Shoot

About: Shoot is a research topic. Over the lifetime, 32188 publications have been published within this topic receiving 693348 citations.

Effects of a vesicular-arbuscular mycorrhizal fungus and other soil microorganisms on growth, mineral nutrient acquisition and root exudation of soil-grown maize plants

Abstract: Maize (Zea mays L. cv. Alize) plants were grown in a calcareous soil in pots divided by 30-μm nylon nets into three compartments, the central one for root growth and the outer ones for hyphal growth. Sterle soil was inoculated with either (1) rhizosphere microorganisms other than vesicular-arbuscular mycorrhizal (VAM) fungi, (2) rhizosphere microorganisms together with a VAM fungus [Glomus mosseae (Nicol. and Gerd.) Gerdemann and Trappel], or (3) with a gamma-irradiated inoculum as control. Plants were grown under controlled-climate conditions and harvested after 3 or 6 weeks. VAM plants had higher shoot∶root ratios than non-VAM plants. After 6 weeks, the concentrations of P, Zn and Cu in roots and shoots had significantly increased with VAM colonization, whereas Mn concentrations had significantly decreased. Root exudates were collected on agar sheets placed on the interface between root and hyphal compartments. Six-week-old VAM and non-VAM plants had similar root exudate compositions of 72–73% reducing sugars, 17–18% phenolics, 7% organic acids and 3% amino acids. In another experiment in which root exudates were collected on agar sheets with or without antibiotics, the amounts of amino acids and carbohydrates recovered were similar in VAM and non-VAM plants. However, threeto sixfold higher amounts of carbohydrates, amino acids and phenolics were recovered when antibiotics were added to the agar sheets. Thus, the high microbial activity in the rhizosphere and on the rhizoplane limits the exudates recovered from roots.

Salt tolerance of the coastal salt marsh grass, Sporobolus virginicus (L.) kunth

Abstract: summary Growth responses, leaf water and osmotic relations, and tissue ionic and organic solute contents of Sporobolus virginicus (L.) Kunth, grown under solution culture in salinities of up to 450 mM NaCl, were studied. Shoot growth was stimulated by intermediate salt levels, concurrent with both an accumulation of Na+ and Cl− in shoots and a slight increase in shoot succulence. Root growth was stimulated at salinities of up to 450 mM NaCl, Osmotic adjustment of shoots was predominantly due to Na+, Cl−, and soluble carbohydrate accumulation, though a slight reduction in shoot succulence may have played a minor role at high salinity. Shoot Na+ and Cl− accumulation was tightly controlled, not exceeding levels required for osmotic adjustment, due in part to ion secretion by leaf salt glands. Shoots were selective for K+ over Na+, maintaining fairly constant K+ concentrations with increasing salinity, resulting in relatively high K+/Na+ ratios at high salinity. Increasing NaCl stimulated the accumulation of K+ in roots, which may have acted as a reservoir of K+ for shoots at high salinity. Glycinebetaine, and to a lesser extent proline and trigonelline, accumulated in shoot tissues with increasing salinity, though trigonelline concentrations were insufficient to be osmotically significant. Accumulation was closely associated with increases in shoot sap osmolality. It is proposed that glycinebetaine may act as a compatible solute in S. virginicus, as levels were sufficiently high to effect total osmotic adjustment of the cytoplasm at high salinity.