Nitrogen Effects on Seed Germination and Seedling Growth

Abstract

Recent evidence associates the persistence of invasive plant species with disturbance and fluctuations in distinct forms of mineral N in soils. We conducted soil and hydroponic experiments to investigate the influence of N form and availability on germination and seedling development of 2 invasive annual grasses, cheatgrass (Bromus tectorum) and medusahead (Taeniatherum caput-medusae) and 6 perennial grasses, bluebunch wheatgrass (Pseudoroegneria spicata), crested wheatgrass (Agropyron cristatum x A. desertorum), Sand Hollow and Seaman's Gulch big squirreltail (Elymus multisetus), and Little Camas and Little Wood bottlebrush squirreltail (E. elymoides ssp. brevifolius and E. elymoides ssp. elymoides, respectively). Seeds were sown in soils with no soil additions, barley straw (1 mg kg 1), NH4+ =10 mg N kg 1, NH4+ + I (nitrification inhibitor) = 10 mg N kg 1 + 37 ml nitrapyrin, or N03' =10 mg N kg1 to evaluate cumulative germination percentage for 20 days in an incubator. For the hydroponic experiment, grass seedlings were exposed to distinct forms and uniform concentrations of mineral N to monitor root and shoot growth for 21 days. Treatments were no N added, NH4+ (1 mM), N03-(1 mM), and NH4NO3 (0.5 mM). Treatments did not alter germination in the soil experiment. Lack of soil N effect on seed germination is attributed to the absence of seed dormancy in the populations of grasses we evaluated. Initial root length and overall shoot growth of grasses were greater in the N03-than in the NH4+ treatment more frequently for perennial grasses. Root and shoot growth of medusahead and cheatgrass generally exceeded that of the other grasses except crested wheatgrass. However, relative decreases in root dry mass for the no N treatment were greater for the invasive annual grasses than the perennial grasses when compared to the N-addition treatments.

Effects of Atmospheric-Pressure N2, He, Air, and O2 Microplasmas on Mung Bean Seed Germination and Seedling Growth

“…Under natural conditions, nitrogen bound in soil mainly exists in four types of compounds - ammonium salts (NH 4 + ), nitrates (NO 3 − ), proteins and products of protein decomposition (amino acids, amines, peptides and humus compounds). It is justifiable to assume that a favorable environment for mung bean seed germination might occur in solutions containing a proper source of nitrogen, thus improving the nutritional values of the solutions 50 51 . Using LNF as feed can increase nitrogen accumulation in the mung bean plant and improve the activity of nitrate reductase and glutamine synthetase related to nitrogen metabolism and photosynthesis, which contributes to the growth of seedling 52 .…”

Nitrogen addition can improve seedling establishment of N‐sensitive species in degraded saline soils

“…However, the decrease in radicle length in L. chinensis may have been due to the increasing seedling N concentration. N is known to have a negative influence on root growth and development (Monaco et al, ; Westwood & Foy, ) and to cause shifts in biomass allocation (Andrews, Raven, & Lea, ; Irving, ). This is paralleled by field studies where in the moderate and severe saline–sodic grasslands of northeastern China, L. chinensis shoot length was enhanced by N application (Huang et al, ).…”

Native plants fare better against an introduced competitor with native microbes and lower nitrogen availability

“…Both seedling emergence and survival were negatively affected by elevated N availability for Oligoneuron . The few studies that have examined germination or seedling emergence of native and exotic species with varying N availability or for different forms of N observed no effect ( Monaco et al 2003 ; LeJeune et al 2006 ) or a negative effect of high nitrate on emergence for some native species ( Boudell and Stromberg 2015 ). Ammonium can be toxic to sensitive species, particularly those in soils that naturally contain little N as ammonium ( Bobbink et al 2010 ); susceptibility of native tallgrass species such as Oligoneuron to ammonium toxicity and differences in susceptibility between native and exotic species deserve further study.…”