Expansion dynamics, metabolite composition and substance transfer of the primary root growth zone ofZea maysL. grown in different external nutrient availabilities

Abstract

A combined analysis of growth and metabolite composition was performed in primary roots of Zea mays L. (Var. Alexander). The seedlings were hydroponically cultivated either in pure water or in complete nutrient solution. The overall root growth performance was similar in both treatments. Yet, digital image sequence processing methods resolved, that growth distribution and oscillatory movements within the growth zone depended strongly on external nutrient availability. Metabolite concentration profiles were similar in both treatments for most investigated metabolites, indicating a thorough mobilization of nutrient resources from the seed, but concentrations of glutamine, glutamic acid, NO 3 -, NH 4 + + + + , malate and citrate showed pronounced differences between treatments. No diurnal variations in metabolite concentrations were found. Deposition rate profiles were in general more similar to relative elemental growth rate profiles than concentration profiles and were not affected by the treatment. Major ions were deposited maximally in front of the centre of growth activity, while greatest hexose deposition was found behind that. Relative to their abundance in the root growth zone, net rates of transfer from mature tissue were highest for sucrose, glutamic acid and aspartic acid, whereas glucose, fructose and most amino acids inversely showed high net rates of transfer out of the root growth zone, indicating a high catabolic rate for those substances there. NO 3 -, but not other nutrients, was transferred to a great extent from the root growth zone to the mature tissue in nutrient solution. Overall, the results show, that a careful analysis of growth dynamics allows quantifying and interpreting a number of important flux parameters in the growing organ and that the performance of the primary root does not depend strongly on external nutrient availability.

Aphid Infestation Causes Different Changes in Carbon and Nitrogen Allocation in Alfalfa Stems as Well as Different Inhibitions of Longitudinal and Radial Expansion

“…Where mass density of a nutrient is steady, the integral of the deposition rate over distance represents the total net deposition of nutrient sustaining the growth in the region (Bret-Harte and Silk, 1994;Walter et al, 2003). This integral is the product of local density and growth velocity and may also be considered as the growth flux of the nutrient associated with displacement of the tissue element (see ''Materials and Methods'').…”

“…where r(x) for water, dry matter, carbon, or nitrogen was determined as described above and v(x) is the growth velocity of displacement from the apex, determined as the integral of g(x) along x (Bret-Harte and Silk, 1994;Walter et al, 2003). Where the mass density profile is steady, i.e.…”

“…Silk, 1984;Muller et al, 1998;van der Weele et al, 2003;Walter et al, 2003), monocot leaves (Schnyder and Nelson, 1989;Ben Haj Salah and Tardieu, 1997;Maurice et al, 1997), and dicot leaves (Lecoeur et al, 1995;Granier and Tardieu, 1999). These kinematic studies have also been widely used to study the influence on growth of environmental factors such as light (Schnyder and Nelson, 1989), water deficit (e.g.…”

Temperature responses of roots: impact on growth, root system architecture and implications for phenotyping

“…A plastic rhizotron base plate, inclined by 68 towards the horizontal plane, was used to hold the seedlings. Nutrient solution containing full strength Ingestad nutrient solution (Ingestad 1982;Walter et al 2003) was flushed constantly over the growing roots. The solution was collected in a plastic basin (volume 10 L) and was circulated back to the top of the rhizotron plate continuously.…”

Analysis of movement in primary maize roots

“…Generally, CNs are described by the amplitude of the apex deflection and by the period of movement duration or its frequency. There are two types of CNs in roots: long-period nutations with duration of 40-90 min per cycle and short-period nutations or micronutations characterised by duration of approximately 7-15 min per cycle (Shabala & Newman 1997;Walter et al 2003;Shabala 2003). Although these movements are endogenous, their descriptive parameters (i.e., frequency and amplitude) may be affected by gravity (Brown 1993) and by mechanical (Ishikawa & Evans 1992) and chemical stimulations (Hayashi et al 2004).…”