André Blouet

Morphological and anatomical modifications in winter barley culm after late plant growth regulator treatment

One of the major factors limiting yield production in barley (Hordeum vulgare L.) has been its poor straw strength. Consequently, a greater stiffness of the upper part of the culm was desirable. So, a late application of plant growth regulator could be interesting for weak-strawed barley cultivars. The objective of these experiments was to investigate the effect of a late application of a combination of chlormequat chloride (2-chloroethyl-trimethyl-ammonium chloride), ethephon (2-chloroethyl phosphonic acid) and imazaquin (2-[4-isopropyl-4-methyl-5-oxo-2-imidazolin-2-yl] nicotinic acid) on the morphological and anatomical characteristics of barley main stems. In a field trial and a greenhouse experiment, a foliar treatment was applied to a two-row winter barley (Labea) at growth stage 7 (Feekes, 1941). Measurements of plant height, internode lengths, dry weights and microscopic examination of cross-sections of the top three internodes were made at anthesis. The plant growth regulator (PGR) decreased significantly plant height by reducing the length of the upper internodes. The PGR did not modify the total weight of the upper internodes, but induced an increase of the dry weight per unit length of the main stem. The shortening of the internodes combined with the higher density of the tissues contributes to the stiffness of the stem. This was confirmed by anatomical studies which showed the modifications of the supporting tissues. The application of the plant growth regulator did not affect grain yield.

Contribution of the wheat (Triticum aestivum L.) flag leaf to grain yield in response to plant growth regulators

In West-Europe, intensive cereal management uses plant growth regulators (PGRs) especially for wheat. A green-house experiment compared the effects of two PGRs on flag leaf characteristics and yield of winter wheat. Chlormequat chloride + choline chloride (CCC) and chlormequat chloride + choline chloride + imazaquin (CCC+I) were applied to winter wheat at growth stage 5 (Feekes Large scale). CCC and CCC+I significantly increased flag leaf surface area at anthesis. Both treatments also enhanced chlorophyll content of the main stem flag leaf. The grain filling period was extended with PGR application by 2 days. CCC and CCC+I significantly increased net CO2 assimilation rates during the flag leaf life. No effects of PGR spraying were observed on the pattern of 14C labelled assimilate distribution. Increased grain yield was due to the increase in average grain weight. The results indicate that PGR treatments increased flag leaf contribution to grain filling. The addition of imazaquin (I) to chlormequat (CCC) improved the effects of CCC.

Effect of imazaquin on absorption, translocation, and pattern of distribution of chlormequat chloride in winter wheat

The role of imazaquin in the absorption, translocation, and distribution of chlormequat chloride in CYCOCEL* CL has been studied in winter wheat. Three treatments were applied to the 5th leaf of the main stem at growth stage 5 (Feekes Large scale): (1)14C-chlormequat chloride, (2) CYCOCEL* CL containing14C-chlormequat chloride, and (3) CYCOCEL* CL containing14C-imazaquin. Tracing of the radioactivity was followed in the treated leaf, main stem, tillers, and roots. Results showed that more than 85% of the radioactivity absorbed remained in the treated leaf. Ten days after the application of chlormequat chloride alone, 94.4% of the14C-chlormequat was found in the treated leaf, 2.9% in the main stem, 1.2% in the tillers, and 1.4% in the root system versus 88.2, 8.2, 2.1, and 1.4%, respectively, for the chlormequat chloride plus imazaquin treatment. It was concluded that imazaquin increases the mobility and the pattern of distribution of chlormequat chloride in the plant.

Hybrid wheat seed production potential using the chemical hybridizing agent SC2053

The success of hybrid wheat depends greatly on the female seed production. The objectives of this experiment were to evaluate the effects of two doses of a Chemical Hybridizing Agent (CHA) on the stigma receptivity. In a growth chamber, plants were hand emasculated or treated with a normal (D1) or an excessive dose (D2) of the CHA. Spikes were hand pollinated at different dates during the flowering period. The CHA did not affect significantly the female receptivity neither in duration nor in intensity. We pointed out that for the hybrid seed production there was an optimal period of 5 days. If pollination took place during this period, the seed set and the 1000 grain weight were the highest.