Seed coat cell turgor in chickpea is independent of changes in plant and pod water potential.
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Turgor pressure in cells of the pod wall and the seed coat of chickpea (Cicer arietinum L.) were measured directly with a pressure probe on intact plants under initially dry soil conditions, and after the plants were irrigated. The turgor pressure in cells of the pod wall was initially 0.25 MPa, and began to increase within a few minutes of irrigation. By 2-4 h after irrigation, pod wall cell turgor had increased to 0.97 MPa. This increase in turgor was matched closely by increases in the total water potential of both the pod and the stem, as measured by a pressure chamber. However, turgor pressure in cells of the seed coat was relatively low (0.10 MPa) and was essentially unchanged up to 24 h after irrigation (0.13 MPa). These data demonstrate that water exchange is relatively efficient throughout most of the plant body, but not between the pod and the seed. Since both the pod and the seed coat are vascularized tissues of maternal origin, this indicates that at least for chickpea, isolation of the water relations of the embryo from the maternal plant does not depend on the absence of vascular or symplastic connections between the embryo and the maternal plant. (+info)
Urea is a product of ureidoglycolate degradation in chickpea. Purification and characterization of the ureidoglycolate urea-lyase.
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A ureidoglycolate-degrading activity was analyzed in different organs of chickpea (Cicer arietinum). Activity was detected in all the tissues analyzed, but highest levels of specific activity were found in pods, from which it has been purified and characterized. This is the first ureidoglycolate-degrading activity that has been purified to homogeneity from any photosynthetic organism. Only one ureidoglycolate-degrading activity was found during the purification. The enzyme was purified 1,500-fold, and specific activity for the pure enzyme was 8.6 units mg(-1), which corresponds with a turnover number of 1,600 min(-1). The native enzyme has a molecular mass of 180 kD and consists of six identical or similar-sized subunits of 31 kD each. The enzyme exhibited hyperbolic, Michaelian kinetics for (-) ureidoglycolate with K(m) values of 6 and 10 microM in the presence or absence of Mn(2+), respectively. Optimum pH was between 7 and 8 and maximum activity was found at temperatures above 70 degrees C, the enzyme being extremely stable and resistant to heat denaturation. The activity was inhibited by EDTA and enhanced by several bivalent cations, thus suggesting that the enzyme is a metalloprotein. This enzyme has been characterized as a ureidoglycolate urea-lyase (EC 4.3.2.3), which catalyzes the degradation of (-) ureidoglycolate to glyoxylate and urea. This is the first time that such an activity is detected in plant tissues. A possible function for this activity and its implications in the context of nitrogen mobilization in legume plants is also discussed. (+info)
Copper amine oxidase expression in defense responses to wounding and Ascochyta rabiei invasion.
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Wounding chickpea (Cicer arietinum) internodes or cotyledons resulted in an increase in the steady-state level of copper amine oxidase (CuAO) expression both locally and systemically. Dissection of the molecular mechanisms controlling CuAO expression indicated that jasmonic acid worked as a potent inducer of the basal and wound-inducible CuAO expression, whereas salicylic acid and abscisic acid caused a strong reduction of the wound-induced CuAO expression, without having any effect on the basal levels. Epicotyl treatment with the CuAO mechanism-based inhibitor 2-bromoethylamine decreased hydrogen peroxide (H(2)O(2)) levels in all the internodes, as evidenced in vivo by 3,3'-diaminobenzidine oxidation. Moreover, inhibitor pretreatment of wounded epicotyls resulted in a lower accumulation of H(2)O(2) both at the wound site and in distal organs. In vivo CuAO inhibition by 2-bromoethylamine after inoculation of resistant chickpea cv Sultano with Ascochyta rabiei resulted in the development of extended necrotic lesions, with extensive cell damage occurring in sclerenchyma and cortical parenchyma tissues. These results, besides stressing the fine-tuning by key signaling molecules in wound-induced CuAO regulation, demonstrate that local and systemic CuAO induction is essential for H(2)O(2) production in response to wounding and indicate the relevance of these enzymes in protection against pathogens. (+info)
The effects of salinity and sodicity upon nodulation and nitrogen fixation in chickpea (Cicer arietinum).
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Production of grain legumes is severely reduced in salt-affected soils because their ability to form and maintain nitrogen-fixing nodules is impaired by both salinity and sodicity (alkalinity). Genotypes of chickpea, Cicer arietinum, with high nodulation capacity under stress were identified by field screening in a sodic soil in India and subsequently evaluated quantitatively for nitrogen fixation in a glasshouse study in a saline but neutral soil in the UK. In the field, pH 8.9 was the critical upper limit for most genotypes studied but genotypes with high nodulation outperformed all others at pH 9.0-9.2. The threshold limit of soil salinity for shoot growth was at ECe 3 dS m(-1), except for the high-nodulation selection for which it was ECe 6. Nodulation was reduced in all genotypes at salinities above 3 dS m(-1) but to a lesser extent in the high-nodulation selection, which proved inherently superior under both non-saline and stress conditions. Nitrogen fixation was also much more tolerant of salinity in this selection than in the other genotypes studied. The results show that chickpea genotypes tolerant of salt-affected soil have better nodulation and support higher rates of symbiotic nitrogen fixation than sensitive genotypes. (+info)
Role of salicylic acid in systemic resistance induced by Pseudomonas fluorescens against Fusarium oxysporum f. sp. ciceri in chickpea.
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Selected isolates of Pseudomonas fluorescens (Pf1-94, Pf4-92, Pf12-94, Pf151-94 and Pf179-94) and chemical resistance inducers (salicylic acid, acetylsalicylic acid, DL-norvaline, indole-3-carbinol and lichenan) were examined for growth promotion and induced systemic resistance against Fusarium wilt of chickpea. A marked increase in shoot and root length was observed in P. fluorescens treated plants. The isolates of P. fluorescens systemically induced resistance against Fusarium wilt of chickpea caused by Fusarium. oxysporum f.sp. ciceri (FocRs1), and significantly (P = 0.05) reduced the wilt disease by 26-50% as compared to control. Varied degree of protection against Fusarium wilt was recorded with chemical inducers. The reduction in disease was more pronounced when chemical inducers were applied with P. fluorescens. Among chemical inducers, SA showed the highest protection of chickpea seedlings against wilting. Fifty two- to 64% reduction of wilting was observed in soil treated with isolate Pf4-92 along with chemical inducers. A significant (P = 0.05; r = -0.946) negative correlation was observed in concentration of salicylic acid and mycelial growth of FocRs1 and at a concentration of 2000 microg ml(-1) mycelial growth was completely arrested. Exogenously supplied SA also stimulated systemic resistance against wilt and reduced the disease severity by 23% and 43% in the plants treated with 40 and 80 microg ml(-1) of SA through root application. All the isolates of P. fluorescens produced SA in synthetic medium and in root tissues. HPLC analysis indicated that Pf4-92 produced comparatively more SA than the other isolates. 1700 to 2000 nanog SA g(-1) fresh root was detected from the application site of root after one day of bacterization whereas, the amount of SA at distant site ranged between 400-500 nanog. After three days of bacterization the SA level decreased and was found more or less equal at both the detection sites. (+info)
Effects of long-term consumption and single meals of chickpeas on plasma glucose, insulin, and triacylglycerol concentrations.
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BACKGROUND: Legumes are recommended for better glucose control in persons with diabetes. Whether subjects with normal insulin sensitivity would also benefit from legume consumption is not clear. OBJECTIVE: Our goal was to compare the effects on insulin sensitivity of chickpea-based and wheat-based foods when eaten as single meals or over 6 wk. DESIGN: Acute and long-term studies were conducted in healthy middle-aged men and women. In the acute study (n = 19), plasma glucose, insulin, and calculated homeostasis model assessment (HOMA; an index of insulin sensitivity) were measured on 3 separated days over 3 h after the subjects consumed 50-g available carbohydrate loads from either chickpeas, wheat-based foods, or white bread. The long-term comparison (n = 20) was a randomized, crossover study in which chickpea-based and wheat-based foods were eaten for 6 wk each. Plasma glucose, insulin, and HOMA were measured in the fasting state and 2 h after a 75-g glucose load. RESULTS: After single meals, plasma glucose was substantially lower 30 and 60 min after the chickpea meal than after the other 2 meals (P < 0.05), and plasma insulin and HOMA were lower at 120 min (P < 0.05 for both). Despite this, the long-term study failed to show significant differences in plasma glucose, insulin, or HOMA either in the fasting state or after a glucose load. CONCLUSION: Compared with a wheat-based meal, a single chickpea-based meal led to a lesser response in plasma glucose and insulin concentrations, but this was not translated into long-term improvement in insulin sensitivity over 6 wk, at least in healthy subjects. (+info)
Internal recycling of respiratory CO2 in pods of chickpea (Cicer arietinum L.): the role of pod wall, seed coat, and embryo.
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It has previously been proposed that respiratory CO2 released from the embryo in grain legume pods is refixed by a layer of cells on the inner pod wall. In chickpea this refixation process is thought to be of significance to the seed carbon budget, particularly under drought. In this study it is reported that the excised embryo, seed coat, and pod wall in chickpea are all photosynthetically competent, but the pod wall alone is capable of net O2 evolution over and above respiration. The predominant role of the pod wall in refixation is supported by measurements of fixation of isotopically labelled CO2, which show that more than 80% of CO2 is fixed by this tissue when provided to the pod interior. Chlorophyll concentrations are of the same order for embryo, seed coat, and pod wall tissues in younger pods on both an area and a fresh weight basis, but decline differentially with development from 12-30 d after podding. Imaging of chlorophyll distribution in the pod wall suggests that less than 15% of chloroplasts are located in the inner layer of cells thought to refix CO2 in legumes; this would be sufficient to refix less than 40% of respired CO2. It is concluded that while all tissues of the pod are capable of refixing respiratory carbon, the entire pod wall is responsible for the majority of this process, rather than a specialized layer of cells on the inner epidermis. The role of this fixed carbon in the pod for reallocation to the seed is discussed (+info)
Sulphur and nitrogen nutrition influence the response of chickpea seeds to an added, transgenic sink for organic sulphur.
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In order to increase the concentration of the nutritionally essential sulphur amino acids in seed protein, a transgene encoding a methionine- and cysteine-rich protein, sunflower seed albumin (SSA), was transferred to chickpeas (Cicer arietinum L). Transgenic seeds that accumulated SSA contained more methionine and less oxidized sulphur than the controls, suggesting that additional demand for sulphur amino acids from the expression of the transgene stimulated sulphur assimilation. In addition, the activity of trypsin inhibitors, a known family of endogenous, sulphur-rich chickpea seed proteins, was diminished in transgenic, SSA-containing seeds compared with the non-transgenic controls. Together, these results indicate that the reduced sulphur sequestered into SSA was supplied partly by additional sulphur assimilation in the developing transgenic seeds, and partly by some diversion of sulphur amino acids from endogenous seed proteins. Growth of chickpeas on nutrient with a high sulphur-to-nitrogen ratio increased the total seed sulphur content and the accumulation of sulphur amino acids in the seeds, and partly mitigated the effect of SSA accumulation on the trypsin inhibitor amount. The results suggest that free methionine and O-acetylserine (OAS) acted as signals that modulated chickpea seed protein composition in response to the variation in sulphur demand, as well as in response to variation in the nitrogen and sulphur status of the plant. (+info)