Abstract
The concentrations of deuterium oxide (D2O) in the root tissue water of winter rye seed lings equilibrated with the external D2O concentration within 30 min and in the shoot tissue water after 5-6 h. The equilibrated value in the root water was 87% and in the shoot water , 55%
Abstract
of the external concentration.
Abstract
The K+ absorption rate of the seedlings decreased from a value of 39 to 18,umol g-1 h-1 when the D2O concentration was changed through a range from 0% to 97%. D2O suppressed the absorption of water and K+ by the seedlings . The higher the D2O concentration the greater the suppression , but it was less than with similarly treated rice plants.
Abstract
However, the process of D2O absorption by the seedlings was similar to that of rice seedlings (Envir, exp . Bot., 24, 369).
Introduction
Among the higher plants winter rye is known to , be resistant to deuterium oxide (DO):
Introduction
Winter rye is able to germinate and grow in 99% D2O1) without the prior adaptation usually found to be required2). Some biochemical processes of winter rye are known to be affected by D2O3)4), but the physiological features have not yet been clarified as they have been in the case of rice. Rice, which belongs to the same family Gramineae as rye, is affected greatly by D20 on the absorptionn processes of water5) and ions6)-8), and on the germination process of seeds).
Introduction
We aimed to further illustrate 'the resistance' of rye with finding how the absorption of water and ions is affected by D20. with the 87% concentration of the root tissue water (Fig. 1) . The D2O concentration remained practically unchanged from the base to the top of the protective sheath (coleoptyle apex). At the upper parts of the sheath the concentration decreased sharply toward the leaf apex and reached a value less than 20% of that of the external solutions. The distribution pattern did not change over the D2O concentration of culture solutions ranging from 0% to 96%. 
Introduction
May 1985 Fig. 4 D20 suppression curves of potassium ion absorption and germination of winter rye. Relative K+ absorption rates were obtained from the slopes of the curves in Fig. 3(a) . Relative germination rates were expressed as "the time required for 50% -germination" obtained from germination curves. Broken line shows the result on K+ absorption by rice seedlings8).
Introduction
4. The D20 suppression curve for K+ absorption by the roots, was linear on a semilog scale and had a gentle slope compared with that of rice seedlings8). The degree of suppression was not as great as that of rice seedlings. This means that in regard to ion absorption rye seedlings are more resistant to D20 than are rice seedlings.
Introduction
The linear relation between the degree of sup pression of the ion absorption and the D20 concentration suggests that there is no threshold of D2O concentration at which suppression occurs.
Introduction
The amount of K+ translocated from the roots to the shoots increased exponentially with ab sorption time (Fig. 3(b) 

{'paper_id': '37331579', 'title': 'Water and potassium ion absorption by deuterium oxide resistant winter rye seedlings.', 's2_url': 'https://api.semanticscholar.org/CorpusID:37331579', 'source': 'S2ORC'}