Effect of variation in ear temperature on gibberellin content of wheat ears

When the ears of wheat were grown after anthesis at temperatures different from the rest of the plant the gibberellin content of the ears increased more rapidly at higher ear temperatures, whilst the plant temperature had little effect. This greater rate of gibberellin accumulation was associated with a greater rate of ear dry weight increase. Wheat ears detached from the plant increased their gibberellin content over 4 days when provided with sucrose and ewfkaurene.     

The Adaptation of Dunaliella to Widely-Differing Salt Concentrations

Methods are described for adapting pure cell-lines of Dunaliella,a green unicellular alga, to grow at concentrations between0.5 M and 3.5 M NaCl. It is shown that, provided large abruptchanges are avoided, cells of the same cell-line can becomeadapted to grow over this wide range of salt concentration.Once adapted, cultures are able to continue growing at a steadyrate for many generations provided that the salt concentrationremains constant. Viability tests performed after abrupt changesin salt concentration have shown that survival is higher afterdownward than after upward changes (3.5 M to 0.5 M NaCl: 20%;0.5 M to 3.5 M NaCl: 0.01% in D. parva 19/9). When the changein concentration from 0.5 M to 3.5 M NaCl takes place over aperiod of 48 h viability approaches 100%. The time needed for100% survival for a downward change over the same range is only1.5 h. There is no evidence for a genetic difference betweencell-lines adapted to particular concentrations of salt andit is concluded that the so-called ‘halophilic’and ‘halotolerant’ strains are interchangeable.It seems likely that the difference between the two types isa matter of gene expression. Key words: Dunaliella, salt concentration, viability