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  • 1
    Electronic Resource
    Electronic Resource
    Effects of season-dependent irradiance levels and nitrogen-deficiency on photosynthesis and photoinhibition in field-grown rice (Oryza sativa) (2003)
    Oxford, UK : Munksgaard International Publishers
    Physiologia plantarum 117 (2003), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Photoinhibition and acclimation of photosynthesis in rice plants grown under N-sufficient (NS) and N-deficient (ND) field conditions were investigated during the tropical wet (WS) and dry (DS) seasons in the Philippines. Diurnal patterns of CO2 assimilation were examined. There was a transient peak in CO2 assimilation in the leaves of the NS plants in the early morning during the DS and the WS, which was not seen in the ND plants in either season. ND leaves had lower Ribulose bisphosphate carboxylase/oxygenase (Rubisco) contents and lower chlorophyll contents. A lowered quantum yield of photosystem II (φPSII) was observed in the ND plants at an intermediate irradiance though no differences between N treatments were seen at high irradiance. Analysis of carotenoids indicated a small increase in the de-epoxidation state of the xanthophyll cycle (DES) at mid-day in the ND leaves compared to NS. Photoinhibition was greater in ND leaves when incident mid-day irradiance was increased by altering the leaf angle. Although Rubisco contents were lower in ND plants, photosynthesis in situ did not decline proportionally. For NS plants, Chlorophyll content, but not Rubisco content, was season-dependent and results are discussed in terms of the interaction between irradiance use and N content of rice leaves.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1034/j.1399-3054.2003.00048.x
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  • 2
    Electronic Resource
    Electronic Resource
    Response of oxidative stress defense systems in rice (Oryza sativa) leaves with supplemental UV-B radiation (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Physiologia plantarum 101 (1997), S. 0 
    Details
    ISSN: 1399-3054
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The impact of elevated ultraviolet-B radiation (UV-B, 280–320 nm) on membrane systems and lipid peroxidation, and possible involvement of active oxygen radicals was investigated in leaves of two UV-B susceptible rice cultivars (Oryza sativa L. cvs IR74 and Dular). Rice seedlings were grown in a greenhouse for 10 days and then treated with biologically effective UV-B (UV-BBE) radiation for 28 days. Oxidative stress effects were evaluated by measuring superoxide anion (O2) generation rate, hydrogen peroxide (H2O2) content, malondialdehyde (MDA) concentration and relative electrolyte conductivity (EC) for IR74 and Dular at 0 (control), 6 or 13 kJ m−2 day−1 UV-BBE. Significant increases in these parameters were found in rice plants grown at 13 vs 0 kJ m−2 day−1 UV-BBE after 28 days; indicating that disruption of membrane systems may be an eventual reason for UV-B-induced injury in rice plants. There was a positive correlation between O2− generation and increases in EC or MDA in leaves. Activities of enzymatic and nonenzymatic free radical scavengers were measured for IR74 after 7, 14, 21 and 28 days of exposure to 13 or 0 UV-BBE to evaluate dynamics of these responses over time. Activities of catalase and superoxide dismutase (but not ascorbate peroxidase) and concentrations of ascorbic acid and glutathione were enhanced by 13 vs 0 UV-BBE after 14 days of UV-B exposure. Further exposure to 28 days of UV-B was associated with a decline in enzyme activities and ascorbic acid, but not glutathione. It is suggested that UV-B-induced injury may be associated with disturbance of active oxygen metabolism through the destruction and alteration of both enzymatic and nonenzymatic defense systems in rice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1399-3054.1997.tb01000.x
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  • 3
    Electronic Resource
    Electronic Resource
    Upper Thresholds of Nitrogen Uptake Rates and Associated Nitrogen Fertilizer Efficiencies in Irrigated Rice (1998)
    Springer
    Semigroup forum 90 (1998), S. 178-185 
    Details
    ISSN: 1432-2137
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Oryza sativa L.) have usually been conducted over a period of 7 to 14 d. Such a sampling interval may not accurately determine the maximum rate, since information concerning N uptake dynamics during the first week after N topdressing is limited. In this study, N uptake dynamics and fertilizer N recovery efficiency following N topdressing were determined with more frequent samplings. Field experiments were conducted at International Rice Research Institute (IRRI) and at the Philippine Rice Research Institute (PRRI) during the 1995 dry season. Treatments consisted of 0,50, and 100 kg N ha-1 applied at midtillering (MT) or panicle initiation (PI). Tissue N concentration and N uptake were measured 0, 2, 4, 6, 9, and 14 d after N application. Fertilizer N recovery efficiency was estimated using the difference method. At PI, maximum N uptake rates of 9 to 12 kg ha-1d-1 were measured over the 4-d period following application of 100 kg N ha-1, which is up to double the previously reported maximum value of 6 kg ha-1d-1. The much larger estimates of maximum N uptake rates in our study probably resulted from more frequent sampling than in previous studies. Nitrogen uptake rates at PI were similar, regardless of N rate at MT. Recovery efficiency of N applied at PI reached 74 to 78%, and was significantly higher than that at MT. Recovery efficiency was relatively insensitive to the amount of N applied at MT and PI, which suggests that high N fertilizer efficiency can be achieved with large rates of applied N when growth conditions are favorable.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/
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  • 4
    Electronic Resource
    Electronic Resource
    Grain filling pattern and cytokinin content in the grains and roots of rice plants (2000)
    Springer
    Plant growth regulation 30 (2000), S. 261-270 
    Details
    ISSN: 1573-5087
    Keywords: cytokinins ; gibberellins (GA) ; grain filling pattern ; grain filling percentage ; indole-3-acetic acid (IAA) ; rice (Oryza sativa L.) ; zeatin ; zeatin riboside
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Grain filling patterns and their relationships withzeatin (Z), zeatin riboside (ZR), indole-3-acetic acid(IAA) and gibberellin (GA) contents in the grains androots during grain development were examined in sixrice (Oryza sativa L.) genotypes grown in thefield and in water culture. Three grain fillingpatterns based on the filling rate of superior andinferior spikelets were observed, i.e., fastsynchronous: all spikelets started filling early andfast at the early filling stage; slowsynchronous: all spikelets filled slowly at the earlyfilling stage and reached the maximum filling ratelate; and asynchronous: superior spikeletsstarted filling and reached the maximum filling ratemuch earlier than the inferior ones. The order ofgrain filling percentage in the three types of grainfilling patterns was: fast synchronous 〉asynchronous 〉 slow synchronous. Changes in Z + ZRcontents in the superior and inferior spikelets wereassociated with the grain filling patterns. Grainfilling percentage was significantly correlated withZ + ZR contents in the grains and roots at the earlyand middle grain filling stages. IAA and GA(GA1 + GA3 + GA4)contents in the grains and roots were notsignificantly correlated with grain fillingpercentage. The results suggest that cytokinins in thegrains and roots during the early phase of graindevelopment play an important role in regulating grainfilling pattern and consequently influence grainfilling percentage.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006356125418
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  • 5
    Electronic Resource
    Electronic Resource
    Influence of supplemental ultraviolet-B on indoleacetic acid and calmodulin in the leaves of rice (Oryza sativa L.) (1997)
    Springer
    Plant growth regulation 21 (1997), S. 59-64 
    Details
    ISSN: 1573-5087
    Keywords: growth habit ; ipt gene ; phytohormones ; potato plants in vitro ; Solanum tuberosum L. ; tuberization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract IR68 and Dular rice cultivars were grown under ambient, 13.0 (simulating 20% ozone depletion) and 19.1 (simulating 40% ozone depletion) kJ m-2 day-1 of biologically effective ultraviolet-B (UV-BBE) for 4 weeks. Plant height and leaf area were significantly reduced by supplemental UV-BBE radiation. Greater reduction in leaf area than of plant height was observed. A decrease in indole-3-acetic acid (IAA) content and increase in peroxidase and IAA oxidase activities of UV-B treated plants in both cultivars were observed compared with ambient control. Calmodulin content also decreased after plants were treated with high supplemental UV-B for two weeks and medium UV-B treatment for four weeks. The results indicated that peroxidase and IAA oxidase activities in rice leaves were stimulated by supplemental UV-B, resulting in the destruction of IAA which in turn may cause inhibition of rice leaf growth. Although the mechanism is unclear, calmodulin is most likely involved in leaf growth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005777125940
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  • 6
    Electronic Resource
    Electronic Resource
    Leaf photosynthetic rate is correlated with biomass and grain production in grain sorghum lines (1991)
    Springer
    Photosynthesis research 28 (1991), S. 1-7 
    Details
    ISSN: 1573-5079
    Keywords: carbon exchange rate ; genetic variation ; grain yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Significant genetic variation in leaf photosynthetic rate has been reported in grain sorghum [Sorghum biocolor (L.) Moench]. The relationships between leaf photosynthetic rates and total biomass production and grain yield remain to be established and formed the purpose of this experiment. Twenty two grain sorghum parent lines were tested in the field during the 1988 growing season under well-watered and water-limited conditions. Net carbon assimilation rates were measured at mid-day during the 30 day period from panicle initiation to head exertion on upper-most fully expanded leaves using a portable photosynthesis system (LI-6200). Total biomass and grain production were determined at physiological maturity. The lines exhibited significant genetic variation in leaf photosynthetic rate, total biomass production and grain yield. Significant positive correlations existed between leaf photosynthesis and total biomass and grain production under both well-watered and water-limited conditions. The results suggest that leaf photosynthetic rate measured prior to flowering is a good indicator of productivity in grain sorghum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00027171
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