 20 °C, 4 days) increased subsequent germination rate but did not increase germination percentage or synchrony. The lowest seed: vermiculite ratio (dry weight basis) to provide full priming benefit for seeds of Kentucky bluegrass and tall fescue was 1:10 and 1:20, respectively. Storing Kentucky bluegrass seeds primed in 1:10 (seed:vermiculite) in moist vermiculite for 10 days at either 5 or 20 °C did not reduce germination rate in comparison to primed seeds that were not stored. Primed tall fescue seeds could be stored in moist vermiculite (1:20, seed:vermiculite) for up to 10 days at 5 °C with no loss of priming benefit, but storage for only 2 days at 20 °C resulted in germination. Primed seeds of Kentucky bluegrass (stored for 0 or 10 days at 5 or 20 °C) or tall fescue (stored 0 or 10 days at 5 °C or 2 days at 20 °C) resulted in more rapid germination and seedling emergence, and greater seedling shoot fresh and dry masses than was the case for nonprimed seeds.
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.
The percentage of normal grain amaranth seedlings decreased and that of abnormal seedlings increased as threshing cylinder speed increased from 8.1 to 30.7 m·s-1. At the highest threshing speed, seed deterioration (loss of germination and increase in the percentage of abnormal seedlings) was exacerbated by increasing seed storage from 7 to 47 months. Threshing cylinder speeds of 8.1 to 12.8 m·s-1 resulted in similar percentages of normal seedlings as those achieved with hand-harvesting and threshing. Although injury to hand-harvested seeds or seeds threshed at 8.1 m·s-1 was not apparent, scanning electron micrographs of seeds threshed at 12.8 or 22.4 m·s-1 revealed damage to the seedcoat and the endosperm. Damage extended to the embryo when threshing cylinder speed was increased to 30.7 m·s-1.
Hand-harvested and threshed grain amaranth seeds stored for 6.5 years and combine-harvested and threshed seeds (cylinder speed 26.4 m·s-1) stored for 9.5 years were subjected to several osmotic priming treatment. The selected priming treatment (–1.25 MPa polyethylene glycol at 15C for 10 days) increased percent radicle emergence of hand-harvested seeds and mechanically damaged, combine-harvested seeds and resulted in germination rates that were at least as high as those achieved with other priming treatments. In an incubator test, priming increased percent radicle emergence of hand-harvested seeds only at 15C; however, it increased percent radicle emergence of combine-harvested seeds at 15 and 35C. Priming also increased radicle emergence rate, but this response was more pronounced and exerted over a wider temperature range for the older, lower-vigor, combine-harvested seeds than for the younger, higher-vigor, hand-harvested seeds. In a greenhouse test, hand-harvested seeds had a higher percentage of normal seedlings and a lower percentage of abnormal seedlings than combine-harvested seeds. Priming had no effect on these variables. As a result of priming, normal seedling emergence rate and shoot fresh weight were higher from combine-harvested seeds than from hand-harvested seeds, such that values of these variables for primed, combine-harvested seeds were at least equal to those for nonprimed, hand-harvested seeds. Thus, the invigorating effect of priming was more pronounced for the lower-vigor, mechanically damaged, combine-harvested seeds than for the higher-vigor, hand-harvested seeds.
`Maffei-15' lima beans were subjected to three irrigation regimes (natural rainfall only, partial = 50 mm each week of rain or irrigation from first-flower bud to harvest, and full = 50 mm each week of rain or irrigation from planting to harvest), two between-row spacings (38 and 76 cm), and two in-row plant spacings (5 and 10 cm). The wider in-row spacing increased individual plant vegetative growth but had no effect on economic yield. The combination of 38-cm rows and partial irrigation provided the highest crop growth rate, plant dry matter, leaf area index, water-use efficiency, and economic yieid (equivalent to 3.3 t·ha-1).
One-year-old crowns of `Jersey Giant' asparagus (Asparagus officinalis L.) were forced into spear production at 28C in darkness. Total spear fresh weight and number per square meter responded quadratically to the percentage of sand incorporated in Pro-Mix BX (PMX) peat-lite medium, with maximum yields at 25% to 75% (by volume) PMX. In a second study conducted at 22 and 28C, total spear fresh weight and number per square meter for 96 days of harvest were similar when grown in weathered, spent mushroom compost (SMC) or 1 PMX: 1 sand (v/v), but were lower than those grown in PMX. The lower temperature caused heavier individual spears, while the higher temperature stimulated earlier spear production. During the first month of harvest at 22C, the total number and fresh weight of spears in SMC were 11% and 17% less, respectively, than in PMX. SMC may be a low-cost forcing substrate for white asparagus.
`Moss Curled' parsley [Petroselinum crispum (Mill.) Nyman ex. A.W. Hill] schizocarps were osmotically primed in polyethylene glycol at -1.0 MPa for 7 days at 20 °C. The smaller of the two mericarps within a parsley schizocarp had lower germination percentage, but similar rate and synchrony of germination. Osmotic priming increased germination percentage, rate, and synchrony, irrespective of mericarp half. This promotive effect of priming on germination was associated with embryonic advancement as indicated by a doubling of radicle and cotyledon volumes, without changes in lengths of these organs. Periclinal divisions of the lateral expansion meristem, distinct in primed radicles but indistinct in nonprimed radicles, led to radial alignment of the cortical cells and a doubling of cortical volume and thereby increased radicle volume. Each embryonic cotyledon of primed mericarps had three distinct procambial bundles that differentiated along most of the cotyledon length, while nonprimed cotyledons had from zero to three that differentiated only a short way into the cotyledon. Priming increased coyledonary procambium length by 5-fold and volume by 11-fold. Increased embryonic growth due to priming was associated with greater endosperm depletion adjacent to the embryo. The schizocarps frequently separated or partially separated into component mericarps during priming, indicating a weakening of pericarp tissue along the commissural suture and possibly elsewhere.
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.
'Maffei 15' baby lima bean seeds were sown every 6 cm in rows 76 cm apart to yield a nominal stand of 215,000 plants/ha at two locations in Delaware over 2 years. Seedlings were thinned within 2 weeks of planting to provide 0%, 16.7%, 33.3%, and 50.0% stand reduction at two in-row spacing patterns to determine subsequent effects on vegetative and reproductive growth. Shoot fresh weight per square meter was decreased only in 2003 by 21% and bean fresh weight per square meter was decreased only in 2004 by 13.8% when plant stand decreased to 50%. This disproportional vegetative and reproductive growth response to stand reduction resulted from a compensatory linear increase in shoot fresh weight, usable pod number, and bean fresh weight of individual plants. Thus, 'Maffei 15' lima bean tolerates a considerable loss of plant stand with little or no effect on yield.
A mechanical planter was developed to sow seed of baby lima beans (Phaseolus lunatus) in small plots. The mechanical seeder allowed small plots to be quickly and consistently seeded at a fixed spacing. Seeds were manually spread along a 10-ft (3.0 m) base plate containing 50 holes of slightly larger diameter than the seed length and at the desired seed spacing [2.4 inches (6 cm)]. Once all the holes were filled, a slider plate below the base plate containing holes of the same diameter and spacing, but which were slightly offset, was slid horizontally so that the holes of the base and slider plates aligned and the seeds dropped to the bottom of the furrow. Compared to manual planting, the mechanical planter increased the precision of seed placement and reduced the time needed to plant 50 seeds. The planter was easy to use and transport, and was inexpensive.