Sugar loading is not required for phloem sap flow in maize plants

Abstract

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Comparative analyses of the metabolite and ion concentrations in nectar, nectaries, and leaves of 36 bromeliads with different photosynthesis and pollinator types

“…A similar composition of the inorganic ions was found in nectar of other plant species, such as different species of Nicotiana (Tiedge and Lohaus, 2017). Potassium and chloride are also the most abundant inorganic ions in the phloem sap of different plant species (Lohaus et al, 2000;Babst et al, 2022;Lohaus, 2022), which suggests that the nectaries are supplied with inorganic ions via the phloem. Whereas, the inorganic ion composition is comparable in nectar and nectaries, their concentration is much lower in nectar than in nectaries (Figure 4).…”

“…In some studies, the concentrations of amino acids or inorganic ions in nectar were also related to the respective pollinators, which was shown for several species of the genus Nicotiana (Tiedge and Lohaus, 2017) or numerous species of Bromeliaceae (Göttlinger et al, 2019). Amino acids in nectar are an important source of nitrogen for some flower visitors like many adult insects; hummingbirds, however, are primarily insect-catchers, and bats also use insects and pollen as an additional nitrogen source (Baker, 1977;Herrera et al, 2001). Therefore, these vertebrates are not dependent on nectar as sole nitrogen source (Baker, 1977).…”

“…Amino acids in nectar are an important source of nitrogen for some flower visitors like many adult insects; hummingbirds, however, are primarily insect-catchers, and bats also use insects and pollen as an additional nitrogen source (Baker, 1977;Herrera et al, 2001). Therefore, these vertebrates are not dependent on nectar as sole nitrogen source (Baker, 1977). Inorganic ions in nectar are believed to affect the electrolytic balance of the visitors (Hiebert and Calder, 1983).…”

Smoke exposed roots causes reduced whole-plant vascular sectoriality

“…This challenges our fundamental thinking of plant carbon allocation and source-sink relations where according to existing dogma established 90 years ago in the Münch Hypothesis (Münch, 1930), the supply of carbon in leaves is what drives a mass gradient of sugar in the phloem propelling bulk flow in long-distance transport to sink tissues. However, according to findings recently published (Babst et al, 2022) this fundamental theory is being challenged. Our findings support this challenge in that the speed of movement within the phloem appears independent of a mass gradient.…”

The Surprising Dynamics of Electrochemical Coupling at Membrane Sandwiches in Plants

“…Long-distance transport in the phloem of vascular plants bridges the distance between the green tissues where photosynthesis occurs and heterotrophic organs, such as roots, flowers, and fruits, where the products of photosynthesis are used for growth and/or storage. Via the phloem vasculature, various molecules synthesized in the leaves (e.g., sugars, amino acids, and other nitrogenous or phosphorus-containing compounds) are transported alongside inorganic ions from the source tissues, which produce more assimilates than they need, to the consuming sink tissues [ 12 ]. The transport phloem between source and sink tissues is not a passive transport tube, but a living tissue that also contributes significantly to the maintenance and growth of the plant axis.…”