Jean H. Langenheim

Bio: Jean H. Langenheim is an academic researcher from University of California, Santa Cruz. The author has contributed to research in topics: Hymenaea & Copaifera. The author has an hindex of 27, co-authored 66 publications receiving 2894 citations. Previous affiliations of Jean H. Langenheim include University of California, Berkeley.

Higher plant terpenoids:a phytocentric overview of their ecological roles

Abstract: Characteristics of higher plant terpenoids that result in mediation of numerous kinds of ecological interactions are discussed as a framework for this Symposium on Chemical Ecology of Terpenoids. However, the role of terpenoid mixtures, either constitutive or induced, their intraspecific qualitative and quantitative compositional variation, and their dosage-dependent effects are emphasized in subsequent discussions. It is suggested that little previous attention to these characteristics may have contributed to terpenoids having been misrepresented in some chemical defense theories. Selected phytocentric examples of terpenoid interactions are presented: (1) defense against generalist and specialist insect and mammalian herbivores, (2) defense against insect-vectored fungi and potentially pathogenic endophytic fungi, (3) attraction of entomophages and pollinators, (4) allelopathic effects that inhibit seed germination and soil bacteria, and (5) interaction with reactive troposphere gases. The results are integrated by discussing how these terpenoids may be contributing factors in determining some properties of terrestrial plant communities and ecosystems. A terrestrial phytocentric approach is necessitated due to the magnitude and scope of terpenoid interactions. This presentation has a more broadly based ecological perspective than the several excellent recent reviews of the ecological chemistry of terpenoids.

The endophytic fungal community in leaves of a coastal redwood population-diversity and spatial patterns

Abstract: SUMMARY Leaf endophytic fungi were isolated from 1 to 12-yr-old leaves of mature trees and basal sprouts of coastal redwood [Sequoia sempervirens (D Don ex Lamb) Endl] in a redwood forest in Central California Almost all samples yielded at least one species The two most frequent species were Pleuroplaconema sp and Cryptosporiopsis abietina Petrak Among isolated taxa are endophytic generalists, species previously known as pathogens and a possible specialist Species composition in leaves of progressing age in single branches revealed a patchy pattern of leaf colonization without an obvious sequence of succession Changes in diversity and equitability in the endophytic community with leaf age are linked with differential distribution of some species in young versus old leaves and the increase in species richness in 4- and 5-yr-old leaves The endophytic communities from leaves of trees and sprouts were generally similar, but with important differences in species richness and in distribution of Pleuroplaconema sp and Pestalotiopsis funerea (Desm) Stey Principal component analysis based on endophytic frequency also indicated closeness of trees and sprouts as groups, but clearly separated each tree from its sprout Differential susceptibility between trees and sprouts to endophytic infection is suggested on the basis of their endophytic communities

Inhibition of Nitrosomonas europaea by monoterpenes from coastal redwood (Sequoia sempervirens) in whole-cell studies

Abstract: Inhibition by allelochemicals, including monoterpenes, has been suggested as a factor in the extremely low nitrification rates observed in coastal redwood forests. Similarities between the molecular structure of known nitrification inhibitors and some conifer monoterpenes have been suggested as one reason for the inhibition of autotrophic nitrifiers by conifer monoterpenes. The effect of monolerpenes on nitrification rate and growth of Nitrosomonas europaea was examined in whole-cell pure culture experiments using the five most abundant monoterpenes in coastal redwood needles. These are (in order of decreasing concentration in the needles) limonene, α-pinenc, sabinene, myrcene, and γ-terpinene. Four of the five compounds significantly inhibited growth of N. europaea in batch culture experiments. Short-term kinetic studies of the two most inhibitory monoterpenes, limonene and α-pinene, were performed on whole cells to evaluate the mode of interaction between these chemicals and nitrification rates. Inhibition constants (Ki) of limonene (38 μM) and α-pinene (95 μM) were determined. Lineweaver-Burk plots of nitrification in the presence of monoterpenes appear to fit a noncompetitive inhibition model; however, the mechanisms of inhibition may be more complex.

The dilemma of plants: To grow or defend.

Abstract: Physiological and ecological constraints play key roles in the evolution of plant growth patterns, especially in relation to defenses against herbivores. Phenotypic and life history theories are unified within the growth-differentiation balance (GDB) framework, forming an integrated system of theories explaining and predicting patterns of plant defense and competitive interactions in ecological and evolutionary time. Plant activity at the cellular level can be classified as growth (cell division and enlargement) of differentiation (chemical and morphological changes leading to cell maturation and specialization). The GDB hypothesis of plant defense is premised upon a physiological trade-off between growth and differentiation processes. The trade-off between growth and defense exists because secondary metabolism and structural reinforcement are physiologically constrained in dividing and enlarging cells, and because they divert resources from the production of new leaf area. Hence the dilemma of plants: Th...

Insect-plant biology

Abstract: Half of all insect species are dependent on living plant tissues, consuming about 10% of plant annual production in natural habitats and an even greater percentage in agricultural systems, despite sophisticated control measures. Plants are generally remarkably well-protected against insect attack, with the result that most insects are highly specialized feeders. The mechanisms underlying plant resistance to invading herbivores on the one side, and insect food specialization on the other, are the main subjects of this book. For insects these include food-plant selection and the complex sensory processes involved, with their implications for learning and nutritional physiology, as well as the endocrinological spects of life cycle synchronization with host plant phenology. In the case of plants exposed to insect herbivores, they include the activation of defence systems in order to minimize damage, as well as the emission of chemical signals that may attract natural enemies of the invading herbivores and maybe exploited by neighbouring plants that mount defences as well.

Herbivory and plant defenses in tropical forests

Abstract: ▪ Abstract In this review, we discuss the ecological and evolutionary consequences of plant-herbivore interactions in tropical forests. We note first that herbivory rates are higher in tropical forests than in temperate ones and that, in contrast to leaves in temperate forests, most of the damage to tropical leaves occurs when they are young and expanding. Leaves in dry tropical forests also suffer higher rates of damage than in wet forests, and damage is greater in the understory than in the canopy. Insect herbivores, which typically have a narrow host range in the tropics, cause most of the damage to leaves and have selected for a wide variety of chemical, developmental, and phenological defenses in plants. Pathogens are less studied but cause considerable damage and, along with insect herbivores, may contribute to the maintenance of tree diversity. Folivorous mammals do less damage than insects or pathogens but have evolved to cope with the high levels of plant defenses. Leaves in tropical forests are ...

The function of terpene natural products in the natural world.

Abstract: As the largest class of natural products, terpenes have a variety of roles in mediating antagonistic and beneficial interactions among organisms. They defend many species of plants, animals and microorganisms against predators, pathogens and competitors, and they are involved in conveying messages to conspecifics and mutualists regarding the presence of food, mates and enemies. Despite the diversity of terpenes known, it is striking how phylogenetically distant organisms have come to use similar structures for common purposes. New natural roles undoubtedly remain to be discovered for this large class of compounds, given that such a small percentage of terpenes has been investigated so far.

Ammonia-Oxidizing Bacteria: A Model for Molecular Microbial Ecology

Abstract: ▪ Abstract The eutrophication of many ecosystems in recent decades has led to an increased interest in the ecology of nitrogen transformation. Chemolitho-autotrophic ammonia-oxidizing bacteria are responsible for the rate-limiting step of nitrification in a wide variety of environments, making them important in the global cycling of nitrogen. These organisms are unique in their ability to use the conversion of ammonia to nitrite as their sole energy source. Because of the importance of this functional group of bacteria, understanding of their ecology and physiology has become a subject of intense research over recent years. The monophyletic nature of these bacteria in terrestrial environments has facilitated molecular biological approaches in studying their ecology, and progress in this field has been rapid. The ammonia-oxidizing bacteria of the β-subclass Proteobacteria have become somewhat of a model system within molecular microbial ecology, and this chapter reviews recent progress in our knowledge of ...