Sv. Klimov et al., Changes in photosynthesis, dark respiration rates and photosynthetic carbon partitioning in winter rye and wheat seedlings during cold hardening, J PLANT PHY, 155(6), 1999, pp. 734-739
In order to elucidate whether there is any correlation between freezing tol
erance of plants and some parameters characterizing their source-sink relat
ions at: different levels of plant structural organization, a number of cer
tain responses of winter rye and wheat seedlings to cold hardening was dete
rmined. It has been found that in both crops the ratio of light-saturated p
hotosynthesis rate to that of dark respiration increased about 2-3-fold aft
er hardening while the initial difference in the value of this parameter (i
t was higher by about 40 % in rye seedlings as compared with that in wheat
seedlings) was kept. In addition, cold hardening of both crops resulted in
a marked increase in the contents of sugars, lipids and cytoplasmic protein
s in leaf tissues, in the ratios of high-mol.-wr. polypeptide content to th
at of low-mol.-wt. ones, of membrane lipid content to that of membrane prot
eins, of phospholipid content to that of sterols, of unsaturated fatty acid
content to that of saturated ones, of relative cross-section area of chlor
oplasts 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 observ
ed in the above parameters reflect the development of additional assimilate
sinks at various levels of plant structural organization to maintain a suf
ficiently high rate of photosynthesis at low temperature. According to the
data obtained, under these conditions rye seedlings develop a higher sink c
apacity than wheat seedlings and for this reason likely exhibit more effect
ive frost adaptation as compared with that of the latter crop.