Physiological and growth responses of Centaurea maculosa (Asteraceae) to root herbivory under varying levels of interspecific plant competition and soil nitrogen availability

Summary Centaurea maculosa seedlings were grown in pots to study the effects of root herbivory by Agapeta zoegana L. (Lep.: Cochylidae) and Cyphocleonus achates Fahr. (Col.: Curculionidae), grass competition and nitrogen shortage (each present or absent), using a full factorial design. The aims of the study were to analyse the impact of root herbivory on plant growth, resource allocation and physiological processes, and to test if these plant responses to herbivory were influenced by plant competition and nitrogen availability. The two root herbivores differed markedly in their impact on plant growth. While feeding by the moth A. zoegana in the root cortex had no effect on shoot and root mass, feeding by the weevil C. achates in the central vascular tissue greatly reduced shoot mass, but not root mass, leading to a reduced shoot/root ratio. The absence of significant effects of the two herbivores on root biomass, despite considerable consumption, indicates that compensatory root growth occurred. Competition with grass affected plant growth more than herbivory and nutrient status, resulting in reduced shoot and root growth, and number of leaves. Nitrogen shortage did not affect plant growth directly but greatly influenced the compensatory capacity of Centaurea maculosa to root herbivory. Under high nitrogen conditions, shoot biomass of plants infested by the weevil was reduced by 30% compared with uninfested plants. However, under poor nitrogen conditions a 63% reduction was observed compared with corresponding controls. Root herbivory was the most important stress factor affecting plant physiology. Besides a relative increase in biomass allocation to the roots, infested plants also showed a significant increase in nitrogen concentration in the roots and a concomitant reduction in leaf nitrogen concentration, reflecting a redirection of the nitrogen to the stronger sink. The level of fructans was greatly reduced in the roots after herbivore feeding. This is thought to be a consequence of their mobilisation to support compensatory root growth. A preliminary model linking the effects of these root herbivores to the physiological processes of C. maculosa is presented.     

Sources of variation in rapidly inducible responses to leaf damage in the mountain birch-insect herbivore system

Summary Studies on rapidly inducible resistance in trees against insect herbivores show substantial variation in the strength of responses. Here we report the results of a study which examined causes of this variation. We bioassayed the quality of leaves of two developmental phases (young vs. mature) of the mountain birch Betula pubescens ssp. tortuosa by measuring the growth of two instars of Epirrita autumnata larvae. We used only short shoot leaves from trees of a natural stand, uniform in size and age. Damage was caused by larvae and artificial tearing of leaf lamina, varying the scale and time. We separated seasonal changes in plants from instar-dependent effects of the animals by testing experimental larvae in two subsequent growth trials. We found that only larval-made damage induced responses in leaves that made the leaves significantly poorer quality for the test larvae. Artificial damage induced only weak responses, and artificial canopy-wide damage even caused slight improvement of leaf quality. Cumulative leaf damage did not strengthen birch responses. Leaves that were in the expansion phase responded to damage while fully-expanded, mature leaves showed no response. The pattern of responses indicated that there might be physiological constraints: small-scale damage induced resistance against the larvae but largescale damage did not. Prevalent weather conditions might have modified these responses. Larvae of two instars and sexes, of low- and high-density populations responded to leaf damage similarly. However, prior experience of larvae with the host plant may have affected subsequent larval performance. Variation in rapidly inducible responses in birches was caused by plant characters rather than by test animals.     

Host fruit chemical stimuli eliciting distinct ovipositional responses from sibling species of Rhagoletis fruit flies

Laboratory experiments tested whether two economically-important sibling species of tephritid fruit flies have evolved distinct egg-laying responses to chemical stimuli on the fruits of their respective hostplants. The egg-laying preferences displayed by apple maggot flies, R. pomonella, and blueberry maggot flies, R. mendax, on artificial fruits treated with apple and blueberry extract paralleled their egg-laying responses to whole apples and blueberries. R. pomonella flies laid more eggs than R. mendax flies in artificial fruits treated with extract from ripe McIntosh apples, and vice versa for artificial fruits treated with extract from ripe Bluehaven blueberries. Furthermore, both species laid more eggs in artificial fruits treated with extract from their respective host fruits than control artificial fruits which were not treated with fruit extract. Prior electroantennogram recordings from R. mendax and R. pomonella flies exposed to volatiles from pentane extracts of apples and blueberries indicate that the antennal sensitivity of both species is selectively tuned to their respective host fruit odors. This differentiation in their olfactory responses to fruit odors could be important in mediating their distinct ovipositional responses to blueberry and apple fruits. Extract from unripe McIntosh apples also elicited egg laying by R. pomonella flies, however, artificial fruits treated with unripe apple extract received 1.9 times fewer eggs than those treated with ripe apple extract. Moreover, the numbers of R. pomonella ovipositor punctures and eggs placed in wax artificial fruits were increased when the artificial fruits were treated with a blend of 7 identified apple esters. Black coloration on these artificial fruits and the presence of apple esters had a synergistic effect on the egg-laying behavior of R. pomonella flies, which caused them to lay substantially more eggs per black fruit than white fruit treated with the same concentration of apple esters. In summary, our results indicate that the egg-laying responses of R. pomonella flies are mediated by the integration of information from fruit chemical and visual cues, and that R. mendax and R. pomonella flies have evolved divergent egg-laying responses to chemical stimuli on the fruits of their respective hostplants. These findings are discussed in the context of other studies on plant compounds which influence the ovipositional behavior of phytophagous Diptera.

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Stimuli chimiques des pommes et des myrtilles induisant la ponte des espèces jumelles, Rhagoletis pomonella et R. mendax

Résumé Des fruits artificiels en cire traités avec des extraits de fruits ont provoqué chez les espèces jumelles de R. mendax (Curran) et R. pomonella (Walsh) des réactions de ponte différentes suivant les stimulations chimiques par les fruits. Le comportement de ponte sur des fruits artificiels traités avec des extraits au pentane des myrtilles mûres (Vaccinium corymbosum L.) et de pommes mûres (Malus pumila Miller = Pyrus malus L.), est le même que sur des fruits naturels, ce qui montre que la réponse aux stimulations chimiques provenant du fruit constitue un aspect important de la reconnaissance de l'hôte. R. pomonella pond plus d'ufs que R. mendax sur les fruits artificiels traités à l'extrait de pommes mûres; c'est l'inverse pour les fruits traités aux extraits de myrtille. Les fruits artificiels traités avec des pommes ou des myrtilles provoquent la ponte de R. pomonella, tandis que les myrtilles mûres seules provoquent la ponte de R. mendax. Les extraits de pommes vertes stimulent la ponte de R. pomonella mais elle est alors 2 fois plus faible qu'avec des extraits de pommes mûres. Un mélange de 7 esters identifiés dans l'extrait de pomme induit aussi la ponte de R. pomonella. Le nombre de piqûres de tarièresfli dans les fruits artificiels en cire et le nombre d'ufs par fruit ont été augmentés par addition d'esters de pommes à des fruits blancs ou noirs. La couleur des fruits artificiels influence aussi la réaction de ponte de R. pomonella; la fréquence des piqûres de tarière contenant un uf et le nombre d'ufs par fruit étaient significativement plus élevés sur les fruits noirs que sur les fruits blancs traités avec la même concentration d'esters de pomme. Les fruits artificiels noirs traités avec la concentration la plus stimulante d'esters de pommes ont reçu 2, 3 fois plus d'ufs que les fruits blancs avec les mêmes concentrations en esters. Ces résultats montrent que les esters de pomme et la couleur noire stimulent synergiquement la ponte de R. pomonella sur des fruits artificiels.

     

Structural damage to oak leaves alters natural enemy attack on a leafminer

A field experiment was conducted to test the role of structural changes in oak leaves caused by folivory on natural enemy attack of leafmining larvae and pupae of Cameraria sp. nov., while controlling for induced chemical responses. Damaged and intact leaves of Quercus emoryi were sealed with a fluorocarbon telomer in 1988–1989 to prevent release of long-range or contact chemical cues that might be perceived by searching parasitoids and predators. These leaves were attached to Q. emoryi leaves harboring first instars of Cameraria, but otherwise were undamaged. Rates of attack by natural enemies of leafminers in leaves with sealed, damaged leaves attached were significantly greater than those in control leaves, indicating that structural damage alone influences attack by natural enemies. Survival of leafminers in leaves with attached damaged leaves was significantly less than that of controls, suggesting that structural changes in leaves due to folivore feeding affect population dynamics of Cameraria via increased attack by the third trophic level.

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Résumé Des expériences ont été faites dans la nature pour évaluer l'influence des modifications structurales provoquées par la défoliation sur les attaques des ennemis naturels des chenilles mineuses et des chrysalides de Cameraria sp. nov. En 1988–89 des feuilles saines et endommagées de Quercus emoryi ont été enduites de télomère de fluorocarbone pour empêcher l'émission d'indicateurs chimiques à distance ou de contact pouvant être utilisés par les parasitoïdes et les prédateurs lors de leur prospection. Ces feuilles ont été attachées à des feuilles apparemment intactes de Q. emoryi mais hébergeant des Cameraria du premier stade. Les attaques par les ennemis naturels des mineuses étaient plus importantes sur feuilles associées à des feuilles endommagées mais enduites de fluorocarbone que sur feuilles témoins, ce qui montre que les dégâts structuraux seuls influent sur les attaques par les ennemis naturels. La survie des mineuses dans les feuilles associées à des feuilles endommagées était plus faible que chez les témoins, ce qui suggère des changements structuraux dans les feuilles provoqués par les phytophages affectant la dynamique de population de Cameraria via une attaque accrue par le troisième niveau trophique.

     

Correlated responses of growth traits to selection for high and low plasma alkaline phosphatase in mice

Summary The effectiveness of two way selection for plasma alkaline phosphatase (ALP) was investigated in order to determine its influences on growth traits through thirteen generations. The responses of the two lines selected for high (HP) and low (LP) ALP at 45 days of age were compared to that of the mice selected for large (L) and small (SM) body size. The selection responses of plasma ALP were very effective for both HP and LP lines, with average responses per generation calculated from linear regressions of 0.227±0.037 and –0.088±0.022 respectively. The final levels of ALP in HP and LP were 5.54±0.71 and 1.27±0.20 in the thirtheenth generation, while the SM, L and base population had levels of 3.49±0.08, 0.86±0.55 and 2.77±0.56 respectively. The body weight at 45 days of age in LP (31.4±1.4 g) as a correlated response was significantly higher than HP (23.4±1.8 g) at generation 10. The correlated response of milk yield, measured by weight gain up to 12 days of age, was significantly greater in the LP line than in HP, but the correlated response of gains after weaning was not so different as the response of milk yield. The response of litter size and weight in LP showed significant higher levels than that of HP, but pups' birth weight did not differ between LP and HP. It is suggested that the correlated response of milk yield contributed more to the divergence of body size between HP and LP than the gain after weaning.Realized heritabilities of ALP were 0.335±0.059 (HP) and 0.279±0.051 (LP). Realized genetic correlations between ALP and 45 days' body weight were –0.27±0.13 (HP with SM) and –0.52±0.19 (LP with L). Realized genetic correlations between ALP and milk yield were –0.95±0.03 (HP) and –0.37±0.29 (LP). Correlations between ALP and postweaning gains were fairly low.     

Levels of indole-3-acetic acid in intact and decapitated coleoptiles as determined by a specific and highly sensitive solid-phase enzyme immunoassay

A specific solid-phase enzyme immunoassay for the detection of as little as 3–4 pg of indole-3-acetic acid (IAA) is described. The assay involves minimal procedural efforts and requires only standard laboratory equipment. Up to 50 samples in triplicate, processed simultaneously, can be assayed and evaluated in 2.5 h. As little as 1 mg oat coleoptile tissue is sufficient for a quantitative IAA analysis and little or no extract purification is necessary. Using this assay, levels of IAA have been determined in coleoptiles of maize and oat. The distribution of IAA within single coleoptiles was quantitated and the production of IAA during the regeneration of the physiological tip in Avena coleoptiles was investigated. The changes in levels of IAA and other major phytohormones were quantitated during the growth of oat coleoptiles.Abbreviations ABA abscisic acid - BHT butylated hydroxytoluene - BSA bovine serum albumin - IAA indole-3-acetic acid - TBS Trishydroxymethylaminomethane buffered saline Part 21 in the series Use of Immunoassay in Plant Science     

Lipoxygenase activity in apples in relation to storage and physiological disorders

Different methods for the preparation of active lipoxygenase (LOX) extracts from apples were compared. Highest activities were obtained using a 0.25 M phosphate buffer (pH 7) containing 1% Triton X-100 and 10^?2 M metabisulphite as extraction solvent. LOX activity during storage was investigated in the core, flesh, and peel. Activity was always highest in the core and peel. On storage, activity was increased in each part of the fruit but especially in the core and peel. Increase in LOX preceded the browning of the core. LOX may be responsible for the browning and may be concerned in the induction of superficial scald.     

Hypothalamic and hormonal control of the photoperiodically induced vernal functions in the White-crowned Sparrow,Zonotrichia leucophrys gambelii

To assess the role of the hypothalamo-hypophysial complex in the control of photoperiodically induced vernal premigratory responses in the White-crowned Sparrow, the effects of hypothalamic lesions and systemic administration of several hormones on these responses were investigated. Lesions that destroyed the posterior median eminence (PME) or the entire median eminence (ME) inhibited photoperiodically induced testicular growth, premigratory fattening and Zugunruhe. Lesions in the basal infundibular nucleus (IN) that resulted in complete inhibition of testicular growth abolished Zugunruhe, but allowed varying degrees of fattening. The systemic administration of prolactin, testosterone propionate (TP) or the combination thereof in the PME-lesioned birds induced fattening similar to that observed in photostimulated controls but did not induce Zugunruhe. It is concluded that testosterone and prolactin are the most important hormones involved in the control of vernal premigratory fattening. The role of these hormones in the induction of vernal Zugunruhe is not positively proven.     

Environmental history and physiological state influence feeding responses of Atrina zelandica to suspended sediment concentrations

Epifaunal suspension-feeding bivalves can play important roles in marine ecosystems affecting macrobenthic communities, benthic boundary layers and benthic-pelagic coupling, not just by their presence but also by any changes in feeding behaviour. While seston quality and quantity have consistently been found to be important influences on the feeding rates of suspension-feeding bivalves, factors stressing individuals are also likely to be important, as they may affect energy-dependent thresholds of response. We postulated that (1) history of seston quantity would affect how suspension feeders deal with increases in total suspended particulates, and (2) high-seston concentrations would affect feeding rates more in individuals whose energy reserves were low after spawning. Three sites were selected for short-term (1 day) feeding experiments on the pinnid bivalve, Atrina zelandica. At one site, the experiment was run pre-and postspawning. Atrina exhibited high rejection of filtered particles (mostly 75% to 100%) and high organic absorption efficiencies (0.9-1) at all seston levels. Strong differences in the response of feeding behaviour to increased seston concentrations were observed between A. zelandica from the different sites, with lesser differences observed between times. The site-specific feeding responses to seston concentrations observed are likely to affect our ability to model responses of A. zelandica to sediment loading and to influence the importance of A. zelandica to benthic-pelagic coupling.     

Physiological functions of Wilms’ tumor 1-associating protein and its role in tumourigenesis

The Wilms’ tumor-associated gene WT1 encodes a tumor suppressor gene, which is implicated in renal differentiation and development of adult urogenital system. Wilms’ tumor 1-associating protein (WTAP) is initially identified as a nuclear protein that specifically interacts with WT1 in both in vitro and in vivo assays. WTAP is ubiquitously expressed in different tissues and various growth periods, and its expression is involved in cell cycle, RNA splicing and stabilization, N6-methyladenosine RNA modification, cell proliferation, and apoptosis as well as embryonic development. In the present review, we aimed to summarize the functions of WTAP in various physiological and pathological processes, in particular with regard to the current knowledge about the role of WTAP in tumorigenesis of different cancers.