Influence of seed nitrogen content on seedling growth and recovery from nitrogen stress

Abstract

In low fertility conditions, germinating seedlings are heavily dependent upon N from seed reserves for growth and development. Experiments were conducted to examine the influence of seed N content and mobilization on leaf development and the ability to take up nitrate and up-regulate leaf growth processes during recovery from the period of N deprivation. Genetically homozygous soybean lines with a range of seed N contents were grown in hydroponics culture without an external N source. Microscopic analyses of the apical meristem and plant exposure to labeled 15 N-nitrate allowed precise descriptions of changes in leaf initiation and nitrate uptake during recovery. In seedlings grown without N, inhibitions of leaf expansion and leaf initiation were detectible in the 2nd week after germination, and both were inversely related to the amount of N released from the seed. The S/R ratio decreased, indicating early N stress, but the S/R adjustments were not proportional to the degree of N stress as occurs with older plants, suggesting limitations in C availability. When external N was supplied to plants after 15 or 23 days of N deprivation, the induction period for nitrate uptake was longer than that normally observed with N-replete seedlings, and rates of growth during recovery from the N stress were correlated with initial seed N contents. The inhibition of individual leaf expansion was released only if leaves were at an early developmental stage. Leaf initiation at the apical meristem immediately responded to the presence of external nitrate, with initiation rates approaching those for +N controls. The results indicate that seedling vigor in infertile conditions and the ability to respond to available N are strongly influenced by seed resources.

Seed nutrient content and nutritional status of Posidonia oceanica seedlings in the northwestern Mediterranean Sea

“…nutrients, defoliation, herbivores and pathogens) depends, in large part, by the amount of reserves originally available to the seedlings (Foster 1986, Mazer 1989, Houssard & Escarré 1991, Seiwa & Kikuzawa 1991, Milberg & Lamont 1997, Bonfil 1998, Tyler & Zohlen 1998, Naegle et al 2005. A number of studies have demonstrated that seed mass is a major determinant of seed reserves, and substantial seed mass variation exists at many scales (i.e.…”

Seed Nitrogen Mobilization in Soybean: Effects of Seed Nitrogen Content and External Nitrogen Fertility

“…At this early stage of development, seedlings do not possess the degree of 'morphological plasticity' that is present later on. As shown previously, slower seedling growth is associated with reduced leaf canopy development, but not proportionate enhancement of root growth (Naegle et al, 2005). The adjustment in shoot and root growth ratios is considered to be a key acclimation strategy for survival and competitiveness in low N environments (Chapin, 1988(Chapin, , 1991Rufty, 1997).…”

“…Cotyledonary N content decreased exponentially ( Figure 1A; Naegle et al, 2005). Amounts of N released reflected differences in the initial seed N content.…”

“…In a recent study, we began to evaluate seedling growth responses using soybean genotypes with a range of N contents (Naegle et al, 2005). Under low fertility conditions, it was found that lower seed N contents were associated with slower seedling growth, decreased leaf initiation and expansion, and reduced ability to respond to an external N supply.…”

The effect of defoliation by Cameraria ohridella Deschka and Dimic (Lepidoptera: Gracillariidae) on seed germination and seedling vitality in Aesculus hippocastanum L.

“…These reserves contain mainly nutrients and constitute a key factor to seedling vitality (Lu and Koide, 1991). Seeds containing larger amounts of nutrients usually produce more vigorous seedlings (Naegle et al, 2005). Therefore, the quick exhaustion of stored reserves and the smaller amount of nutrients in the seeds justify the lower height increment and vitality (e.g.…”