Reactions in chloroplasts, cytoplasm and mitochondria of leaf slices under osmotic stress

Abstract

The effect of osmotic dehydration on metabolic reactions in three different subcellular compartments (chloroplast, cytoplasm and mitochondria) was studied in vacuum-infiltrated thin leaf slices from various plants, in the absence of stomatal control. The reactions tested were CO2 fixation in the light (chloroplast), CO2 fixation in the dark (cytoplasm), and O2 uptake in the dark (mitochondria). In most plants, the sensitivity of dark CO2 fixation to dehydration was similar to the sensitivity of photosynthesis. In leaf slices from a plant with Crassulacean acid metabolism (Kalanchoe pinnata), dark CO2 fixation (which reached similar rates as light fixation) was slightly more sensitive to osmotic stress than photosynthesis. Dark respiration (measured as O2 uptake) was significantly more resistant to hypertonic stress than both types of CO2 fixation. In crude leaf extracts from spinach, the response of soluble enzymes from the three different subcellular compartments to high concentrations of various electrolytes and neutral compounds was examined and compared with the in-vivo data.

Comparative evaluation of hydro-, chemo- , and hormonal-priming methods for imparting salt and PEG stress tolerance in Indian mustard (Brassica juncea L.)

“…The decrease in chlorophyll content might be attributed to the increased degradation of chlorophyll pigments due to stress-induced metabolic imbalance (Ashraf et al 1994). In addition, high osmotic pressure generated under stress has been suggested to create an interference with the de novo synthesis of the structural components of chlorophyll (Kaiser et al 1983). Although, at present, the underlying mechanisms of priming-mediated response is not clear, the results certainly demonstrated the positive effect of seed priming in improving the growth of seedlings under NaCl/ PEG stress.…”

Differential heavy metal tolerance of Arabidopsis halleri and Arabidopsis thaliana: a leaf slice test

“…In the light of this differential hyperaccumulation property of A. halleri shoots, it is of interest to determine the actual leaf tissue tolerance level of A. halleri in comparison to its metal‐sensitive relative A. thaliana . The leaf slice method is an efficient and simple test for effectors because of the easy and defined application technique and has been used, for example, in studying the effect of osmotic dehydration on carbon fixation (Kaiser et al ., 1983) and is also useful in analysing changes in leaf gene expression (Horling et al ., 2002; A. Kandlbinder et al ., unpublished). Tissue tolerance tests for hydrophilic compounds such as heavy metals cannot be adequately performed with intact leaves, because metal permeability through the cuticle and stomates is low and difficult to control and the intratissue distribution undefined.…”

Leaf K+ Interaction with Water Stress Inhibition of Nonstomatal-Controlled Photosynthesis

“…Boyer and Younis (9) suggest that increased Mg2e concentration in the dehydrated stroma inhibits photosynthesis. Kaiser (15,17) has presented correlative evidence supporting a hypothesis that stromal volume reduction upon dehydration increases the K+ concentration, which then inhibits photosynthesis. Berkowitz and Gibbs (4, 5) have indicated that upon dehydration, stromal pH is too low to support optimal photosynthesis, and that raising the stromal pH partially reverses this inhibition.…”