Increasing interest in the stress physiology of higher plants has, in the last few years, greatly expanded our knowledge concerning the effects of stresses such as drought, freezing, nutrient deficiencies, disease and insect attack on plant metabolism. This work, however, has concentrated on the influences of stress on the basic processes of growth and development (primary metabolism). Very little attention has been paid to the changes in secondary metabolism that may be occurring. Information on the effects of stress conditions on secondary metabolites has come mainly from research efforts to maximize the yield of active constituents from herb, spice and drug plants and from attempts to reduce the levels of toxins in certain food and forage crops. Advances in our understanding of the functional roles of secondary metabolites in plants, however, and new information about how pest resistance is altered by stress should stimulate additional interest in the responses of secondary metabolites to stress.

Changes in the Levels of Plant Secondary Metabolites Under Water and Nutrient Stress

A chemical survey of 12 species of Umbelliferae in Tompkins County, New York, USA, revealed that species possessing furanocoumarins are most frequently found in open habitats: either swamps or thickets (Sium, Cicuta, Angelica spp.) or disturbed areas such as roadsides or old fields (Conium, Pastinaca, Heracleum spp.). Woodland species (Osmorhiza, Zizia spp.) character- istically lack furanocoumarins, though they may possess dihydrofuranocoumarin glycosides. Restric- tion of furanocoumarin production to plants in high-light environments is in keeping with the presumed mechanism of furanocoumarin phototoxicity towards insects, that is, ultraviolet-activated cross link- age of insect DNA. Cluster analysis of the insects on these umbellifers demonstrates that insect herbivores distribute themselves according to host furanocoumarin chemistry. By using a weighting factor that takes into consideration the differential discriminatory powers of specialists and generalists, it was possible to show that the insect faunae of plants containing angular furanocoumarins are more similar to each other than they are to the faunae of plants lacking angular furanocoumarins. The same case holds for the faunae of plants containing linear furanocoumarins, and for plants lacking furanocoumarins al- together. The chemical complexity of a plant species is reflected in the degree of dietary specialization of its insect associates; the more complex the furanocoumarin chemistry, as measured by the number and type of structures, the more specialized the feeding habits of the insects on the plant. Thus, plants lacking furanocoumarins have faunae dominated by generalists while plants with both linear and angular furanocoumarins have faunae dominated by extreme specialists. On the community level, then, it appears that furanocoumarin chemistry can account for patterns in distribution and abundance of insect herbivores on Umbelliferae.

Patterns of Furanocoumarin Distribution and Insect Herbivory in the Umbelliferae: Plant Chemistry and Community Structure

CHAPTER 7 – Intrinsic and Extrinsic Factors Affecting the Production of Secondary Plant Products

The volatile constituents of the aerial parts of Tanacetum balsamita have been examined by GC and GC/MS. Twenty-one components were detected, mainly monoterpenes, of which carvone (68%) was the major one.

Composition of the Essential Oil of Tanacetum balsamita L. ssp. balsamitoides (Schultz Bip.) Grierson from Iran

The amino acid compositions of three protein fractions obtained from broad bean leaves were estimated by ion exchange chromatography. Hydroxyproline was found present in the TCA-soluble, non-diffusible fraction and in the final residue after the further extraction with phenol-acetic acid-water (2: 1 : 1, w/v/v), but not in the extract itself. By comparison with the behaviour of four authentic isomers of hydroxyproline, under two standard conditions of chromatographic analysis, the isomer found was trans-4-hydroxy-proline. These results are discussed in relation to other reports of hydroxyproline occurring in plant material.

Fractionation of plant material II.—Amino acid composition of some fractions obtained from the broad bean plant (Vicia faba L.) and chromatographic differentiation of hydroxyproline isomers

Nitrates, nitrites, ammonia, amides, amino acids, proteins, and alkaloids were determined in plants under all treatments as previously described. At low nitrogen supply, belladonna synthesized alkaloids preferentially over protein. At high levels more protein and soluble nitrogenous compounds accumulated in tissue while the alkaloid level was relatively low. There appeared to be no direct relation between alkaloid and protein. γ-Aminobutyric acid may be a precursor to the belladonna alkaloids based on amounts of each present.

Nitrogenous Constituents of Atropa belladonna L. Grown on Different Sources of Externally Supplied Nitrogen

A method is described for the determination of hydrastine in hydrastis. This method is based on the adsorption of the hydrastis alkaloids on Florisil columns. Hydrastine is selectively eluted with ammoniacal alcohol and determined by a spectrophotometric procedure.

Use of Selective Adsorption in the Analysis of Hydrastis

A Pharmacognostic Study of Chrysanthemum Balsamita L., var. Tanacetoides Boiss., Together with a study of its Volatile Oil*1

Growth and morphology were compared on plants furnished six levels of nitrate and three of ammonia in water culture. The production of dry weight with ammonia was significantly greater than with nitrate. Ratios of shoot/root and leaf/stem indicated that use of the nitrogen was very different at low vs. high levels, particularly with ammonia nitrogen.

Ralph F. Voigt

Papers

Nitrogenous Constituents of Atropa belladonna L. Grown on Different Sources of Externally Supplied Nitrogen

Use of Selective Adsorption in the Analysis of Hydrastis

A Pharmacognostic Study of Chrysanthemum Balsamita L., var. Tanacetoides Boiss., Together with a study of its Volatile Oil*1

Growth and Differentiation of Atropa belladonna L. as Affected by Different Sources of Nitrogen