Phaseollin production in cell suspensions and whole plants of Phaseolus vulgaris

Production of phaseollin was measured in cell suspension cultures and whole plants of Phaseolus vulgaris. In suspension cultures phaseollin appeared when there was no further increase in cell mass. Cells transferred to a medium without auxins yielded three times higher phaseollin concentrations than cells grown in their presence. Addition of autoclaved fungal mycelia or polysaccharides as elicitors resulted in an increased phaseollin concentration in the cell suspension.In whole plants phaseollin could be detected only after the plants were challenged by a fungus which caused lesions (browning) of the upper root neck region, Rhizoctonia solani. Treatment of non-infected plants with autoclaved fungal mycelia or other elicitors did not induce phaseollin production. However, when they were added before or together with the pathogenic fungus, the elicitors further increased phaseollin concentration in the root neck regions of the plants. This indicated that the pathogenic fungus was important for the penetration of the elicitors to inner plant tissues where phaseollin (and probably other phytoalexins) is produced.     

Induction of H2O2 and related enzymes in tomato roots infected with root knot nematode (M. javanica) by several chemical and microbial elicitors

The effects of chemical and microbial elicitors such as β-aminobutyric acid (BABA), Salicylic acid (SA), and Pseudomonas fluorecens CHAO on hydrogen peroxide generation and activity of the enzymes related to its metabolism, i.e., superoxide dismutase (SOD), guaiacol peroxidase (GPOX), and catalase (CAT) were investigated in tomato roots infected with root-knot nematode (Meloidogyne javanica). Results of this study show that treating the tomato seedlings with the above elicitors significantly reduces the nematode infection level. Among the tested elicitors, BABA has reduced the nematode galls, number of egg masses per plant and number of eggs per individual egg mass more than the others. Additionally, the amount of H₂O₂, a product of oxidative stress, SOD and GPOX specific activities were significantly increased in the elicitor treated plants in comparison to control. Our observation shows that BABA also increases the H₂O₂ accumulation and the SOD and GPOX activities more as compared with the other tested elicitors. Such increases have occurred in two phases and maximum levels of them were observed at 5 days after treatment. In contrast with the increase in SOD and GPOX activities, the CAT activity doesnot show any significant increase in treated plants as compared with the control and other tested elicitors. It can be concluded that BABA, SA, and Pseudomonas fluorescens CHAO induce oxidative stress in tomato roots through generation of reactive oxygen species (ROS) and the enzymes related to their metabolism.     

Biotechnological approaches for field applications of chitooligosaccharides (COS) to induce innate immunity in plants

Plants have evolved mechanisms to recognize a wide range of pathogen-derived molecules and to express induced resistance against pathogen attack. Exploitation of induced resistance, by application of novel bioactive elicitors, is an attractive alternative for crop protection. Chitooligosaccharide (COS) elicitors, released during plant fungal interactions, induce plant defenses upon recognition. Detailed analyses of structure/function relationships of bioactive chitosans as well as recent progress towards understanding the mechanism of COS sensing in plants through the identification and characterization of their cognate receptors have generated fresh impetus for approaches that would induce innate immunity in plants. These progresses combined with the application of chitin/chitosan/COS in disease management are reviewed here. In considering the field application of COS, however, efficient and large-scale production of desired COS is a challenging task. The available methods, including chemical or enzymatic hydrolysis and chemical or biotechnological synthesis to produce COS, are also reviewed.     

Induced systemic resistance in groundnut by foliar application of Headline (Pyraclostrobin 20% WG)

Plant’s own defence mechanisms can be stimulated by the application of elicitors for its protection. We evaluated the ability of Headline (Pyraclostrobin 20% WG) to induce systemic resistance in 40-day-old field-grown groundnut plants by foliar application. Elevated levels of defence-related enzymes such as phenylalanine ammonia lyase, peroxidase, β 1,3 glucanase, nitrate and nitrite reductase and other biochemical parameters such as total phenol, total protein, total carbohydrate and total chlorophyll content were found highest in Headline treated plants on fourth day after treatment in comparison with untreated plants. The treated plants showed enhanced growth and development as well as increased yield up to 16%. About 10% mortality rate was found in groundnut seeds treated with Headline when grown on Sclerotium rolfsii-infested soil than control. These results indicate that foliar application of Headline can be successfully developed the broad-spectrum resistance against pathogens in groundnut.     

Nicotiana tabacum agglutinin expression in response to different biotic challengers

The induction of the Nicotiana tabacum agglutinin or NICTABA was studied in tobacco leaves infected with a necrotrophic pathogen (Botrytis cinerea) and compared to folivory by several pest arthropods. It was clearly demonstrated that B. cinerea does not induce NICTABA expression, while arthropod herbivory stimulates a strong NICTABA accumulation. In order to further investigate the importance of feeding style for inducing lectin expression, tobacco plants were challenged with several arthropods that use different feeding guilds. It was shown that chewing caterpillars (Spodoptera littoralis and Manduca sexta) and cell-content-feeding spider mites (Tetranychus urticae) induce NICTABA expression, while infestation with phloem-feeding herbivores such as aphids and whiteflies (Myzus nicotianae and Trialeurodes vaporariorum) does not result in NICTABA accumulation. The presence of elicitors for NICTABA induction in oral secretions, salivary extracts or excrement extracts from S. littoralis larvae, was investigated through repeated application of different secretions to punctured wounds and analysis of lectin expression. However, none of the treatments could induce the accumulation of NICTABA as did herbivory.     

Characterization of the Mamestra configurata (Lepidoptera: Noctuidae) larval midgut protease complement and adaptation to feeding on artificial diet,Brassica species,and protease inhibitor

The midgut protease profiles from 5th instar Mamestra configurata larvae fed various diets (standard artificial diet, low protein diet, low protein diet with soybean trypsin inhibitor [SBTI], or Brassica napus) were characterized by one‐dimensional enzymography in gelatin gels. The gut protease profile of larvae fed B. napus possessed protease activities of molecular masses of approximately 33 and 55 kDa, which were not present in the guts of larvae fed artificial diet. Similarly, larvae fed artificial diet had protease activities of molecular masses of approximately 21, 30, and 100 kDa that were absent in larvae fed B. napus. Protease profiles changed within 12 to 24 h after switching larvae from artificial diet to plant diet and vice versa. The gut protease profiles from larvae fed various other brassicaceous species and lines having different secondary metabolite profiles did not differ despite significant differences in larval growth rates on the different host plants. Genes encoding putative digestive proteolytic enzymes, including four carboxypeptidases, five aminopeptidases, and 48 serine proteases, were identified in cDNA libraries from 4th instar M. configurata midgut tissue. Many of the protease‐encoding genes were expressed at similar levels on all diets; however, three chymoptrypsin‐like genes (McSP23, McSP27, and McSP37) were expressed at much higher levels on standard artificial diet and diet containing SBTI as was the trypsin‐like gene McSP34. The expression of the trypsin‐like gene McSP50 was highest on B. napus. The adaptation of M. configurata digestive biochemistry to different diets is discussed in the context of the flexibility of polyphagous insects to changing diet sources. Published 2010 Wiley Periodicals, Inc.     

Induction of systemic acquired resistance in Zea mays L. by Aspergillus flavus and A. parasiticus derived elicitors

Host defence mechanisms can be elicited by using different elicitors produced from the pathogen/host. In this study, an effort has been made to study the effect of two fungal elicitors derived from Aspergillus flavus and A. parasiticus on induction of various defence-related enzymes in maize (Zea mays L.). Foliar application was done on 20-days-old maize plant with 10% A. flavus fungal culture filtrate (AFFCF) and A. parasiticus fungal culture filtrate (APFCF) as elicitors to trigger systemic acquired resistance (SAR). As a response of SAR, an increase in activities of phenylalanine ammonia lyase (PAL), peroxidase (POX), β-1,3-glucanase, nitrate reductase (NR) and nitrite reductase (NiR), total proteins were found highest on 4th day after treatment (DAT), whereas total carbohydrate and total chlorophyll on 2nd and 6th DAT, respectively, in comparison with the control plants. The SDS PAGE analysis revealed the induction of PR proteins, namely Chitinase (25, 29?kDa) and β-1,3-glucanase (33?kDa), in treated plants in comparison with untreated control plants. The treated plants showed enhanced growth and development as well as increase in yield. About 100% survival rate was found in maize seeds treated with AFFCF and APFCF and grown on respective fungal infested soil than control. The enhanced activities of defence enzymes and elevated protein, carbohydrate, chlorophyll content in treated maize plants suggest the induction of SAR against A. flavus and A. parasiticus by using the same fungal elicitors.     

Development of probiotic diets for the olive fly: evaluation of their effects on fly longevity and fecundity

One possible control strategy against the olive fly, Bactrocera oleae, the most serious olive crop pest, is the Sterile Insect Technique (SIT) application. However, a number of problems associated with this method remain that decrease the effectiveness of SIT, including the quality of reared insects. Taking the importance of the relationship between the olive fly and bacteria into consideration, the effects of probiotic diets enriched with Pseudomonas putida on B. oleae longevity and fecundity were evaluated. First, we found that the probiotic bacterium, P. putida, is conveyed from diets to the oesophageal bulb as well as to the fly midgut after feeding on the probiotic diet. Subsequently, B. oleae adults fed on either: (a) a standard full protein and sugar diet; (b) a sugar only diet; (c) a probiotic standard full protein and sugar diet; or (d) a probiotic sugar diet. Flies fed on probiotic diets were supplied with an inoculated gel containing P. putida; non‐inoculated gel was provided to the flies fed on non‐probiotic diets. B. oleae males and females that fed on sugar diets did not survive as long as those that fed on protein diets. A comparison of the longevity of adults fed on full diet and sugar with their respective probiotic diets revealed no significant difference. Males fed on the sugar only diet survived longer than males fed on probiotic sugar diet, and females fed on the full protein and sugar diet survived much longer than females fed on the full probiotic diet. As regarding fecundity, both full diets resulted in a higher number of eggs laid per female. Females fed on the probiotic sugar diet laid a higher number of eggs than females that fed on sugar only. The inoculated gel of the probiotic sugar diet contained a significantly higher quantity of leucine, isoleucine and proline than the non‐inoculated gel of the sugar only diet. The possible role of dietary bacteria in relation to functional aspects of olive fly physiology is discussed.     

Biocontrol of vascular streak dieback (Ceratobasidium theobromae) on cacao (Theobroma cacao) through induced systemic resistance and direct antagonism

Vascular streak dieback (VSD), caused by Ceratobasidium theobromae (P.H.B. Talbot &; Keane), has a considerable impact on cacao (Theobroma cacao L.) production in Southeast Asia. Two biocontrol experiments were set up to explore alternatives to ineffective chemical control of VSD. The effects on VSD development of (i) Trichoderma harzianum, superficially applied to leaves of mature cacao plants, and (ii) an inoculation with fungal (Trichoderma asperellum) and bacterial (Bacillus sp., Pseudomonas sp. and Enterobacter spp.) elicitors of systemic resistance in young cacao plants, were tested. After three months, cacao leaves treated with T. harzianum exhibited a significantly (p?p?Bacillus sp. and Enterobacter spp. After transplanting to the field (8 months after inoculation), both number of VSD-affected leaves per plant and number of VSD-affected leaves per branch per plant were significantly (p?T. asperellum did not show potential as an elicitor of systemic resistance in our experiment. More research is needed on the lasting effect of biocontrol treatments, as well as on their economic and ecological sustainability.     

Transgenic GNA Expressing Potato Plants Augment the Beneficial Biocontrol of Lacanobia Oleracea (Lepidoptera: Noctuidae) by the parasitoid Eulophus Pennicornis (Hymenoptera; Eulophidae)

The effect of expressing the gene encoding snowdrop lectin (Galanthus nivalis agglutinin, GNA) in transgenic potato plants, on parasitism of the phytophagous insect pest Lacanobia oleracea by the gregarious ectoparasitoid Eulophus pennicornis, was investigated in glasshouse trials. Expression of GNA (approx. 1.0% total soluble protein) by transgenic plants significantly reduced the level of pest damage, thus confirming previous studies. Furthermore, the presence of the parasitoid significantly reduced the levels of damage incurred either by the transgenic or control plants when compared to those plants grown in the absence of the parasitoid. For the GNA expressing plants the presence of the parasitoid resulted in further reductions (ca. 21%) in the level of damage caused by the pest species. The ability of the wasp to parasitise and subsequently develop on the pest larvae was not altered by the presence of GNA in the diet of the host. E. pennicornis progeny that developed on L. oleracea reared on GNA expressing plants showed no significant alteration in fecundity when compared with wasps that had developed on hosts fed on control potato plants, although mean size and longevity of female parasitoids was significantly reduced. The number of F ₂ progeny produced by parasitoids derived from hosts fed on GNA-expressing plants was not significantly different to those produced by parasitoids from hosts fed control plants. Results from the present study demonstrate that the use of transgenic plants expressing insecticidal proteins can be compatible with the deployment of beneficial insects and that the two factors may interact in a positive manner.     

Mycelia and spent fermentation broth of Beauveria bassiana incorporated into synthetic diets affect mortality,growth and development of larval Helicoverpa zea (Lepidoptera: Noctuidae)

Beauveria bassiana endophytically colonises corn (Zea mays) reducing tunneling from European corn borer (Ostrinia nubilalis). Endophytic colonisation of other plants by B. bassiana has been reported, and potentially, may reduce insect feeding on these plants. We evaluated the effects on larval growth and development, and mortality of different rates of dried, ground mycelia and water-soluble metabolites from fermentation broth culture of different isolates of B. bassiana incorporated into a synthetic diet and fed to neonate bollworm, Helicoverpa zea larvae. Development was delayed, weights of larvae were lower, and mortality was high for larvae fed the highest rates (1.0 and 5.0%, w/v) of mycelia incorporated diet compared to control. Insects fed diets containing mycelia of B. bassiana isolate 11-98 had the greatest mortality. Mortality was 100% for larvae fed 5% (w/v) mycelia incorporated diet of isolate 11-98, and 61% for isolate 3-00. For insects fed low rates (0.1 to 0.5%, w/v) of mycelia incorporated diet, mortality was lower, approximately 5% for isolate 11-98, and 5 to 14% for isolate 3-00. At the 0.1% (w/v) rate of mycelia incorporated diet, development occurred at an accelerated rate, compared to fungus-free controls, indicating increased nutrition in the lowest rate fungal diet. Mortality was low for all larvae fed diets containing spent fermentation broth of B. bassiana; however, development was delayed. Insects fed the highest rate (0.5%, v/v) of spent fermentation broth-amended diet had lower pupal weights, and a greater number of days to pupation than insects fed the lowest (0.1%, v/v) rate. Insects fed the 5% (v/v) rate of spent fermentation broth of isolates 11-98 and 3-00 had the longest days to pupation.     

Spider mites (Tetranychus urticae) perform poorly on and disperse from plants exposed to methyl jasmonate

Jasmonates are plant hormones involved in wound and defense responses against herbivorous arthropods. Methyl jasmonate (MeJA) is used experimentally to induce defense responses in plants. In experiments outlined here we utilized a novel preference assay with unwounded plants that allowed us to study the impact of a MeJA spray on subsequent Tetranychus urticae Koch (Acari: Tetranychidae) proliferation and preference. Spraying plants with 100 μm MeJA 1 day before infestation caused mites to disperse within 2 days from treated impatiens [Impatiens wallerana Hook f., ‘Super Elfin Pink’ (Balsaminaceae)], pansy [Viola × wittrockiana Gams, ‘Imperial Beaconsfield’ (Violaceae)], and tomato [Solanum lycopersicum L., ‘Big Boy’ (Solanaceae)] plants. In addition, MeJA application reduced mite proliferation rate on impatiens and pansy by 60% (measured 22–34 days after infestation). Proteinase inhibitor (PI) assays suggested that MeJA‐induced PIs alone were not responsible for the observed results in pansy and impatiens but may have been a factor in tomato. Implications of these results in the context of MeJA‐induced resistance responses and possible directions for future research and application are discussed.     

Contrary effects of jasmonate treatment of two closely related plant species on attraction of and oviposition by a specialist herbivore

Elevated jasmonic acid (JA) concentrations in response to herbivory can induce wounded plants to produce defences against herbivores. In laboratory and field experiments we compared the effects of exogenous JA treatment to two closely related cabbage species on the host‐searching and oviposition preference of the diamondback moth (DBM), Plutella xylostella. JA‐treated Chinese cabbage (Brassica campestris) was less attractive than untreated Chinese cabbage to ovipositing DBM, while JA‐treatment of common cabbage (B. oleracea) made plants more attractive than untreated controls for oviposition by this insect. Similar effects were observed when plants of the two species were damaged by DBM larvae. In the absence of insect‐feeding, or JA application, Chinese cabbage is much more attractive to DBM than common cabbage. Inducible resistance therefore appears to occur in a more susceptible plant and induced susceptibility appears to occur in a more resistant plant, suggesting a possible balance mechanism between constitutive and inducible defences to a specialist herbivore.     

Effects of Lactobacillus rhamnosus ATCC 7469 on Different Parameters Related to Health Status of Rainbow Trout (Oncorhynchus mykiss) and the Protection Against Yersinia ruckeri

In the current study, we investigated the effect of a probiotic bacterium (Lactobacillus rhamnosus ATCC 7469) microencapsulated with alginate and hi-maize starch and coated with chitosan on improving growth factors, body composition, blood chemistry, and the immune response of rainbow trout (initial weight: 18.41 ± 0.32 g). Four experimental diets were formulated to feed fish for 60 days. They were control diet without any additive (C), diet added with beads without probiotic (E), a probiotic sprayed to the diet (L.r), and encapsulated probiotic supplemented diet (E-L.r). The results indicated that feeding with E-Lr significantly improved weight gain (84.98 g) and feed conversion ratio (0.95) compared to the other groups (P < 0.05). Also, fish fed E-Lr diet had a significantly higher value of whole-body protein (17.51%), total protein in the blood (4.98 g/dL), lysozyme (30.66 U/mL), alternative complement pathway hemolytic activity (134 U/mL), superoxide dismutase (203 U/mg protein), and catalase (528.33 U/mg protein) (P < 0.05) as compared to those fed the control diet. Similarly, a higher relative expression of immune-related genes such as interleukin-1 (Il-1) and tumor necrosis factor-alpha (TNF-1α) were reported in those fed E-L.r and L.r diets respectively. Interestingly, the fish fed dietary E-L.r had a significantly lower value of lipid in the whole body (4.82%) and cholesterol in the blood (160.67%) in comparison with those fed the control diet (P < 0.05). At the end of the experiment, all groups were challenged by Yersinia ruckeri where the survival rate of rainbow trout fed dietary E-L.r (70.36%) was statistically higher than that of the others (P < 0.05). Overall, the results suggested that encapsulated probiotic Lact. rhamnosus ATCC 7469 acted better than unencapsulated probiotic and has a potential to improve growth performance, flesh quality, and the immune response of rainbow trout.

     

饲料类型对茶尺蠖幼虫肠道细菌多样性及幼虫存活率的影响

【目的】茶尺蠖是茶园中的重要害虫。研究茶尺蠖寄主食物-肠道菌群-茶尺蠖生长发育三者之间的关系对于茶尺蠖的防治具有重要的理论指导价值。【方法】分析不添加茶叶因子的纯人工饲料和茶树鲜叶对茶尺蠖幼虫的存活影响;用高通量测序技术分析不同饲料饲喂的茶尺蠖幼虫的肠道菌群异同。【结果】取食人工饲料的幼虫死亡率远远高于取食茶树鲜叶的幼虫;取食人工饲料的幼虫肠道细菌多样性和丰富度高于取食茶树鲜叶的幼虫;茶尺蠖幼虫肠道中存在很多促进宿主生长的细菌。【结论】饲料类型影响茶尺蠖幼虫的存活;饲料类型影响茶尺蠖幼虫肠道菌群结构。     

Similar attractiveness of maize volatiles induced by Helicoverpa armigera and Pseudaletia separata to the generalist parasitoid Campoletis chlorideae

Campoletis chlorideae Uchida (Hymenoptera: Ichneumonidae), a major larval endoparasitoid of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), also attacks many other noctuid caterpillars. We investigated the attractiveness of H. armigera‐ and Pseudaletia separata (Lepidoptera: Noctuidae)‐infested maize [Zea mays L. (Poaceae)] plants to C. chlorideae, and analyzed the volatiles emitted from infested plants and undamaged plants. Considering the reported specific induction of plant volatiles by elicitors in the caterpillar regurgitant, we also tested the response of the parasitoid to mechanically damaged plants treated with caterpillar regurgitant or water and measured the volatiles released by these plants. In wind‐tunnel bioassays, C. chlorideae was strongly attracted to herbivore‐induced maize volatiles. Mechanically damaged plants, whether they were treated with caterpillar regurgitant or water, were more attractive to the parasitoid than undamaged plants. The parasitoid did not distinguish between maize seedlings infested by the two noctuid insects, nor did they show a difference in attraction to mechanically damaged plants treated with caterpillar regurgitant or water. Coupled gas chromatography–mass spectrometer (GC‐MS) analysis revealed that 15 compounds were commonly emitted by herbivore‐infested and mechanically damaged maize plants, whereas only two compounds were released in minor amounts from undamaged plants. Infestation by H. armigera specifically induced four terpenoids, β‐pinene, β‐myrcene, D‐limonene, and (E)‐nerolidol, which were not induced by infestation of P. separata and mechanical damage, plus caterpillar regurgitant or water. Two compounds, geranyl acetate and β‐sesquiphellandrene, were also induced by the infestation of H. armigera, but not by the infestation of P. separata. All treated maize plants released volatiles in significantly larger total amounts than did undamaged plants. Maize plants infested by H. armigera emitted greater amounts of volatiles than plants infested by P. separata. The treatment with caterpillar regurgitant resulted in larger amounts of volatile emission than the treatment with water did in mechanically damaged plants. The amounts of emissions of individual compounds were also different between differently treated plants.     

Plant preference in relation to life history traits in the zoophytophagous predator Dicyphus hesperus

Dicyphus hesperus Knight (Heteroptera: Miridae) is an omnivorous predator used to control pests of greenhouse vegetables. Plant preferences and life history traits were studied using nine plant species: Lycopersicon esculentum Mill. (Solanaceae), Capsicum annuum L. (Solanaceae), Verbascum thapsus L. (Scrophulariaceae), Nepeta cataria L. (Lamiaceae), Stachys albotomentosa (Lamiaceae), Nicotiana tabacum L. (Solanaceae), Vicia sativa L. (Fabaceae), Zea mays L. (Gramineae), and Chrysanthemum coronarium L. (Asteraceae). Plants were selected from among potential target crops, natural hosts, plants used for mass rearing, and plants on which D. hesperus has not been reported. Plant preference was measured by multi‐choice host plant selection and oviposition assays. Development and reproduction were measured on each of the plant species on both a plant diet alone and on a plant diet supplemented with Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. Dicyphus hesperus females and nymphs expressed a preference for some plants over others. Plant preference ranged from low preference plants, such as Z. mays, V. sativa, C. coronarium, and C. annuum, to high preference plants such as V. thapsus, N. tabacum, and S. albotomentosa. When E. kuehniella eggs were supplied, there were few differences in the development time and fecundity of D. hesperus among plants, with the exception of corn and broad bean, where fecundity was lower. On a plant diet alone, nymphs were able to complete their development on V. thapsus, C. annuum, and N. cataria. However, mortality and development time were much lower on V. thapsus than on C. annuum and N. cataria. On most of the plant species D. hesperus did not lay any eggs when fed on a plant diet alone. On V. thapsus, females laid a few eggs and lived longer than when fed on prey. Dicyphus hesperus females tended to prefer host plants on which nymph survival without prey was greatest.     

Ontogenesis of intestine morphology and intestinal disaccharidases in chickens (Gallus gallus) fed contrasting purified diets

Two groups of growing posthatching Cornish x Rock cross chickens were fed with either a carbohydrate-containing (52.5%) or a carbohydrate-free diet. At 36 days after hatching some of the chicks in each group were shifted to the opposite diet. Chickens fed on a carbohydrate-containing diet grew faster and achieved higher asymptotic masses than chickens fed on a carbohydrate-free diet. Chickens fed on a carbohydrate-free diet had longer intestines and larger intestinal areas than chickens of the same mass fed on a carbohydrate-containing diet. In both groups sucrase and maltase activity (standardized by either intestinal area or mass) increased from day 1 to approximately day 17. After day 17, chickens fed on a carbohydrate-containing diet exhibited 1.8 and 1.9 times higher sucrase and maltase activities per unit intestinal area, respectively, than chickens fed on a carbohydrate-free diet. Analysis of covariance was used to estimate the contribution of sucrase and the sucrase-independent maltases to maltase activity, and to estimate the effect of diet on the sucrase-independent maltases. Sucrase contributed 80% and 75% of the maltase activity in carbohydrate and carbohydrate-free fed chickens, respectively. Chickens shifted from a carbohydrate-free to a carbohydrate diet converged in gross intestinal morphology and intestinal sucrase and maltase levels with carbohydrate-fed chickens within 8 days. Chickens shifted from carbohydrate to carbohydrate-free diets, in contrast, did not show appreciable changes in intestinal length and after 8 days had not reduced levels of sucrase and maltase to those of chickens fed on the carbohydrate-free diet. A comparison of integrated maltase intestinal activity with published data on glucose uptake showed that the ratio of maltose hydrolysis to glucose uptake seemed to be about 7 and to remain relatively invariant during ontogeny. Because so little is known about the interaction between hydrolysis and uptake in vivo, it is difficult to determine if this relatively high ratio represents excess hydrolytic capacity or if it is needed to provide high lumenal glucose concentrations that maximize uptake.Abbreviations m body mass - K _m Michaelis constant - K _m ^* apparent Michaelis constant - GI gastro-intestinal