Root traits and yield in sugar beet: identification of AFLP markers associated with root elongation rate

AbstractSilicon is reported to reduce the toxic effects of Al on root elongation but the in planta mechanism by which this occurs remains unclear. Using seedlings of soybean (Glycine max) and sorghum (Sorghum bicolor), we examined the effect of up to 2 mM Si on root elongation rate (RER) in Al-toxic nutrient solutions. Synchrotron-based low energy X-ray fluorescence (LEXRF) was then used for the in situ examination of the distribution of Al and Si within cross-sections cut from the apical tissues of sorghum roots. The addition of Si potentially increased RER in Al-toxic solutions, with RER being up to ca. 0.3 mm h−1 (14 %) higher for soybean and ca. 0.2 mm h−1 (17 %) higher for sorghum relative to solutions without added Si. This improvement in RER could not be attributed to a change in Al-chemistry of the bulk nutrient solution, nor was it due to a change in the concentration of Al within the apical (0-10 mm) root tissues. Using LEXRF to examine sorghum, it was demonstrated that in roots exposed to both Al and Si, much of the Al was co-located with Si in the mucigel and outer apoplast. These observations suggest that Si reduces the toxicity of Al in planta through formation of Al-Si complexes in mucigel and outer cellular tissues, thereby decreasing the binding of Al to the cell wall where it is known to inhibit wall loosening as required for cell elongation.

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Influence of Day and Night Temperature Differentials on Root Elongation Rate, Root Hydraulic Properties, and Shoot Water Relations in Chrysanthemum

Journal of the American Society for Horticultural Science ◽

10.21273/jashs.125.3.383 ◽

2000 ◽

Vol 125 (3) ◽

pp. 383-389

Author(s):

Pauline Helen Kaufmann ◽

Robert J. Joly ◽

P. Allen Hammer

Keyword(s):

Root Elongation ◽

Dark Period ◽

Stem Elongation ◽

Elongation Rate ◽

Light Period ◽

Night Temperature ◽

Diurnal Patterns ◽

Root Elongation Rate ◽

Temperature Regimes ◽

Maximum Root

The difference between night and day temperature (DIF = day - night temperature) has been shown to affect plant height. A positive DIF (+DIF), cooler night than day temperature, increases stem elongation while a negative DIF (- DIF), warmer night than day temperature, decreases stem elongation. The physiological mechanism underlying the growth response to DIF is not understood, however, and the effects of day/night temperature differentials on root permeability to water and root elongation rate have not been studied. The objective of this study was to describe how +DIF and -DIF temperature regimes affect leaf water relations, root water flux (Jv), root hydraulic conductivity (Lp), and root elongation rates of `Boaldi' chrysanthemum [Dendranthema ×grandiflora Kitam. `Boaldi' (syn. Chrysanthemum ×morifolium Ramat.)] plants over time. Leaf turgor pressure (ψp) was 0.1 to 0.2 MPa higher in plants grown in a +6 °C DIF environment throughout both the light and dark periods, relative to those in a -6 °C DIF environment. Jv differed markedly in roots of plants grown in +DIF vs. -DIF environments. Rhythmic diurnal patterns of Jv were observed in all DIF treatments, but the relative timing of flux minima and maxima differed among treatments. Plants grown in positive DIF regimes exhibited maximum root flux at the beginning of the light period, while those in negative DIF environments had maximum root flux during the first few hours of the dark period. Plants grown in +DIF had significantly higher Lp than -DIF plants. Plants grown in +DIF and -DIF environments showed differences in the diurnal rhythm of root elongation. During the dark period, +DIF plants exhibited minimal root elongation rates, while -DIF plants exhibited maximal rates. During the light period, the converse was observed. In -DIF temperature regimes, periods of rapid root elongation coincided with periods of high Jv. Results of this study suggest that negative DIF environments lead to leaf turgor reductions and markedly alter diurnal patterns of root elongation. These changes may, in turn, act to reduce stem elongation.

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