Characteristic early membrane effects induced by tryptophan in pulvinar motor cells.

Tryptophan at concentrations higher than 0.1 mM, triggered characteristic early physiological effects such as rapid (within 5 min) dose-dependent membrane hyperpolarization in Mimosa pudica motor cells and modification of the time course of the spontaneous proton efflux monitored in the incubation medium of pulvinar tissues. The rapid modifications of the leaf turgor-mediated movements seen on the primary pulvini of M. pudica following a shock and on Cassia fasciculata leaflets during a transition from light to darkness indicate that tryptophan disturbed the ionic migrations involved in the electrophysiological events and in the osmocontractile reaction of the motor cells. These reactions were specific to tryptophan compared to those induced by serine and 5-hydroxytryptophan. The tryptophan mode of action cannot be linked to a direct modification of the plasma membrane H+-ATPase activity as monitored on purified pulvinar plasma membrane vesicles. The tryptophan metabolism-linked products tryptamine and indole also inhibited the motile reactions, activated in a continuous manner the H+ secretion of pulvinar tissues and showed properties of a protonophore and an ATPase activity inhibitor on plasma membrane vesicles, respectively. The specific behavior of tryptophan in the reaction studies here is discussed in light of the previously reported action of phytohormones.

Cysteine: A multifaceted amino acid involved in signaling, plant resistance and antifungal development.

Early effects induced by cysteine were monitored using the model of Mimosa pudica pulvinar cells. Rapid dose-dependent membrane depolarization (within seconds) and modification of proton secretion (within minutes) were triggered at cysteine concentrations higher than 0.1 mM. These effects did not result from a modification of the plasma membrane H+-ATPase activity nor from a protonophore effect as shown by assays on plasma membrane vesicles isolated from pulvinar tissues. In a 0.5-10 mM range, cysteine inhibited the ion-driven turgor-mediated seismonastic reaction of Mimosa pudica primary pulvini and the dark-induced movement of Cassia fasciculata leaflets. At concentrations higher than 1 mM, it induced a long-lasting leaflet necrosis dependent on the concentration and treatment duration. Electron microscopy showed that cysteine induced important damage in the nucleus, mitochondria, endoplasmic reticulum and Golgi of the M. pudica motor cell. Cysteine inhibited in a concentration-dependent manner, from 0.5 to 20 mM, both the mycelial growth and the spore germination of the fungal pathogens Phaeomoniella chlamydospora and Phaeoacremonium minimum implicated in esca disease of grapevines. Using [35S] cysteine, we showed that the amino acid was absorbed following leaf spraying, translocated from leaves to other parts of grapevine cuttings and accumulated within trunks and roots. Therefore, cysteine showed relevant properties to be a candidate able to control fungal diseases either by acting as an early signal directing plant host reaction or/and by acting directly on fungal development.

Effect of natural gas flaring upon the butterfly, Eurema hecabe (Lepidoptera: Pieridae) and its host plant, Cassia tora (Fabales: Fabaceae) in two group gathering stations of Assam, India: an approach of environmental monitoring.

Apart from other pollutants, flaring of natural gas adds carbon dioxide into the environment and changes the atmospheric composition, including temperature and humidity. As a major gaseous product, carbon dioxide changes plant structural components as well as herbivores, i.e., insect by dilution of nitrogen under such circumstances. Present analysis demonstrated the impact of gas flaring upon adjoining biota especially Eurema hecabe butterfly and its host plant, Cassia tora in some wells (group gathering stations) of Assam, India. Analysis, pertaining from the current investigation, documented higher carbon dioxide as well as temperature in the studied flaring sites. Apart from this, reduction of leaf nitrogen, SLA, and chlorophyll with increasing in LDMC, thickness, and carbon in the studied plant as well as poor developmental rate, RGR, ECD with high RCR in insect indicated severe impact of flaring in those areas. Simulation studies with different concentration of CO2 in open top chamber on the plant and butterfly also revealed similar trend of results.

[Effects of drought stress on growth and water use efficiency of two medicinal plants].

Growth characteristics, stable carbon isotope discrimination (Delta13C), water use efficiency (WUE), and their correlation of Cassia obtusifolia and Isatis indigotica were measured at three soil water levels, i. e., 30%, 50% and 75% of field water holding capacity (FWHC), and at three growth stages. The growth indices of the two medicinal plants at 75% of FWHC were higher than those at 30% and 50% of FWHC, suggesting that the two medicinal plants could obtain high production under sufficient moisture condition. The Delta13C(A) (aboveground biomass-based Delta13C) and Delta13C(T) (total biomass-based Delta13C) decreased, and the WUE(A) (aboveground biomass-based WUE) and WUE(T) (total biomass-based WUE) of C. obtusifolia and I. indigotica increased with the increasing degree of drought stress. The growth indices of the two medicinal plants had little difference in the different water treatments, which indicated that the two medicinal plants were insensitive to drought stress. Water use efficiency of I. indigotica had significant negative relationships with aboveground biomass and total biomass, while that of C. obtusifolia had a significant positive correlation with the root/shoot ratio.

Response of three semi-arid plant species to fluoride; consequences for chlorophyll florescence.

The study was done to investigate the ability of three semi-arid plant species viz. Acacia tortilis, Cassia fistula and Prosopis juliflora to adapt to fluoride (F) stress. Here we examined the changes in activities of chlorophyll a fluorescence and photosynthetic pigment concentration during early growth of these plants. One month old plants were treated with 10, 20, and 50 mg kg(-1) F in soilrite. We did not observe any major change in photosynthetic performance of these plants during early growth. This was revealed by ETR, ETRmax, PPFD-sat and deltaF/Fm'-sat values which were higher in these plants. The decrease in chl a, chl b and total chl concentrations were significant only at 5 days. For most of the parameters, C. fistula was found to be more sensitive to F stress and P. juliflora showed least damage from F. The lesser inhibition in the parameters reflected the F tolerant nature of these plants with respect to photosynthesis. This opens the possibility of potential use of these species for treatment of F contaminated soil and water.

Drought induced changes in growth, leaf gas exchange and biomass production in Albizia lebbeck and Cassia siamea seedlings.

Diurnal trends in net photosynthesis rate (P(N)), stomatal conductance (g(s)), water use efficiency (WUE) and biomass were compared in six-month-old seedlings of Albizia lebbeck and Cassia siamea, under different levels of drought stress. The potted plants were subjected to four varying drought treatment by withholding watering for 7 (D1), 14(D2) and 25 (D3) days. The fourth group (C) was watered daily and treated as unstressed (control). Species differed significantly (p < 0.001) in their physiological performance under varying stress conditions. Higher P(N) of 11.6 +/- 0.05 in control followed by 4.35 +/- 0.4 in D1 and 2.83 +/- 0.18 micromol m(-2) s(-1) in D2 was observed in A. lebbeck. A significant (p < 0.001) reduction in P(N) was observed in C. siamea (C 7.65 +/- 0.5 micromol m(-2) s(-1), D1, 2.56 +/- 0.33 micromol m(-2) s(-1) and D2, 1.4 +/- 0.01 micromol m(-2) s(-1)) at 9 hr. A positive correlation was seen between P(N) and g(s) (A. lebbeck, r2 = 0.84; C. siamea, r2 = 0.82). Higher WUE was observed in C. siamea (D2, 7.1 +/- 0.18 micromol m(-2) s(-1); D3, 8.39 +/- 0.11 micromol m(-2) s(-1)) than A. lebbeck, (control, 7.58 +/- 0.3 micromol m(-2) s(-1) and D3, 8.12 +/- 0.15 micromol m(-2) s(-1)). The chlorophyll and relative water content (RWC) was more in A. lebbeck than C. siamea. Maximum biomass was produced by A. lebbeckthan C. siamea. From the study, one could conclude that A. lebbeckis better than C. siamea in adopting suitable resource management strategy and be best suited for the plantation programs in the semi-arid dry lands.

Control of Alternaria alternata by cassia oil in combination with potassium chloride or sodium chloride.

AIMS: To compare antifungal effects of cassia oil alone and in combination with potassium chloride (KCl) or sodium chloride (NaCl) against Alternaria alternata in vitro and in vivo. METHODS AND RESULTS: The inhibitory effect of cassia oil alone, or in combination with KCl and NaCl were tested in vitro. The spore germination and germ tube elongation of the pathogen was evaluated in potato dextrose broth with light microscopy analysis. The inhibitory effect of cassia oil alone, or in combination with KCl and NaCl, was determined on cherry tomatoes in vivo. The cassia oil in combination with KCl and NaCl exhibited strong antifungal effect in vivo and in vitro. CONCLUSIONS: The antifungal effect of cassia oil against Alt. alternata was enhanced significantly by combining with KCl and NaCl both in vitro and in vivo. SIGNIFICANCE AND IMPACT OF THE STUDY: The combination of cassia oil and KCl or NaCl may enhance antifungal effect of cassia oil and reduce cost.

Phytotoxicity of Phytolacca americana leaf extracts on the growth, and physiological response of Cassia mimosoides.

We examined the allelochemical effects of control soil, native soil (treated soil), and leaf extracts of Phytolacca americana (pokeweed) on the germination rate and seedling growth of Cassia mimosoides var. nomame. We also studied the resulting changes in root-tip ultrastructure and peroxidase isozyme biochemistry. P. americana leaf extract inhibited seed germination, seedling growth, and biomass when compared to control and treated soil. Root and shoot growth in treated soil was stimulated relative to control soil, but root growth was inhibited by 50% in the leaf extract treatment. Biomass of C. mimosoides seedlings grown on leaf extract was reduced sevenfold when compared to the control seedlings. The amounts of total phenolic compounds in the leaf extract, treated soil, and control soil were 0.77, 0.14, and 0.03 mg l(-1), respectively. The root tips of C. mimsoides treated with leaf extracts of P. americana showed amyloplasts and large central vacuoles with electron-dense deposits inside them when compared to control root tips. The activity of guaiacol peroxidase (GuPOX) in whole plant, roots, and shoots of C. mimosoides increased as leaf extract increased; maximum activity was observed in extract concentrations of 75% and higher. Root GuPOX activity was three times higher than in shoots. Therefore, we conclude that inhibition of C. mimosoides growth is related to the phenolic compounds in the P. americana leaf extract and the ultrastructure changes in root-tip cells and increased GuPOX activity is a response to these allelochemicals.

Nitric oxide reduces aluminum toxicity by preventing oxidative stress in the roots of Cassia tora L.

Nitric oxide (NO) as a key signaling molecule has been involved in mediation of various biotic and abiotic stress-induced physiological responses in plants. In the present study, we investigated the effect of NO on Cassia tora L. plants exposed to aluminum (Al). Plants pre-treated for 12 h with 0.4 mM sodium nitroprusside (SNP), an NO donor, and subsequently exposed to 10 microM Al treatment for 24 h exhibited significantly greater root elongation as compared with the plants without SNP treatment. The NO-promoted root elongation was correlated with a decrease in Al accumulation in root apexes. Furthermore, oxidative stress associated with Al treatment increased lipid peroxidation and reactive oxygen species, and the activation of lipoxygenase and antioxidant enzymes was reduced by NO. Such effects were confirmed by the histochemical staining for the detection of peroxidation of lipids and loss of membrane integrity in roots. The ameliorating effect of NO was specific, because the NO scavenger cPTIO [2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethylinidazoline-1-oxyl-3-oxide] completely reversed the effect of NO on root growth in the presence of Al. These results indicate that NO plays an important role in protecting the plant against Al-induced oxidative stress.

Floral biology and reproductive system of enantiostylous Senna corymbosa (Caesalpiniaceae)

The genus Senna (K.Bahuin) Miller (Cassieae) is represented in Argentina by 35 species and several varieties distributed in temperate, tropical and subtropical regions, and presents a high degree of endemism. Some taxa are used for medicine, animal foraging and ornamental purposes. Floral morphology, phases, rewards, attractants, visitors, pollen, reproductive system, P/O ratio, OCI and ISI indexes of enantiostylous Senna corymbosa were analyzed for morphological androecial differentiation and possible related functional differences between stamens groups. The study was carried out over three consecutive flowering seasons in March of 1999, 2000 and 2001, in two populations near the city of Buenos Aires, Argentina. The species has a buzz-pollination syndrome. The pollinators are Bombus atratus that vibrate the stamens, leading to nothotribic or sternotribic deposition of pollen. P/O ratio and pollen production were high thanks to the precise pollinating mechanism that needs a large delivery of pollen to ensure effective pollen deposition. P/O ratio also indicates that the species is xenogamous, although geitonogamy and autogamy (only induced, not spontaneous)were also recorded. The species is self-compatible. There were differences in hand-pollination treatments between long and medium stamens in fruit set, as well as in vitro differential fertility between their pollen grains. Hence, there are morphological and functional androecium differences: the medium stamens play a nutritional role while the long ones play a reproductive one. These differences are reflected in the breeding system. Moreover, differential fertility and enantiostyly may diminish the effects of self-compatibility by partially reducing the contribution of geitonogamy to selfing

Se analizaron la morfología y fases florales, recompensa, atractivos, visitantes, polen, sistema reproductivo, índices OCI e ISI y relación polen/óvulo de la especie enantiostílica Senna corymbosa. El objetivo fue estudiar su biología floral y determinar la posible presencia de diferenciación morfológica en el androceo. Era importante saber si las diferencias morfológicas reflejaban diferencias funcionales entre los grupos de estambres. El estudio se llevó a cabo durante tres estaciones de floración consecutivas en marzo de 1999,2000 y 2001,sobre dos poblaciones presentes en zonas protegidas de la ciudad de Buenos Aires, Argentina. La especie presenta un síndrome de polinización vibrátil (buzz-pollination).Los polinizadores son individuos de Bombus atratus, capaces de vibrar los estambres y extraer polen, el que se deposita nototríbica y/o esternotríbicamente. La relación P/O fue extremadamente elevada, así como la producción de polen. Esto se relaciona con el comportamiento de los visitantes y con la alta precisión del mecanismo de polinización, que requiere una gran cantidad de polen para asegurar su efectiva deposición en el cuerpo del insecto. La relación P/O indica que la especie es xenógama, aunque se registraron también geitonogamia y autogamia inducidas. La especie, por lo tanto, es autocompatible. Se encontraron diferencias en los tratamientos de polinización manual entre estambres largos y medianos en cuanto al establecimiento de frutos, así como una fertilidad diferencial in vitro entre sus tipos polínicos. Existen, así, diferencias morfológicas y funcionales en el androceo: los estambres medianos tienen un papel nutricional mientras que los largos cumplen un papel reproductivo. Estas diferencias se reflejan en el sistema de cruzamiento. Más aún, la fertilidad diferencial y la enantiostilia disminuyen los efectos de la autocompatibilidad reduciendo parcialmente la contribución de la geitonogamia a la endogamia

Floral biology and reproductive system of enantiostylous Senna corymbosa (Caesalpiniaceae).

The genus Senna (K. Bahuin) Miller (Cassieae) is represented in Argentina by 35 species and several varieties distributed in temperate, tropical and subtropical regions, and presents a high degree of endemism. Some taxa are used for medicine, animal foraging and ornamental purposes. Floral morphology, phases, rewards, attractants, visitors, pollen, reproductive system, P/O ratio. OCI and ISI indexes of enantiostylous Senna corymbosa were analyzed for morphological androecial differentiation and possible related functional differences between stamens groups. The study was carried out over three consecutive flowering seasons in March of 1999, 2000 and 2001, in two populations near the city of Buenos Aires, Argentina. The species has a buzz-pollination syndrome. The pollinators are Bombus atratus that vibrate the stamens, leading to nothotribic or stemotribic deposition of pollen. P/O ratio and pollen production were high thanks to the precise pollinating mechanism that needs a large delivery of pollen to ensure effective pollen deposition. P/O ratio also indicates that the species is xenogamous, although geitonogamy and autogamy (only induced, not spontaneous) were also recorded. The species is self-compatible. There were differences in hand-pollination treatments between long and medium stamens in fruit set, as well as in vitro differential fertility between their pollen grains. Hence, there are morphological and functional androecium differences: the medium stamens play a nutritional role while the long ones play a reproductive one. These differences are reflected in the breeding system. Moreover, differential fertility and enantiostyly may diminish the effects of self-compatibility by partially reducing the contribution of geitonogamy to selfing.

Population differentiation in an annual legume: local adaptation.

Studies of many plants species have demonstrated adaptive genetic differentiation to local environmental conditions. Typically these studies are conducted to evaluate adaptation to contrasting environments. As a consequence, although local adaptation has been frequently demonstrated, we have little information as to the spatial scale of adaptive evolution. We evaluated adaptive differentiation between populations of the annual legume Chamaecrista fasciculata using a replicated common-garden design. Study sites were established in three field locations that are home to native populations of C. fasciculata. Each location was planted for two years with seed from the population native to the study site (home population) and populations located six distances (0.1-2000 km) from each site (transplanted populations). Seeds were planted into the study sites with minimum disturbance to determine the scale of local adaptation, as measured by a home-site fitness advantage, for five fitness components: germination, survival, vegetative biomass, fruit production, and the number of fruit produced per seed planted (an estimate of cumulative fitness). For all characters there was little evidence for local adaptation, except at the furthest spatial scales. Patterns of adaptive differentiation were fairly consistent in two of the three sites, but varied between years. Little genetic variation was expressed at the third site. These results, combined with previous estimates of limited gene flow, suggest that metapopulation processes and temporal environmental variation act together to reduce local adaptation, except over long distances.

Nodulation studies in species of genus Cassia.

An examination of eight species of Cassia for nodulation under natural unsterilized soils of different types from varied agroclimatic regions, as well as under aseptic conditions, inoculated with rhizobia, representing all the 8 cross inoculation groups, showed lack of nodulation in all the tested species. The absence of specific strains of rhizobia and the morpho-physiological features of the non-nodulating species of Cassia were considered the possible non-nodulating causes.