Accumulation and partitioning of biomass and soluble carbohydrates in maize seedlings as affected by source of nitrogen, nitrogen concentration, and cultivar¹

Abstract

Seedlings of four maize hybrids were grown hydroponically to investigate the impact of different N sources (Ca(NO 3 ) 2 , (NH 4 ) 2 SO 4 and a 1:1 mixture of both) on (i) production and partitioning of root and shoot dry matter, (ii) concentration of soluble carbohydrates in roots and shoots and their partitioning to these plant parts, (iii) concentration of starch in the shoot, and (iv) N uptake. During the main phase of the experiments (duration 14d), the plants were grown in a greenhouse at 25/22°C day/night temperatures and a photoperiod of 16h. Nitrogen was supplied at three concentrations (2.8, 28, and 280 ppm).The root-zone pH was 6.5. Under the lowest N supply, the N sources produced similar root and shoot dry matters. At the highest N level (280 ppm), NO 3 -fed plants were superior. In contrast, the mixture of NH 4 and NO 3 -was optimum at 28 ppm. More or less pronounced N form by N concentration interactions were also found in the concentration and distribution of soluble carbohydrates and in all remaing traits. There were almost statistically significant cultivar by N form interactions in shoot dry matter (P = 0.07) and total dry matter (P = 0.06), indicating the existence of considerable genotypic variation in sensivity to NH4-N.

Nitrogen Under‐ and Over‐supply Induces Distinct Protein Responses in Maize Xylem SapF

“…To better understand the potential roles of nitrogenous compounds in xylem sap in regulating plant N homeostasis, the amounts of nitrogenous compounds in xylem sap were analyzed, and it was found that N under‐supply decreased nitrate‐ and total N content in xylem sap (Table 1). Since nitrate may serve as a signal to mediate plant N metabolism and development (Crawford and Glass 1998), a nitrate‐N decrease in xylem sap might trigger biological programs that promote carbohydrate allocation from shoots to roots, stimulate root growth, and increase total root length (Henry and Raper 1991; Alfoldi et al 1992; Lopez‐Bucio et al 2003; Hermans et al 2006) (Figure 1B). Due to moderate N oversupply and the enormous buffering capacity of soils (Barber 1995), less effects were derived from HN treatment than that from LN treatment except for a significant increase in total N content in roots (Figure 1A).…”

Full‐Season Retrospectives on Causes of Plant‐to‐Plant Variability in Maize Grain Yield Response to Nitrogen and Tillage

“…The negative consequences of increasing NH 3 rate, and decreasing depth of application or time interval between NH 3 application and planting on maize seedling emergence and early growth development was documented decades ago (Colliver and Welch, 1970a). Reductions in root dry matter were also observed with higher rates of ammonium‐N (NH 4 –N) in studies that involved different forms of N sources (ammonium‐hydroxide, ammonium‐nitrate, ammonium‐sulfate, calcium‐nitrate, potassium‐nitrate), due to higher aqueous NH 3 concentrations (Bennett et al, 1964; Warncke and Barber, 1973; Errebhi and Wilcox, 1990; Alföldi et al, 1992; Schortemeyer and Feil, 1996). The ammonia toxicity may be universal among plant species (Britto and Kronzucker, 2002), but the sensitivity between species (Errebhi and Wilcox, 1990; Dowling, 1998; Britto and Kronzucker, 2002) and among maize cultivars/hybrids (Bennett et al, 1964; Alföldi et al, 1992; Schortemeyer and Feil, 1996; Schortemeyer et al, 1997) in actual visible toxicity symptoms can differ substantially (Bennett et al, 1964; Bennett and Adams, 1970; Colliver and Welch, 1970b; Creamer and Fox, 1980; Errebhi and Wilcox, 1990; Alföldi et al, 1992; Schortemeyer and Feil, 1996; Dowling, 1998).…”

Híbridos e variedades de milho submetidos à inoculação de sementes com Herbaspirillum seropedicae

“…As interações entre cultivares de milho e bactérias fixadoras de N e/ou promotoras de crescimento são dependentes de especificidades na interação entre genótipos da planta e estirpes dos microrganismos envolvidos (ALFOLDI; PINTER; FEIL, 1992;gARCIA DE SALOMONE;DöBEREINER, 1996;MACHADO et al, 2001). O insucesso no crescimento e teor de N encontrado na maioria dos genótipos de milho submetidos à inoculação com Herbaspirillum seropedicae (ZAE 94) confirma a situação de baixa interação entre os simbiontes, pois menos de 20% dos genótipos avaliados foram responsivos à inoculação.…”