Stimulation of Plant Growth by (3-Methoxyphenyl)acetonitile Applied as a Foliar Spray In Vivo or as a Medium Amendment In Vitro

Meadowfoam (Limnanthes alba Hartweg ex. Benth.) seedmeal, a coproduct of oil extraction from meadowfoam seeds, has been found to increase the growth of greenhouse plants when added to the growing medium. (3-Methoxyphenyl)acetonitrile (3-MPAN) is a biologically active glucosinolate degradation compound previously identified at high levels in meadowfoam seedmeal. 3-MPAN was tested as a foliar spray at several concentrations (0 μm, 0.18 mm, 0.37 mm, 0.73 mm, 2.2 mm, and 7.3 mm) on lime basil (Ocimum basilicum L.), spearmint (Mentha spicata L.), cuphea (Cuphea lanceolata L.), and French marigold (Tagetes patula L.) seedlings grown in the greenhouse. 3-MPAN increased the fresh and dry weights of all four species tested. However, this effect was dose-dependent among species with spearmint growth higher at all 3-MPAN application rates, whereas basil growth was promoted at only the 2.2-mm rate. 3-MPAN increased the tissue concentrations of the secondary compound (−)-carvone at the 7.3-mm application rate. In addition, 3-MPAN added to sterile nutrient media stimulated the growth of spearmint plants in vitro. These results indicate that 3-MPAN may have applicability as a postemergent growth stimulant for a wide variety of plants.

Decarboxylation of malonyl-(acyl carrier protein) by 3-oxoacyl-(acyl carrier protein) synthases in plant fatty acid biosynthesis

In order to identify regulatory steps in fatty acid biosynthesis, the influence of intermediate 3-oxoacyl-(acyl carrier proteins) (3-oxoacyl-ACPs) and end-product acyl-ACPs of the fatty acid synthase reaction on the condensation reaction was investigated in vitro, using total fatty acid synthase preparations and purified 3-oxoacyl-ACP synthases (KASs; EC 2.3.1.41) from Cuphea lanceolata seeds. KAS I and II in the fatty acid synthase preparations were assayed for the elongation of octanoyl- and hexadecanoyl-ACP respectively, and the accumulation of the corresponding condensation product 3-oxoacyl-ACP was studied by modulating the content of the reducing equivalents NADH and NADPH. Complete omission of reducing equivalents resulted with either KAS in the abnormal synthesis of acetyl-ACP from malonyl-ACP by a decarboxylation reaction. Supplementation with NADPH or NADH, separately or in combination with recombinant 3-oxoacyl-ACP reductase (EC 1.1.1.100), led to a decrease in the amount of acetyl-ACP and a simultaneous increase in elongation products. This demonstrates that the accumulation of 3-oxoacyl-ACP inhibits the condensation reaction on the one hand, and induces the decarboxylation of malonyl-ACP on the other. By carrying out similar experiments with purified enzymes, this decarboxylation was attributed to the action of KAS. Our data point to a regulatory mechanism for the degradation of malonyl-ACP in plants which is activated by the accumulation of the fatty acid synthase intermediate 3-oxoacyl-ACP.

Cytogenetics off interpopulation Cuphea lanceolata hybrids

Cuphea lanceolata Ait. (Lythraceae) is an annual diploid (x = 6) with medium-chain fatty acid rich seed oils. Wild C. lanceolata populations are classified as C. lanceolata f. silenoides or C. lanceolata f. lanceolata on the basis of flower pigment differences. Although these taxa are taxonomically close, their interfertility has not been demonstrated. We describe meiotic phenomena underlying the sterility of hybrids between C. lanceolata f. silenoides (LNS-43) and C. lanceolata f. lanceolata (LNC-78) populations. We assayed metaphase and anaphase I microsporocytes of the parent and hybrid populations. The hybrids were female and male sterile. The mean percentage of stainable pollen was 94.9% for the parents and 1.1% for the hybrids. Chromosomes paired and disjoined normally in the parents (LNS-43 and LNC-78) and abnormally in the hybrids (LNS-43 × LNC-78 and LNC-78 × LNS-43). Univalents, unequal chromosome distributions, and laggards were observed in the hybrids. The mean number of univalents per cell was 0.00 for the parents and 5.95 for the hybrids, the mean number of bivalents per cell was 6.00 for the parents and 1.51 for the hybrids, and the mean number of chiasmata per cell was 9.19 for the parents and 4.04 for the hybrids. The most frequently observed (75%) anaphase I chromosome distribution for the hybrids was 7:5:0 (pole–pole–laggards). The genome affinities of the hybrids were half those of the parents (a mean of 0.5 for the hybrids as opposed to 1.0 for the parents). Although C. lanceolata f. silenoides and C. lanceolata f. lanceolata freely hybridize, their progeny are sterile, and the genetic diversity of LNC-78, and perhaps of C. lanceolata f. lanceolata as a whole, cannot be accessed through hybrids with C. lanceolata f. silenoides or C. viscosissima.Key words: Lythraceae, Cuphea, medium-chain fatty acids, interspecific hybrids, meiosis.