Changes in photosynthesis, dark respiration rates and photosynthetic carbon partitioning in winter rye and wheat seedlings during cold hardening

摘要

In winter rye and wheat seedings the ratio of light-saturated photosynthesis rate to that of dark respiration increased about 2- to 3-fold after cold hardening while the initial difference in the value of this parameter between the species (it was 40% higher in rye than in wheat seedlings) was kept. Cold hardening of both species resulted in a marked increase in the contents of sugars, lipids and cytoplasmic proteins in leaf tissues, in the ratios of high molecular weight polypeptide content to that of low molecular weight ones, of membrane lipid content to that of membrane proteins, of phospholipid content to that of sterols, of unsaturated fatty acid content to that of saturated ones, of relative cross-section area of chloroplasts to that of a single cell and of the same area of plastoglobules to that of a single chloroplast. These results suggest that the changes observed in the above parameters reflect the development of additional assimilate sinks at various levels of plant structural organization to maintain a sufficiently high rate of photosynthesis at low temperature. According to the data obtained, under these conditions rye seedlings develop a higher sink capacity than wheat seedlings and for this reason likely exhibit more effective frost adaptation.