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1

Contributions of arbuscular mycorrhizal fungi to growth, photosynthesis, root morphology and ionic balance of citrus seedlings under salt stress

100%
Wu Q.-S., Zou Y.-N., He X.-H.
Acta Physiologiae Plantarum
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2010
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tom 32
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nr 2
A pot study was conducted to determine the effects of arbuscular mycorrhizal (AM) fungi (Glomus mosseae and Paraglomus occultum) and salt (NaCl) stress on growth, photosynthesis, root morphology and ionic balance of citrus (Citrus tangerine Hort. ex Tanaka) seedlings. Eighty-five-day-old seedlings were exposed to 100 mM NaCl for 60 days to induce salt stress. Mycorrhizal colonization of citrus seedlings was not affected by salinity when associated with P. occultum, but significantly decreased when with G. mosseae. Compared with the non-mycorrhizal controls, mycorrhizal seedlings generally had greater plant height, stem diameter, shoot, root and total plant biomass, photosynthetic rate, transpiration rate and stomatal conductance under the 0 and 100 mM NaCl stresses. Root length, root projected area and root surface area were also higher in the mycorrhizal than in the nonmycorrhizal seedlings, but higher root volume in seedlings with G. mosseae. Leaf Na⁺ concentrations were significantly decreased, but leaf K⁺ and Mg²⁺ concentrations and the K⁺/Na⁺ ratio were increased when seedlings with both G. mosseae and P. occultum. Under the salt stress, Na⁺ concentrations were increased but K⁺ concentrations decreased in the mycorrhizal seedlings. Under the salt stress, Ca²⁺ concentrations were increased in the seedlings with P. occultum or without AM fungi (AMF), but decreased with G. mosseae. Ratios of both Ca²⁺/Na⁺ and Mg²⁺/Na⁺ were also increased in seedlings with G. mosseae under the non-salinity stress, while only the Mg²⁺/ Na⁺ ratio was increased in seedlings with P. occultum under the salt stress. Our results suggested that salt tolerance of citrus seedlings could be enhanced by associated AMF with better plant growth, root morphology, photosynthesis and ionic balance.
2
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The change of root morphology of Plantago lanceolata under hypoxia conditions

100%
Banach K., Visser E. J. W., Stepniewska Z., Banach A. M.
Acta Agrophysica
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2012
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tom 19
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nr 2
Many plant species can adapt to flooding and hypoxia by forming a root system with an altered architecture: thicker, shorter and shallower adventitious roots, than under aerated conditions. The internal gas transport is often improved by increased root porosity and aerenchyma, which is tissue with large intercellular spaces. The raised root aeration allows better supply of oxygen to plant tissues and diffusion of oxygen into the rhizosphere (Radial Oxygen Loss, ROL). This phenomenon creates narrow, but well aerated zones in the hypoxic soil, where phytotoxins are oxidised and methanotrophic as well as nitrifying bacteria can live. The aim of the study was to determine the change of root archi-tecture, porosity and ROL from roots of Plantago lanceolata plants originating from The Middle Vistula River Gorge. Selected plant species were subjected to transient flooding during 7 days of culti-vation on aerated and stagnant oxygen-deficient hydroponic medium. We observed the formation of shorter hypoxic, adventitious roots (56-69 mm) than control roots (112-196 mm) with high porosity (stagnant 15-21 %, control 8.5-9.4%), and the diameter of aerated zone (halo) increased from control values of 0-1.5 mm to 2-2.5 mm under hypoxic conditions.
3

Response of silver birch [Betula pendula Roth.] seedlings to experimental variation in aluminium concentration

100%
Bojarczuk K., Oleksyn J., Karolewski P., Zytkowiak R.
Polish Journal of Ecology
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2006
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tom 54
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nr 2
The process of soil degradation and destabilization of forest ecosystem by industrial pollution is frequently associated with mobilization of toxic Al³⁺ ions. Both these processes exert a negative influence on tree root systems and may even result in the decline of whole forest stands. One-year-old seedlings of silver birch (Betula pendula Roth.) grown in pots were treated with a range of aluminum sulfate concentrations in order to test the effects of Al on growth, root structure, content of phenolic compounds and mineral nutrition of roots and foliage. Plants exposed to Al concentrations exceeding 50 mg Al dm⁻³ had reduced growth, root structure and nutrient uptake were affected, and a substantial increase of Al concentration occurred in foliage and roots. Concentration of several elements in the foliage and roots declined with increasing Al concentration, including Mg and Ca, and to a lesser extent, P, K, and Na. Most root traits such as root mass or root growth rate were more strongly affected by Al than the foliage. Changes in root Ca, Al and Ca:Al ratio, and root morphology were detected at the lowest Al concentration (50 mg Al dm⁻³) indicating usefulness of these traits as early indicators of adverse aluminum effects on plants.
4

Effect of patchy distribution of soil nutrients on root morphology and biomass allocation of selected grassland species: experimental approach

80%
Zaller J. G.
Polish Journal of Ecology
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2007
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tom 55
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nr 4
Nutrient distribution in natural habitats is usually patchy in space and time, however most knowledge about plant growth and behaviour is based on experiments conducted under spatially homogenous conditions. Evidence has accumulated that the growth and competitive interaction of plant species are strongly affected by heterogeneous rather than homogeneous resource distribution, even when the total resource supply remains similar. For this study it is hypothesized that infestations of grasslands with the nitrophilous weed Rumex obtusifolius L. (broadleaved dock) are partially the consequence of its ability to exploit spatial nutrient heterogeneity. This was tested in a full-factorial pot experiment with homogeneously or heterogeneously distributed nitrogen and/or potassium at either normal or increased soil moisture where R. obtusifolius was grown together with three other grassland species (grass: Arrhenatherum elatius L., non-leguminous herb: Taraxacum officinale Weber, leguminous herb: Trifolium repens L.). The species differed significantly in their root morphology (root length and diameter, specific root length, number of root tips) and biomass allocation response to nutrient distribution, as well as to the nutrient type used to create patches and to soil moisture (e.g., significant species × treatment interactions). Generally, the root system of A. elatius showed the highest plasticity to imposed treatments, followed by T. officinale, R. obtusifolius and T. repens. Unexpectedly, root morphology of R. obtusifolius was unresponsive to soil heterogeneity and less responsive to nutrient type and irrigation than that of the other species. Nutrient type used to create patches influenced the biomass allocation to the root system of R. obtusifolius while nutrient distribution and irrigation showed no effect on biomass allocation. Exploitation of soil nitrate-nitrogen and potassium was similar among species but exploitation was individually affected by nutrient type, nutrient distribution and irrigation suggesting that species-specific differences in nutrient storage capacities in roots or adjustments regarding root nutrient uptake kinetics may play an important role. Results from this study show that R. obtusifolius does not seem to have superior traits to utilize soil nutrient heterogeneity, certain nutrient types or higher soil moisture that differentiates it from the other grassland species tested. The observed effects might have consequences for the long-term competitive relationships between species in the grassland community suggesting that cultural and biological management measures oriented towards the improvement of the competitive ability of co-occurring grassland species might also be important in heterogeneous soils.
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