The influence of Cycocel on the responses of wheat plants to water limitations
Considerable research has been concentrated on the foliage application of Cycoce, whereas little attention has focused on its use in seed application. Imbibition of caryopses of wheat (Triticum aestivum L.) in (2-chloroethyl) trimethylammonium chloride (Cycocel/CCC) resulted in a reduction in germination rate and a stunting of seedling growth. This was consistent with the appearance of a thicker stem, with shorter leaves than the control. Chlorophyll content per unit weight of leaf and numbers of tillers initiated both increased in comparison to controls. However, Cycocel treatment was accompanied by an enhanced survival capacity of seedlings when they were subjected to water limitation under growth room conditions. Seedlings grown from caryopses imbibed in 0.4 % Cycocel and exposed to a 7-day cycle of watering remained green and turgid beyond the time when the controls had wilted and died. Seedlings, at the fourth leaf stage, showed no wilting 23 days after watering had been withheld totally. Enhanced survival was also noted in seedlings when caryopses had been imbibed in Cycocel for 24 hours followed by a period of dry storage for up to 2 weeks prior to sowing. Enhanced survival was also detected as a carryover into the tillers, and the subsequent GEN2 seedlings, derived from GEN1plants. Cycocel pre-treatment did not alter Stomatal Index to an extent which could lead to enhanced water use efficiency, nor to the accumulation of proline to bring compatible solutes into equilibrium. However, the pre-treatment with Cycocel was found to enhance growth as a counter to water stress, and maintained fresh and dry weight of shoots when examined under the polyethylene glycol (PEG) induced stress. At the anatomical level the microscopic investigation of the GEN2 leaf tissues, derived from GENl plant, revealed a fully turgid cell structure, cells did not collapse and tissues were not distorted after the extraction of chlorophyll when compared with the control of the continuous watering as well as the moderate watering regime. Additionally, the cortex of GENl plants derived from pre-treated caryopses, showed a bright fluorescing unidentified deposition under Nutrient Solution (NS). This was more much greater when sampled from the NS + PEG treatments. From the results achieved Cycocel pre-treatment of caryopses appeared to have potential in manipulating wheat plants against water limitation. However, the mechanism (s) by which this can be achieved was not fully resolved in this study. Further investigations are required at the biochemistry and molecular level, particularly in relation to potential carryover effects between generations.