Germination and Early Seedling Growth of Chaffy-Seeded Grasses at Negative Water Potentials

نویسنده

  • T. L. Springer
چکیده

chaffy-seeded grasses can be debearded, i.e., removal of the hairs and awn (Ahring et al., 1964) or processed to Drought is the most frequent cause of stand establishment failure remove all appendages leaving only caryopses (Beisel, of native grasses. An experiment was conducted to determine the interactions of seed processing and simulated dry conditions on seed 1985). When conditions are favorable, planting caryopgermination and seedling growth of five chaffy-seeded, warm-season ses offer lower seeding rates and more uniform seedling grasses. Seed of big bluestem (Andropogon gerardii Vitman), sand emergence, but during unfavorable conditions caryopbluestem (Andropogon hallii Hack.), little bluestem [Schizachyrium ses are more susceptible to attack from microorganisms scoparium (Michx.) Nash], yellow bluestem [Bothriochloa ischae(Rollins and Ahring, 1987). Chaffy seed tend to have mum (L.) Keng. var. ischaemum (Hack.) Celarier and Harlan], and greater seed dormancy than more heavily processed indiangrass [Sorghastrum nutans (L.) Nash] were processed into inseed, allowing for earlier planting in less favorable contact spikelets-chaffy pure-seeds, debearded spikelets-chaffy pureditions (Springer, 1991). seeds lightly trimmed of hair and awns, and caryopses. Fifty-seed Several experiments have simulated the effects of samples of each species and seed form were germinated at water moisture stress on seed germination and growth of potentials of –1.6, –0.8, –0.4 ,–0.2, and 0 MPa for a 21-d period. There were species water potential and species seed form interactions plants (Helmerick and Pfeifer, 1954; McGinnies, 1960; for 7-d germination, 21-d germination, and potential maximum germiParmar and Moore, 1968; Knipe, 1973; Sharma, 1973, nation, and for seedling root and shoot lengths. In general, seed germina1976). These studies used a number of chemical comtion and seedling growth were reduced as the water deficit potentials pounds to simulate water deficits, such as, carbowax 6000, increased. Germination was slower and much lower from intact and d-mannitol, glucose, NaCl, sucrose, polyethylene glycol debearded spikelets compared with caryopses. The slower germination (PEG), and polyvinylpyrrollidone. The most commonly of intact and debearded spikelets also resulted in shorter root and shoot used compounds were mannitol and polyethylene glylengths when compared with caryopses. Given the amount of genetic col because they are considered chemically inert and variation within most cross-pollinated species, this procedure could be nontoxic to plant growth (Parmar and Moore, 1968; used as an effective selection tool for breeding cultivars with improved Bell, 1974). germination and seedling growth at low water potentials. The interactions of seed processing with plant species, germination under moisture stress, and early seedling growth are not well defined. Seed processing affects the S factors influence seed germination, early rate of germination of chaffy-seeded grasses (Ahring seedling growth, and associated stand establishment et al., 1964; Springer, 1991). Similarly, moisture stress of warm-season pasture grasses. Such factors include indecreases seed germination and seedling growth (Helmadequate seed-bed preparation, improper seeding depth, erick and Pfeifer, 1954; Wiggins and Gardner, 1959; late seeding date, inferior seed quality, competition from Parmar and Moore, 1968). Thus, the objective of this exweeds, crusting of soil surface, and drought. Of these, periment was to determine the interactions of seed prodrought is undoubtedly the most frequent cause of plant cessing and moisture stress on the germination and seedestablishment failure (Blake, 1935). ling growth of five chaffy-seeded, warm-season grasses. The inherent nature of the seeding unit can also cause difficulty in the proper placement of seed. The term “chaffy-seed” denotes seed units consisting of a caryopMATERIALS AND METHODS sis and its subtending appendages (lemma, palea, glumes, The chaffy-grass seed used for study were representative hairs, and awns). Chaffy grass seed are inherently more of plant materials available to producers. Chaffy seed of difficult to store and to plant than non-chaffy seed. Re‘Rountree’ big bluestem, ‘Osage’ indiangrass, and ‘Aldous’ moval of the chaffy appendages eases planting difficullittle bluestem were purchased from commercial sources. ties but can limit the longevity of seeds in storage even Chaffy seed of ‘WW-Spar’ yellow bluestem, and ‘Chet’ sand under the best of conditions (Ahring, 1962). Seed of bluestem were produced at the USDA, ARS, Southern Plains Range Research Station, Woodward, OK. The chaffy seed of each grass species was blown with the USDA-ARS, Southern Plains Range Res. Stn., 2000 18th Street, Woodaid of a Seedburo seed blower (Seedburo, Chicago, IL) at air ward, OK 73801. Mention of a trademark or a proprietary product valve openings of 30, 27, 30, and 22 mm for indiangrass, little does not constitute a guarantee or warranty of the product by USDA. bluestem, big and sand bluestem, and yellow bluestem, respecAll programs and services of the USDA are offered on a nondiscriminatory basis without regard to race, color, national origin, religion, tively. Each seed lot was blown in 3-g increments to remove sex, age, marital status, or handicap. Received 20 Jan. 2005. *Correall light and empty chaffy seed units. The chaffy pure-seed sponding author ([email protected]). (consisting of a caryopsis and its subtending appendages) content of the heavy seed fraction of this blowing technique was Published in Crop Sci. 45:2075–2080 (2005). 98% ( 1%) for each species. Thirty grams pure seed of each Forage and Grazing Lands species was obtained in this manner and assigned to one of doi:10.2135/cropsci2005.0061 the following treatments: (i) intact spikelets–chaffy pure-seeds, © Crop Science Society of America 677 S. Segoe Rd., Madison, WI 53711 USA (ii) debearded spikelets–rough pure-seeds lightly trimmed of 2075 Published online August 26, 2005

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تاریخ انتشار 2005