David E. Lincoln

Effect of light and temperature on monoterpenoid yield and composition in Satureja douglasii

Abstract Light intensity and day temperature were identified as principal modifying factors of monoterpenoid composition and yield in individuals of Satureja douglasii . The individuals represent compositional type and clinial patterns of infraspecific compositional variation. The lack of compositional interconversion confirms the tight genetic control of biosynthesis which results in these infraspecific patterns. There was marked influence by light intensity on monoterpenoid yield per leaf dry weight and by day temperature on yield per leaf. Low light intensity reduced leaf dry weight but had little effect on the amount of monoterpenoids per leaf whereas low day temperature increased both leaf weight and yield per leaf, compared to high light and day temperature effects. Day temperature modification of yield per leaf was related to modification of composition.

Implications of variation in resin composition among organs, tissues and populations in the tropical legume Hymenaea

Abstract Variation in leaf blade, petiole and primary stem resins, composed of sesquiterpene hydrocarbons, is analysed in two contrasting species of the tropical legume Hymenaea . Five populations of the New World H. courbaril , spanning a wide range of ecosystems, are compared with a population of the disjunct African H. verrucosa . Resins in petiole and primary stem tissue are similar, but differ significantly in total composition from leaf blade tissues. The major components, caryophyllene, α- and β-selinene and β-copaene vary most significantly among the tissues, but all compounds vary at highly significant levels among populations. The variation patterns in resin composition among the leaf blade and petiole/primary stem tissues are put into a larger context of comparison with the primarily diterpenoid patterns in secondary stem and pod tissues. Although the comparatively minor quantitative differences in the sesquiterpene systems could be attributed solely to developmental and physiological differences among the tissues and populations, the total weight of accumulating evidence regarding quantitative variation and demonstrated toxic and deterrent properties of sesquiterpene resins to insect herbivores leads us to hypothesize a possible role of differential predator pressures.

Variation of Satureja douglasii monoterpenoids in relation to light intensity and herbivory

Abstract Genotypic variation of monoterpenoid yield and composition in Satureja douglasii was shown by growth of clonal transplants under uniform conditions. Differentiation of monoterpenoid yield was correlated with light intensity and degree of herbivory along transects. High-yielding genotypes occurred under low light, high herbivory conditions, whereas low-yielding genotypes occurred in high light, low herbivory conditions. Differentiation of monoterpenoid composition was more weakly correlated with herbivory and light intensity than was yield. There was also some evidence for seasonal variations of yield.

The effect of moisture stress on monoterpenoid yield and composition in Satureja douglasii

Abstract The effect of moisture stress on monoterpenoid yield and composition of Satureja douglasii was studied under controlled conditions and in the field. Large differences in monoterpenoid yield observed among field populations were closely correlated with moisture stress. In greenhouse transplants grown under uniformly moist conditions these differences were significantly reduced. In all plants studied yield per leaf dry weight decreased with development. A growth chamber study using clones grown under different soil moisture regimes showed that high moisture stress reduced leaf weight and monoterpenoid yield per leaf, but had little effect on yield per leaf dry weight. Effects on monoterpenoid composition were less striking with high moisture stress causing a small decrease in the percentage of monoterpenoids with a p -menthane carbon skeleton and perhaps accelerating the rate of developmental conversions.

Palatability of monoterpenoid compositional types of Satureja douglasii to a generalist molluscan herbivore, Ariolimax dolichophallus

Abstract The differential palatability of monoterpenoid compositional types of Satureja douglasii to a native slug herbivore, Ariolimax dolichophallus, was determined. Types containing a high proportion of bicyclic monoterpenoids (camphene, camphor) were more palatable than those containing high proportions of p-menthane monoterpenoids (isomenthone, pulegone or carvone). In the case of individual monoterpenoids characteristic of these types, camphor proved to be most palatable and pulegone the least; carvone and isomenthone were intermediate. Differential herbivory on the compositional types was observed under field conditions. It is suggested that differential herbivory could have been important in determining the patterns of monoterpenoid variation and their distribution in S. douglasii.

Geographic patterns of monoterpenoid composition in Satureja douglasii

Abstract Monoterpenoid composition of mature leaves from populations distributed throughout the range of Satureja douglasii was determined by GLC. Five compositional types (I–V) were characterised, based on the high relative proportions of either carvone, pulegone, isomenthone, menthone or bicyclic compounds (camphenecamphor). These compositional types occured in restricted but overlapping portions of the species range. All samples contained camphene and camphor, amounts of which varied clinally along latitudinal gradient. Transplants were grown under greenhouse conditions. Although some populations exhibited significant environmental modification in amounts of principal constituents, the patterns of geographic variation were retained. Compositional types I–IV are based on compounds having ϱ-menthane structures and relationships among them are consistent with single gene actions within a common biosynthetic pathway. Using the dominant components of the collection site vegetation as an indication of habitat conditions, correlation of the genetically-determined compositional variation with environmental conditions was attempted. The distribution of the compositional types was partially isolated in this manner. Environmental factors which might be controlling the genetically-determined variation are discussed.

Vegetative Response to Photoperiod in the Tropical Leguminous Tree Hymenaea courbaril L

Hymenaea courbaril, a widely distributed tropical leguminous tree, was used in two experiments to compare the effects of photoperiod on vegetative growth and leaf resin chemistry and to examine the role of photoperiod in ecotypic differentiation. Seedlings grown from seeds collected in five different populations which span the latitudinal range of the tropics were used in both experiments. In experiment 1, using natural light in the greenhouse, seedlings grown for one year under tong photoperiod treatments (LP) had an average stem length twice that of seedlings grown under an eight-hour photoperiod treatment (SP). In experiment 2, seedlings were grown under four photoperiods of nine hours of daylight in the greenhouse plus 50 ft-c light extensions. Average total stem lengths were nearly identical for plants in all treatments. In LP plants growth nearly ceased during the winter but resumed in the spring. A LP/SP ratio based on average stem length for each population was correlated with latitude of seed origin suggesting ecotypic differentiation. Leaf resin composition was unaffected by photoperiod. Ecological implications of these responses are discussed. Also because the importance of photoperiodism in tropical plants generally has tended to be dismissed in reviews and textbooks, a literature review emphasizing physiological mechanisms of response and ecological roles under tropical conditions is inctuded. STUDY OF THE TROPICAL LEGUMINOUS GENUS H3menaea (subfamily Caesalpinioideae) was initiated in our laboratory from a survey of resin-producing plan.ts through geologic time which showed that copious production of these compounds occurred predominantly in subtropical and tropical environments (Langenheim 1969, 1972, 1975). Because most of the current knowledge of resin-producing plants was from tem.perate-zone conifers, Hymenaea was selected as an example of a tropical angiosperm genus for an intensive ecological and evolutionary investigation of resin synthesis. This amphi-Atlantic genus, which includes 14 species (Lee and Langenheim 1975), seemed a highly appropriate choice because the Leguminosae are one of the most important resin-producing families and the subfamily Caesalpinioideae contains some of the most prominent components of New World and African rain-forest ecosystems (Langenheim 1973). Furthermore, it was evolutionarily interesting because of the occurrence of New World Hymenaea resins (am.ber) from the Tertiary epoch (Langenheim 1963, 1969) and ecologically because the species have radiated throughout the major tropical lowland ecosystems. One species, H. courbaril, has a remarkable distribution, not only essentially coincident with the New World distribution of the genus, but also occurring across the same range of ecosystems (fig. 1 ). Its occurrence in such a wide variety of habitats and considerable morphological and chemical variation led to the postulation of ecotype differentiation with respect to several environmental factors. Photoperiod is one factor in the physical environmen,t to which a widespread and variable species such as H. courbaril might become differentiated. Likewise, variation in resin chemistry between local populations led to consideration of possible ecological significance of this variation. Therefore, a comparative study of the effects of photoperiod on vegetative growth and resin chemistry of populations of H. courbaril was designed, and results emphasizing the chemical experiments have been reported previously (StLbblebine, Langenheim, and Lincoln 1976). In our collaborative work with Dr. Harry Borthwick, a pioneer authority on plant photoperiodism, we becaine aware of the importance of photoperiodism in tropical plants being generally dismissed in textbooks and reviews by many plant physiologists (Pauly 1958, Vaartaja 1959, Salisbury 1963, 1965, Salisbury and Ross 1969, Steward 1968, Mohr 1972, Meyer et al. 1973, Leopold and Kriedermann 1975); however, with notable exceptions (McClelland 1924, Avim 1964, Longman 1969, Longman and Jenik 1974). Also relatively few ecologists have pointed out its potential significance (see Daubenmire 1974: 233), and none of the above reviews or textbooks emphasizes the relationships between the physiological mechanisms of plant photoperiodism and the possible roles these responses have in tropical ecosystems. Therefore, here we are reviewing somne of the literature concerning the concepts of photoperiodism in plants, the physiological mechanisms of these responses, and their ecological roles under tropical conditions. The results of our experiments with H. courbaril are discussed in this context. 18 BIOTROPICA 10(1): 18-29 1978 This content downloaded from 207.46.13.14 on Sat, 16 Apr 2016 04:35:55 UTC All use subject to http://about.jstor.org/terms

Vegetative growth and leaf resin composition in Hymenaea courbaril under photoperiodic extremes

Abstract Seedlings from five geographic populations of the widespread Hymenaea courbaril were grown for one year under two extremes of photoperiod. The short photoperiod treatment consisted of 8 hr of unsupplemented greenhouse daylight and the long photoperiod treatment of greenhouse daylight at the natural photoperiod of Santa Cruz, California (37° N) plus a 3-hr night interruption (0.25 mW/cm 2 ). Growth was measured by total stem length and leaf resin sesquiterpene composition was quantitatively analyzed by GLC. Photoperiod had no significant effect on leaf resin chemistry but the longer photoperiod markedly promoted vegetative growth. Large population differences in overall vegetative growth and quantitative leaf resin composition were also evident. Growth patterns indicated that the low intensity night break had little or no effect on growth.

Preliminary studies of monoterpenoid variability in Satureja douglasii

Abstract Monoterpenoid composition of samples from 10 populations of Satureja douglasii in a 250-ha area were analyzed in Spring 1974. Two distinct compositional types were found: Type A contained large amounts of limonene and carvone but very small quantites of piperitenone, piperitone, pulegone and isomenthone (3-oxy compounds), whereas Type B was essentially the reverse. This variation is attributed to a genotypic difference. The amounts of 3-oxy compounds varied greatly among the Type B populations. Increasing shade conditions were correlated with increased amounts of the more reduced compounds isomenthone and piperitone. Clonal lines were established from two Type B populations whose habitats represented extremes of sun and shade conditions. The two clonal lines, which had very different compositions in the field, produced similar oils under controlled conditions. Growth under different temperature regimes had little effect on composition. Developmental changes in composition implied the precursor-product relationships piperitenone→piperitone and pulegone→isomenthone. The data suggest that S douglasii monoterpenoid compositional patterns are significantly influenced by genetic and environmental factors (probably light intensity) as well as developmental processes.