Carotenogenesis inhibition by fluorochloridone [3-chloro-4-(chloromethyl)-1-[3-(trifluoromethyl)phenyl]-2-pyrrolidinone] (0, 0.09, 0.18, 0.36, 0.72, or 1.44 μ M ) was evaluated in wheat ( Triticum aestivum L. cv Stacy) grown in nutrient solution. Fresh and dry weights of shoots were decreased as fluorochloridone concentration increased. Farnesol and geranylgeraniol equivalents were increased at fluorochloridone concentrations >0.18 μ M . β-carotene concentrations were decreased by fluorochloridone >0.09 μ M . Phytoene was increased at 0.09 μ M fluorochloridone and decreased above and below that concentration. Phytofluence concentrations increased at fluorochloridone concentrations ≤0.18 μ M and decreased at greater concentrations. CDAA [2-chloro- N,N -di-2-propenylacetamide] (2.9 and 5.8 μ M ) reversed the fluorochloridone-induced carotenogenesis inhibition. Growth inhibitions by CDAA were increased by 0.09 and 0.18 μ M fluorochloridone. Implications in terpenoid metabolism were discussed.

Norflurazon (0, 0.2, 0.4, 0.83, 1.65, or 3.3 μ M incorporated into sand inhibited carotenogenesis in wheat ( Triticum aestivum L. cv Holley). EPTC (0, 0.16, 0.33, 0.66, or 1.32 μ M ) was applied concomitantly. EPTC (0.66 and 1.33 μ M ) induced a partial reverse of the norflurazon inhibition of carotenogenesis. This reversal was postulated as due to an increased concentration of available geranylgeranyl pyrophosphate for phytoene synthesis and to an increased synthesis of carotene, chlorophyll a (Chl a), and chlorophyll b (Chl b) in EPTC-treated wheat. The increased pigment content partially offset photooxidation of carotenoids, Chl a, and Chl b at high light intensities. Utilization of these factors may result in protection of crops grown in soils bearing norflurazon residues.

Norflurazon (0, 0.1, 0.2, 0.4, or 0.8 μM) was applied concomitantly with desmethyl norflurazon (DMN), dichloropyridazinone (DCP), or the wrong isomer (WI) of norflurazon (0, 0.1, 0.2, 0.4, 0.8, 1.6, or 3.3 μM) to wheat (Triticum aestivum L. cv. Holley) grown in sand. After 14 days, carotenogenesis was inhibited by norflurazon and the inhibition was partially reversed by DMN, DCP, and WI. These reversals were observed at norflurazon concentrations ≤250 ≤ ∼0.823 μM in the potting medium. Carotene contents in norflurazon (0.4 μM) + no isomer, DMN, WI, or DCP (3.3 μM) were 5.4, 40.7, 28.6, and 22.2%, respectively, of that present in the untreated control. Therefore, these materials might function as antidotes to soil residues of norflurazon. Partitioning of norflurazon and DMN among triolein (TG), phosphatidylcholine (PC), and water was attained via isopycnic centrifugation. Norflurazon was highly soluble in PC and accumulated in PC. DMN was not soluble in TG and was soluble in water and PC at a ratio of 0.5 Change in water solubility when norflurazon is demethylated to DMN may be the basis for lack of bleaching influence of DMN. DMN, DCP, and WI partially reversed norflurazon carotenogenesis inhibition in the concentration range of norflurazon associated with phytoene synthesis and the low range of norflurazon concentrations associated with phytoene desaturase.

In a cell-free gibberellin precursor biosynthetic enzyme system from etiolated, unruptured sorghum (Sorghum bicolor L. var G- 522DR) coleoptiles, relative (2-14C)-mevalonic acid (DBED salt) (MVA) incorporation into ent-kaur-16-ene (kaurene) was decreased by EPTC at 0.1, 1.0, and 10.0 uM (37%, 52%, and 85%, respectively). R-25788 alone did not modify relative incorporation of MVA into kaurene. Yet, when EPTC + R-25788 were utilized concomitantly the incorporation of MVA into kaurene was equivalent to the untreated system. Thus, R-25788 reversed the inhibition by EPTC of the cyclization of geranylgeranyl-pyrophosphate (GGPP) to kaurene. As a mode-of-action for EPTC, this inhibition would explain all of the morphological responses of plants to EPTC.

Total vegetative hydrocarbon composition of sicklepod (Cassia obtusifolia L.) changed with age and photoperiod. Leaf epicuticular hydrocarbon composition of sicklepod and coffee senna (Cassia occidentalis L.) were different in plants of equal age grown in 16-hr or 12–13-hr photoperiods. The major leaf epicuticular hydrocarbon constituent of sicklepod grown in a 16-hr photoperiod was an unsaturated C32 constituent with a molecular weight of 446 with subsidiary constituents at relative elution temperatures equivalent to C30 and C34 having 34·9, 8·7, and 6·8% respectively, of the total hydrocarbon content.