Concentrations of inorganic and organic solutes in extracts from individual epidermal, mesophyll and bundle-sheath cells of barley leaves

Abstract

Abstract. The distribution of solutes between epidermal, mesophyll and bundle-sheath cells in barley (Hordeum vulgare L. cv. Klaxon) leaves was studied by analysing extracts obtained from single cells with a modified pressure probe. Activity of the cytoplasmic marker enzyme, malate dehydrogenase, revealed that epidermal cell extracts were completely vacuolar in origin, but extracts from mesophyll cells also contained cytoplasmic constituents. The extracts were analysed for osmolality and the concentrations of K, Na, Ca, C1, P, S, NO3, sugars and total amino acids. Epidermal and mesophyll cell extracts had similar osmolalities but these varied between 420 and 565 mosmol 9 kg ~ depending on the leaf developmental stage; the osmolality of bundle-sheath extracts was approximately 100 mosmol -kg ~ lower. Under the growth conditions used, K and NO3 were found in all three cell types and their concentrations generally ranged between 180 and 230 mM. In contrast, Ca was almost restricted to epidermal cells, where it increased to 70 mM during leaf ageing. Phosphorus was only detectable (_> 5 mM) in extracts from mesophyll and bundle-sheath cells, while C1 concentrations were highest in epidermal and lowest in mesophyll cell extracts. The concentrations of sugars and amino acids were close to the detection limit (approx. 2 mM) in epidermal cells but mesophyll cells contained total sugar (glucose, fructose and sucrose) of up to 78 mM and total amino-acid concentrations of up to 13.5 mM. Concentrations in bundle-sheath cells were intermediate between those in the epidermis and mesophyll.

Patterns of solute in individual mesophyll, bundle sheath and epidermal cells of barley leaves induced to accumulate carbohydrate

“…6 a), the total concentration of sugars was c. 50-70 mM for mesophyll and bundle sheath cells. In the epidermal cells the sum of the sugar concentration was < 10 mM, in good agreement with the data obtained by Fricke et al (1994) by the same technique and with the results of Dietz et al (1994) obtained using isolated epidermal protoplasts. In both mesophyll and bundle sheath cells, concentration of sucrose was about 30-50 mM at the beginning of the light period, when the fructose concentration was very close to that of sucrose in mesophyll cells.…”

Patterns of solute in individual mesophyll, bundle sheath and epidermal cells of barley leaves induced to accumulate carbohydrate

“…The epidermis of barley leaves could be an intermediary storage compartment for sugars and contain as much as 5-15 % of the leaf's glucose and fructose (Dietz, Hollenbach & Hellwege, 1994). However, in other studies the epidemis was shown to contain extremely low concentrations of sugars, c. 2 mM (Fricke, Leigh & Tomos, 1994).…”

The AtProT Family. Compatible Solute Transporters with Similar Substrate Specificity But Differential Expression Patterns

“…Differential compartmentation of inorganic ions between the mesophyll and the upper and lower epidermis of leaves has been reported for a number of monocotyledonous and dicotyledonous species (Karley et al, 2000). Also, sugars and amino acids are not evenly distributed in barley leaves, with concentrations being much lower in the epidermis (Dietz et al, 1994;Fricke et al, 1994). Unfortunately, in these very detailed studies, the techniques used for derivatization and detection of amino acids were not suitable for analyzing Pro concentrations.…”