Switchgrass (Panicum virgatum L.)—a perennial, warm-season (C4) species—evolved across North America into multiple, divergent populations. The resulting natural variation within the species presents considerable morphological diversity and a wide range of adaptation. The species was adopted as a crop—initially as a forage—only in the last 50 yr. Its potential uses have recently been expanded to include biofuels. Management of switchgrass for biofuels is informed by an understanding of the plant's biology. Successful establishment requires attention to seed dormancy and weed control as well as proper depth and date of planting. The plant's growth rate is closely tied to temperature, but timing of reproductive development is linked to photoperiod. Accordingly, the period of vegetative growth can be extended by planting lower-latitude cultivars at higher latitudes. This strategy may provide a yield advantage, but cold tolerance can become limiting. Switchgrass is thrifty in its use of applied N; it appears a...

The Biology and Agronomy of Switchgrass for Biofuels

Seed germination and seedling growth, survivorship, and final biomass and their responses to watering interval were studied in two grass and six forb species to assess germination and seedling growth responses to increased soil moisture variability as might occur with future increases in precipitation variability. Seeds were planted in prairie soil and watered at 1, 2, 4, or 7 d intervals ( I ). Seed germination peaked at I  = 4 d whereas leaf growth in grasses and forbs, and final biomass in grasses peaked at I  = 7 d, suggesting that growth and biomass were favored at greater soil moisture variability than seed germination. Biomass responses to I were stronger than the germination responses, suggesting that soil moisture variability more strongly influenced post germination growth. Individual species responses to I fell into three groups; those with responses to I for: (1) seed germination and seedling survival, (2) biomass, or (3) both germination and biomass production. These species groups may be more useful than life form (i.e., grass/forb) for understanding seed germination and seedling dynamics in grasslands during periods of soil moisture variability. Seed germination and early growth may assume more importance in grassland plant community dynamics under more variable precipitation patterns.

Germination, survival, and growth of grass and forb seedlings: Effects of soil moisture variability

Rice (Oryza sativa L.) provides about 55–80% of the total calories for people in South Asia, Southeast Asia, and Latin America. Elsewhere, it represents a high-value commodity crop. Change in the method of crop establishment from traditional manual transplantation of seedlings to direct seeding has been adopted in many Asian countries in the last two decades, in view of rising production costs, especially for labor and water. Seed invigoration is ascribed to beneficial treatments, applied to the seeds after harvest but prior to sowing, that improve germination or seedling growth or facilitate the delivery of seeds and other materials required at the time of sowing. Many seed invigoration treatments are being employed in a number of field crops, including rice, to improve seedling establishment under normal and stressful conditions. The treatments used to invigorate rice seed include hydropriming, seed hardening, on-farm priming, osmopriming, osmohardening, humidification, matripriming, priming with plant growth regulators, polyamines, ascorbate, salicylicate, ethanol, osmolytes, coating technologies, and more recently presowing dry heat treatments. In the wake of the day-to-day increasing cost of labor and shortage of water, direct seeding approaches in rice cropping systems are the subject of intensive investigation throughout the world and offer an attractive alternative to traditional rice production systems. In this regard, seed invigoration techniques are pragmatic approaches to achieving proper stand establishment in the new rice culture. They help in breaking dormancy and improving seedling density per unit area under optimal and adverse soil conditions. Induction and de novo synthesis of hydrolases, such as amylases, lipases, proteases; and antioxidants such as catalases, superoxide dismutase and peroxidases are reported to be the basis of improved performance using these techniques. The rice seed priming can be performed by soaking simply in water, a solution of salts, hormones, osmoprotectants, matric strain-producing materials, and other nonconventional means. Despite certain limitations, such as water potential, oxygen and temperature, rice seed invigoration has been worthwhile in improving rice yield and quality. Nevertheless, in-depth studies are imperative for understanding the physiological and molecular basis of rice seed priming.

Rice Seed Invigoration: A Review

Moringa oleifera leaf extract (MLE) is rich in amino acids, ascorbate, zeatin, minerals, and many other compounds known for their growth-promoting potential. This study was planned to explore the potential of MLE as a seed priming agent to increase the germination rate and plant vigor of 3 range grasses, i.e. Cenchrus ciliaris, Panicum antidotale, and Echinochloa crusgalli. The priming strategies used were hydropriming, CaCl2, PEG-8000 (-1.1 M Pa), MLE (concentrate; 1:10, 1:20, 1:30, and 1:40 dilutions with distilled water), and matripriming using saturated jute mat for 24 h. The primed seeds were placed between 2 moist Whatman No. 1 filter papers in petri plates to evaluate germination and seedling vigor. Though all of the priming strategies excelled as compared to the control, matripriming and priming with 30× diluted MLE (1:30) were the most effective; thus, they were selected for further experimentation. In the second phase, these optimized priming strategies were used along with hydropriming and an unprimed control in pot studies. Both matripriming and MLE (1:30) priming significantly increased the germination. Matripriming was more effective in increasing the number of leaves, number of tillers, and shoot vigor for Cenchrus ciliaris and Panicum antidotale, but roots were more vigorous when primed with MLE (1:30). In the case of Echinochloa crusgalli, the results were reversed: the number of leaves, number of tillers, and shoot vigor were improved when primed by MLE (1:30), whereas matripriming maximally increased the root length and weight. It was concluded that both MLE (1:30) and matripriming with jute mat can be effectively used as priming agents for these rangeland grasses. Both strategies are low-cost, environmentally friendly, and can easily be adapted by farmers and range managers.

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Moringa oleifera leaf extract: An innovative priming tool for rangeland grasses

Experiments were conducted to examine the effects of cocultivating the important bioenergy crop switchgrass with the ectomycorrhizal fungus Sebacina vermifera under severe drought conditions Plants cocultivated with the fungus produced significantly higher biomass and had a higher macronutrient content than uninoculated control plants under both adequately watered and drought conditions

Enhancement of switchgrass (Panicum virgatum L.) biomass production under drought conditions by the ectomycorrhizal fungus Sebacina vermifera.

Seed dormancy and slow seedling development often limit estab lishment of warm-season grass stands. Establishment of seedlings with two solid matrix seed priming (SMP) treatments [2-d moistened (17°C) and 14-d wet-chill (4°C)] was compared with untreated seed of 'Kaw' and 'Pawnee' big bluestem (Andropogon gerardii Vitman) and 'Path-finder' and 'Cave-in-Rock' switchgrass (Panicum virgatum L.) in greehouse and field experiments. In two greenhouse studies, seedling emergence was monitored from 7 to 26 d after planting and numher of adventitious roots were monitored from 2 to 5 wk after planting. Field experiments were initiated on 19 Apr. 1988, 3 June 1988, and 23 May 1989, on a Sharpsburg silty clay loam (fine montmorillonitic, mesic, Typic Argiudolls) [...]

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Keith Kubik

Papers

Big Bluestem and Switchgrass Establishment as Influenced by Seed Priming