Rate Of Dry Matter Production Research Articles

Determination of the Optimal and Lethal Dose for Mutagenicity of Rice Cultivars by Ethel Methane Sulphate

The experiment was carried out in the laboratories of the Department of Field Crops - College of Agriculture - Al-Qasim Green University to study optimal and lethal doses for mutagenicity of rice (Oryza sativa L.) cultivars by Ethel Methane Sulphate. The experiment design included two factors, the first factor being three cultivars : (V1= Amber 33, V2= Jasmine, and V3= Tigris) and the second factor nine concentrations (E0 = 0, E1 = 0.5, E2 = 1, E3=1.5, E4 = 2, E5 = 2.5, E6 =3, E7 =3.5 and E4 =4, respectively). The treatments were distributed in a factorial experiment according to the design of a complete randomized design (CRD) with three replications. The results obtained showed that the control treatment recorded the highest germination percentage but did not differ significantly from the E1 and E2 treatments, the E2 treatment gave the highest seedling vigor, dry matter production rate, and leaf growth rate, and there were no differences in the rice cultivars in the study in all the studied traits, the interactions were not significant in all the studied traits except the leaf growth rate, the treatment E3×V3, and E2×V2 excelled in the leaf growth rate and gave the highest value, while the E4×V2 treatment had the lowest leaf growth rate.

Effect of Brown Manuring and Different Levels of Nutrients on Growth and Yield Attributes of Aerobic Rice (Oryza sativa L.)

A field experiment was conducted during kharif season of 2019 to assess the Effect of brown manuring and different levels of nutrients on growth and yield attributes of aerobic rice (Oryza sativa L.) at Crop Research Centre, Dr Rajendra Prasad Central Agricultural University, Pusa, Bihar. This experiment was conducted in randomized block design (factorial) with sixteen treatment combinations replicated thrice using the rice variety “Abhishek” as a test crop which was planted with a spacing of 20 cm row to row, with the seed rate of 40 kg ha-1. The experimental results indicated that higher values of growth parameters viz. Plant height (109cm), tillers/m2 (355), dry matter production (969g/m2) and crop growth rate (12.2g/m2/day) were observed in rice + brown manuring treatment (B2) as compared to rice without brown manuring (B1) at harvest. While among the nutrient levels, treatment F8- 70 kg/ha phosphorous and 50 kg/ha potassium as split recorded significantly higher growth parameters (tillers/m2, dry matter production and crop growth rate), yield attributes (panicles/m2, grains/panicle), grain yield, while remaining at par with treatment F4 -60 kg/ha phosphorous and 50 kg/ha potassium as split. However, the interaction effect of both the factors did not significantly influence any of the parameters. Further the Aerobic rice cultivation save 40-45 per cent of water as compared to low land cultivation of rice.

Performance of different sources of nitrogen under different establishment methods of rice (Oryza sativa

Currently, conventional fertilizers are used in large quantities to deliver nutrients to crops in India. It may result in soil health decline and fertilizer waste. Different techniques, such as nano fertilizers, are required to address this issue. Therefore, a field experiment was laid out in a farmer's field in the Chidambaram block during the kuruvai season of 2021-22 to determine the "Performance of different sources of nitrogen under different establishment methods of rice." The experiment was carried out in a split-plot design, which included three methods of crop establishment viz., mechanical transplanting, the system of rice intensification (SRI) and conventional transplanting in the main plot, and five nitrogen management methods viz., 100% RDN through urea, 100% RDN through vermicompost, 50% RDN through urea+50% RDN through nano urea, 50% RDN through vermicompost + 50% RDN through nano urea, and 100% RDN through nano urea in sub-plot replicated thrice. The experiment findings demonstrated that among the establishment techniques and nitrogen management practices tested, the system of rice intensification and application of 50% inorganic nitrogen in combination with 50% nano nitrogen was the most productive in terms of plant height (90.29 ,105.39 cm), number of tillers/m2 (337.39, 403.15), dry matter production (10135, 12331 kg/ha) and crop growth rate (10.35, 12.41 g/m2/day) resulting in higher grain (4794, 5972 kg/ha) and straw yield (7216, 8692 kg/ha). Nano fertilizer application promoted the growth and development activity in rice and demonstrated the potential to improve crop production and plant nutrition.

Predicting the effects of climate change on physiological parameters determining wheat yield in 2050 (case study: Golestan Province, Iran)

Climate change is one of the most important threats to food security. Earth's temperature is reported to increase by 1.5 to 4°C by the end of the twenty-first century, compared to the base period (1850-1900), and will continue after 2100. Different models have been used to investigate the effects of climate change on different plant responses, including the exponential downscale statistical model of SDSM. Photosynthesis, respiration, and production are some of the first components to be affected by temperature which are discussed here. This study was aimed to introduce and compare the best interpolation method of main temperatures and precipitation to simulate the rate of photosynthesis, total respiration (total growth and maintenance respiration), and dry matter production of wheat in Golestan Province under climate change. Long-term data of 38 synoptic meteorological stations were used to interpolate the main temperature variables and provide reliable maps. Then, temperature change (ΔT) was used to simulate photosynthesis, total respiration, and dry matter production using the canopy photosynthesis simulation model (Can_Phs). The results clearly showed that by changing the minimum temperature by 1.1 to 3.1°C and the maximum temperature by 2.3 to 4°C, the amount of wheat production in the study area will be affected in 2050. This increase in temperature can reduce the length of the growing season in autumn wheat and limit the duration of intercepting light and capturing other resources, which in turn leads to a decrease in photosynthesis and increased respiration during the growing season.

Growth and Physiological Performance of Barley Plants Produced under Nitrogen Management

This work aimed to evaluate the effect of nitrogen dose management on the growth responses and physiological performance of barley seeds. Two barley cultivars (BRS Brau and BRS Cauê) and four nitrogen doses were used. The experimental design consisted of randomized blocks in a 2 X 4 factorial scheme (cultivars BRS Brau and BRS Cauê x nitrogen doses 120, 150, 180, and 210 kg ha-1). Successive collections of primary data were performed every fourteen days for growth analysis. The analyzed variables were total dry matter, dry matter production and relative growth rate, assimilated partition, and seed electrical conductivity. Increasing nitrogen doses caused a temporal-quantitative difference in growth, partition, and the accelerated aging test of barley seeds. The 150 kg ha-1 N dose resulted in total dry matter over time (Wt) superiority for both evaluated cultivars. The variable dry matter production rate achieved an increase with the 150 kg ha-1 N dose at 70 days after emergence (DAE) for BRS Brau and at 56 DAE for BRS Cauê supporting Wt. The 180 and 150 kg ha-1 N doses increased the relative growth rate for BRS Brau and BRS Cauê.

Extended photoperiods after flowering increase the rate of dry matter production and nitrogen assimilation in mid maturing soybean cultivars

• Extended photoperiods after flowering prolonged reproductive growth. • Vegetative and reproductive biomass increased under extended photoperiods. • Crop growth rate increased, and duration of the growth period was lengthened. • Nitrogen assimilation increased with no change in tissue nitrogen concentration. In soybeans, exposure to non-inductive photoperiods ( i.e ., long or extended days) after flowering triggers a number of responses, including slower development of reproductive structures, enhanced vegetative growth and increased production of flowers. The larger number of flowers under extended photoperiods results in an increase of the number of fruits, which eventually may translate into greater grain yield. The main goal of this work was to assess whether C and N assimilation rates increase in soybeans subjected to long days after flowering. Soybean cultivars NS4619 and NS5019 were planted in the field during the normal planting season in 2016−17 and 2018−19. At flowering, two treatments were imposed: natural (Nat) or extended photoperiods (Ext) in which daylength was prolonged by 4 h with low intensity illumination from light-emitting diode lamps delivering less than 10 μmol m −2 s −1 of photosynthetically active radiation at the top of the canopy. Extended photoperiods prolonged reproductive growth, thereby delaying crop maturity. Growth of the main stem and branches was promoted by Ext, with plants showing greater number of nodes and main stem + branches dry weight at maturity. The number of pods and seeds increased by 69–87 % and 31–76 %, respectively, in Ext, and pod and seed dry weight increased significantly in 2016−17. Averaged over the whole reproductive period, crop growth rate increased under Ext in 2016−17 and 2018−2019. Ext promoted post-flowering vegetative growth more than growth of seeds, therefore harvest index was lower under Ext. The growth increase under Ext was larger if the biomass of abscised leaf blades and petioles was taken into account. Consistently with increased biomass under Ext, nitrogen accumulation by the crop was higher under extended photoperiods, with no dilution effect of N due to increased dry mass. About half of the N in plant tissues derived from biological nitrogen fixation, irrespective of photoperiodic condition, which implied that both, nitrogen fixation and uptake of soil nitrogen increased under long photoperiods. In brief, both the amounts of C and N assimilated by the crop were higher under Ext. Understanding the molecular, biochemical and physiological basis of post-flowering photoperiodic effects might offer clues to increase the yield potential of soybeans.

Adoção de biotecnologias para revegetação mais eficiente por feijão-de-porco e crotalária em rejeito de minério de ferro

Often unable to regenerate naturally, areas degraded by ore tailings must follow measures aimed at their environmental recovery. The revegetation and the use of bio-stimulants can contribute to the improvement of soil fertility leading to increased production of plant biomass and the cycling of nutrients between soil-plant.The objective was to evaluate the dry matter production, accumulation and nutrient export rates by pig beanplants (Canavalia ensiformis) and Crotalaria juncea cv. IAC-KR-1 as a function of the application of humic substances and diazotrophic bacteria. The experiment was conducted in a greenhouseusing iron ore tailings as substrate. An experimental design of random blocks (4x3x2) was used with four repetitions, four doses of humic substances, applied at 3 different times, with or without inoculation of diazotrophic bacteria. The supply of humic substances and mainly the inoculation in both species increased the dry matter production, reaching 70% of the average increase in pig beans. Inoculation in pig bean plants increased the absorption and transfer factor of Fe and P, and reduced the transfer factor of K, Ca and Mg, and in crotalaria plants increased the absorption of Mg, P and Mn, and reduced the absorption of Fe. The high content of Fe in mining tailings culminated in high absorption and mobilization of this element in the roots of the plants as an alternative to minimize toxic effects caused by its excess.

Assessing cloudiness effect on soybean yield in the Southeast Brazil

The solar radiation is one of the most important weather variables for determining the potential yield of agricultural crops. Soybean is the main Brazilian agricultural commodity, with great social and economical importance for the country. It is well recognized that cloudiness is a limiting factor for crop growth rate. Few studies have been conducted to systematically evaluate how much cloud affect soybean yield and none, to our knowledge, is available for tropical soybean. The objective of this paper was to quantify the implications of cloudiness on soybean growth and development in tropical Brazil. To do so, experimental data associated with the simulations of the DSSAT/CROPGRO (DC) model was used, and two treatments were simulated: a) the first used measured solar radiation and b) the second used estimated solar radiation for non-cloud days. Thus, based on the model output variables (growth rate of aerial dry matter, grain yield, specific leaf weight, and light saturation point) and comparing the data with the literature review. We found that simulations exhibited an increase in the dry matter production rate of up to 23%, during days of clear sky, resulting in a yield increase between 26 and 37%. Also, the DC could simulate some adaptation in the plant when the solar radiation changes, like the specific foliar weight and the light-saturated photosynthesis rate.

Vegetation dry matter dynamics along treeline ecotone in Western Himalaya, India

The study aimed to assess dry matter dynamics of forests along treeline ecotone concerning environmental variability, and four representative forests, birch, kharsu oak, Himalayan fir and mixed forest along treeline ecotone (3250–3400 m asl) were selected in Kedarnath Wildlife Sanctuary, Western Himalaya. Temperature, precipitation and humidity data were recorded for complete 3 years (2008–2010). Field inventory for assessment of forest structure and dry matter was carried out in a 200 m transect in each forest along treeline using quadrats of different sizes for tree, shrub and herb layers. The biomass and net primary productivity (NPP) of woody vegetation was estimated using region-specific allometric equations and of the herb layer, by harvesting. Litter quantity and decomposition rates were assessed using litter traps and litter bags, respectively. The dry matter budget of treeline ecotone was represented using a compartment model. The mean annual temperature at treeline was recorded 6.6 ± 0.68 °C with warmest month average temperature of 12.6 ± 1.2 °C. The average forest biomass at ecotone was 33.27 ± 16.97 Mg/0.1 ha, ranged between 8.87 Mg/0.1 ha in open and early successional birch forest to 44.98 Mg/0.1 ha in dense canopy mixed forest. NPP ranged from 1.49 to 2.11 Mg/0.1 ha year−1. The birch forest exhibited the highest efficiency in annual dry matter accumulation in the canopy layer among all forests. The leaf litter decomposition rates (% weight loss) was highest for kharsu oak (74%) after 3 years. The study revealed that Western Himalayan treeline exhibit warmer summer and higher amounts of dry matter storage, production and decomposition rates. These treeline forests showed a higher dry matter assimilation rate and so the potential for carbon sequestration under a warming climate.

Effect of organic manures and bio-fertilizers on growth and yield of senna (Cassia angustifolia Vahl.) cv. Sona

A field experiment was conducted during late kharif season of 2018–2019 at College of Horticulture, Anantharajupeta to evaluate the effect of different organic manures and bio- fertilizers on growth and yield of senna cv. Sona. Vegetative growth parameters like plant height (87.26 cm), number of branches (17.40), dry matter production (0.867 kg m−2) and crop growth rate (15.22 g m−2 d−1) were found maximum by application of 100 per cent recommended dose of nitrogen (RDN) through urea and was found at par with the application of 100% RDN through vermicompost in combination with bio-fertilizers. Number of days required for 50% flowering, total number of leaves, leaf area (cm2), total chlorophyll content (SCMR values) and stem girth were found significantly maximum by application of 100% RDN through vermicompost in combination with biofertilizers and was found at par with 100% RDN through urea. Specific leaf weight and leaf weight ratio were found nonsignificant among the treatments. Cumulative leaf yield was found significantly highest by application of 100 per cent RDN through vermicompost in combination with bio-fertilizers. However, significantly highest leaf yield and pod yield in senna at 115 and 140 DAS was recorded by application of 100% RDN through urea and was found at par with 100% RDN through vermicompost in combination with bio-fertilizers.

Grazing Preference of Dairy Cows and Pasture Productivity for Different Cultivars of Perennial Ryegrass under Contrasting Managements.

Simple SummaryIncreasing soluble sugars in pasture species can lead to an improved nutrient use efficiency in the rumen and a greater digestibility of forage, which in turn might increase pasture intake. However, this improvement in nutritional value must not be at the expense of pasture productivity; the amount of nutrients harvested is a relevant factor in ruminant grazing systems’ efficiency. Therefore, we tested four different cultivars of perennial ryegrass (two selected for greater soluble sugar content and two standard cultivars) submitted to two contrasting managements (one aimed at improving sugar content and one with the opposite intended effect) for their effects on pasture productivity (by cutting herbage every time the plots reached the target number of leaves per tiller, i.e., two or three) and the grazing preference of dairy cows (six cows grazed for up to 5 hours, in an experimental area with three plots for each of the eight treatments) in spring, summer and autumn. We found that high sugar grasses had lower annual dry matter productivity and no preference was shown by cows, although the agronomic management aimed at reducing sugar concentration enhanced crude protein concentration and increased the herbage harvested (greater preference) in the three seasons, and the time spent grazing in autumn.The objective of this study was to evaluate the pasture performance of different cultivars of perennial ryegrass, two “high sugar” and two standard cultivars, under two contrasting agronomic managements (aimed at either decreasing or increasing water soluble carbohydrates concentration), and their effects on the grazing preference of dairy cows. Eight treatments arising from the factorial combination of four cultivars and two managements were randomly applied to 31-m2 plots in three blocks. Pasture dry matter production and growth rate were measured for one year. Three grazing assessments were performed to establish the grazing preferences of six dairy cows in spring, summer and autumn. High sugar cultivars produced less dry matter per hectare than the standard cultivars. Cows consumed more grass and harvested a greater proportion of the pasture under the agronomic management aimed at decreasing sugar concentration, i.e., with a greater nitrogen fertilization rate and under a more frequent defoliation regime, which could be explained by the greater crude protein concentration achieved under this management. The results suggest that the genetic selection for greater levels of sugars was at the expense of herbage yield, and that cows preferred to graze herbage with a greater crude protein level instead of a greater sugar concentration.

Crescimento de plantas e vigor de sementes de feijão em resposta à aplicação exógena de ácido giberélico

The objective of this work was to evaluate the growth and vigor expression of bean seeds from plants submitted to the application of gibberellic acid. The treatments consisted of the application of gibberellic acid in concentrations of zero; 50; 100 and 200 mg.L-1 in the V2 stage. The samples for growth analysis were performed at regular intervals of seven days after sowing, until the plants reached the R9 stage. At each collection, the plants were separated into organs for determination of growth and dry matter partition. In addition, the harvest index, mass of one thousand seeds, number of seeds per plant, insertion of the first pod, length and total dry matter of seedlings were determined. Total dry matter, dry matter production rates and solar energy conversion efficiency are higher in plants submitted to the exogenous application of gibberellic acid. The harvest index as well as the number of seeds per plant present a tendency of reduction with the increase of the gibberellic acid concentration. However, the mass of one thousand seeds tends to be higher in the dose of 50 mg.L-1. The vigor of bean seeds, evaluated by the test of seedling length, is altered with application of gibberellic acid.

Radiation Use Efficiency and Yield Responses of Clonal Tea (Camellia sinensis) to Locations of Production

Tea in Kenya is grown in the high and medium rainfall areas of the Kenyan highlands in east and west of the Rift Valley, at altitudes ranging from 1300 to 2700 m above mean sea level. Variability in responses of tea genotypes to different environments affects the growth, productivity, and quality of tea. The annual receipt of total shortwave radiation received at any site is determined by the latitude and local climate. Within tea growing regions of Eastern Africa, the main receipt of solar radiation varies from 6500–6700 (MJm-2y-1) at Mufindi, southern Tanzania and Kericho, Kenya, (0022’S 350 21’E) to 7400 MJm-2y-1 at Mulanje, Malawi. Seasonal variations in solar radiation within the year also occur and incident solar radiation at high altitudes can exceed 1000Wm-2. However, the net available energy at the surface of a tea canopy reaches only 100Wm-2. Differences in total light penetration occur among tea varieties. The weight of tea shoots in any one harvest depends on the number developing shoot per unit area, their rate of growth and the average weight of shoots at harvest. Yield components of tea are determined by dry matter production and partitioning. The yield of a tea crop is not primarily limited by the production of dry matter, but by the proportion of the total dry matter partitioned into the “economic yield” of harvestable shoots the harvest index (HI; %). Differences in ground cover, total dry matter and dry matter partitioning between clones and between sites have been attributed to the differences in daily intercepted solar radiation which differ between sites. Nevertheless, dry matter production rates have not been determined for the different Kenyan grown clones in the various tea growing regions of Kenya. A study on 12 clones to evaluate the relationships between the intercepted radiation and its derivatives, environmental factors and yields among selected tea clones in different geographical locations, was conducted on a genotype × environment comprising 20 cultivars laid in a randomized complete block design replicated 3 times, at three locations (Kipkebe, Timbilil and Kangaita). The conversion efficiency, the proportion of radiation intercepted by the canopy, extinction coefficient, incident radiation, and temperature, combined were highly and strongly correlated to yield. However, the only altitude was a significant determinant of conversion efficiency. Altitude is a significant determinant of radiation conversion efficiency and through the efficiency of conversion varies with the location it only contributes to the overall locational parameters that determine yield, the strongest determinant being temperature. Harvest index radiation use efficiency can, therefore, be used as a yield predictor in clonal tea breeding programmes.

Soybean growth, solar energy conversion and seed vigour affected by different nitrogen (N) doses

The objective of this study was to evaluate soybean growth, conversion of solar energy and seed vigour of plants cultivated with different nitrogen doses. We carried out experiments using the cultivar BMX Potencia RR belongs to the maturation group 6.7, presenting an indeterminate growth habit. The experimental design was completely randomised with four replications in a 4 x 8 factorial scheme (four nitrogen doses and eight collection periods). In the Vn stage of soybean development, we applied four different nitrogen fertilisation doses, i.e. 0, 25, 50 and 75 Kg N ha-1 in the form of urea (45% of N). We evaluated leaf area (Af), leaf dry mass (Wf), stem (Wc), roots (Wr) and pods (Wv), dry matter production rate (Ct), relative growth rate (Rw), net assimilation (Ea), rate, leaf area ratio (Sa), solar energy conversion factor (ξ), leaf area ratio (Fa) and leaf mass (Fw), dry matter partition between plant structures, seedling emergence (E) and the emergence speed index (IVE) of the seedlings originated from the seeds produced. The experiment was conducted throughout the crop cycle. Nitrogen application positively impacted soybean growth; a nitrogen dose of 50 Kg ha-1 resulted in highest values of Wt. However, plants subjected to 75 Kg N ha-1 reached higher Rw and L values. Nitrogen fertilisation applied in the stage Vn facilitated plant growth, enhanced the conversion of solar energy and resulted in higher seed vigour.

Ecology of Upland Rice Plants and Seeds Subjected to Growth Regulator

The objective of this work is to verify the influence of the plant regulator trinexapac-ethyl on plant growth and physiological quality of upland rice seeds. We used an upland rice genotype, and the growth regulator was the trinexapac-ethyl. The experiment was completely randomized in a 4 × 8 factorial design related to four concentrations of the plant regulator trinexapac-ethyl [0 (without growth regulator), 0.25, 0.50, and 0.75 L c.p. ha-1] and 7 plant collection times [14, 28, 42, 56, 70, 84, 98 days after emergence (DAE)], with four replicates. To determine growth attributes, we evaluated total dry matter, dry matter production rate, relative growth rate, leaf area ratio, leaf matter, leaf area index, solar energy conversion efficiency and partition of assimilates. The physiological quality of the seeds was evaluated based on germination, first germination count, field emergence, emergence speed index and seedling dry matter. Plant growth was affected by the growth regulator. Total dry matter, dry matter production rate and solar energy conversion efficiency decreased, while leaf area index, leaf area ratio and leaf matter increased due to the effects of the growth regulator. The dry matter partition of plants changed in plants subjected to the growth regulator, with a delay in the targeting of assimilates to reproductive organs and a greater allocation to roots at the end of the cycle in plants subjected to the doses 0.50 and 0.75 L·ha-1 of growth regulator. Seed vigor was adversely affected by the growth regulator.

Differences in dry matter production, grain production, and photosynthetic rate in barley cultivars under long-term salinity

Soil salinity is a major environmental stress causing significant loss of crop productivity. Barley (Hordeum vulgare L.) is one of the few field crops that can grow in salt-affected fields and varietal differences in productivity under salinity conditions were known. To clarify the trait most responsible for grain production under salt stress, barley cultivars that were salt tolerant (OUE812) or salt sensitive (OUC613) were grown from seedling to harvest stage in vermiculite containing various concentrations of NaCl. Dry weight of aboveground parts and grain weight decreased significantly with increasing NaCl concentration. The dry weight of the aboveground parts and grain weight decreased more significantly in OUC613 than in OUE812 for plants treated with 150 mM and 200 mM NaCl. A marked reduction in ripening percentage caused significantly decreased grain production in OUC613 as compared with OUE812. In plants treated with 200 mM NaCl, the photosynthetic rate decreased three weeks after starting the NaCl treatment, but a significant difference between cultivars in photosynthetic rate did not appear until seven weeks of NaCl treatment. OUE812 kept a higher photosynthetic rate during ripening than did OUC613 and dry matter production during the period from ripening to harvest was significantly larger in OUE812 than in OUC613. Keeping a higher photosynthetic rate might have contributed to higher grain production in OUE812. Higher ripening percentage and higher rate of photosynthesis during ripening might be target traits in breeding to improve the tolerance of barley to long-term salt stress.

Growth of Wheat Plants Submitted to the Application of the Growth Regulator Trinexapac-ethyl and Vigor of the Produced Seeds

The use of growth regulators in wheat aims to reduce problems caused by the lodging of plants. The aim of this study was to evaluate the growth and vigor expression of wheat seeds treated with a growth regulator and the fertilization of plants to achieve high yields. The cultivar used was OR Topázio, the treatments consisted of the combination of five rates of the trinexapac-ethyl [0 – no application; 200; 400; 600 e 800 mL of the commercial product ha-1] and eight harvesting dates [14, 28, 42, 56, 70, 84, 98 e 112 days after emergence ]. The experimental design was completely randomized, in a factorial scheme 5 x 8 (five rates and eight harvest dates) with four repetitions. The total dry matter, dry matter production rate, relative growth rate, net assimilation rate, conversion efficiency of solar energy, photoassimilate partition, harvest index, and seedling emergence index were evaluated. Allocation of total dry matter, relative growth rate, plant height and harvest index were reduced by the growth regulator, with varied intensity according to the rate applied. The net assimilation rate was reduced in plants subjected to 400, 600 and 800 mL ha-1. The seedling emergence and the speed of emergence index were not affected by the action of the growth regulator.

Photosynthetic responses mediate the adaptation of two Lotus japonicus ecotypes to low temperature

Lotus species are important forage legumes due to their high nutritional value and adaptability to marginal conditions. However, the dry matter production and regrowth rate of cultivable Lotus spp. is drastically reduced during colder seasons. In this work, we evaluated the chilling response of Lotus japonicus ecotypes MG-1 and MG-20. No significant increases were observed in reactive oxygen species and nitric oxide production or in lipid peroxidation, although a chilling-induced redox imbalance was suggested through NADPH/NADP+ ratio alterations. Antioxidant enzyme catalase, ascorbate peroxidase, and superoxide dismutase activities were also measured. Superoxide dismutase, in particular the chloroplastic isoform, showed different activity for different ecotypes and treatments. Stress-induced photoinhibition also differentially influenced both ecotypes, with MG-1 more affected than MG-20. Data showed that the D2 PSII subunit was more affected than D1 after 1 d of low temperature exposure, although its protein levels recovered over the course of the experiment. Interestingly, D2 recovery was accompanied by improvements in photosynthetic parameters (Asat and Fv/Fm) and the NADPH/NADP+ ratio. Our results suggest that the D2 protein is involved in the acclimation response of L. japonicus to low temperature. This may provide a deeper insight into the chilling tolerance mechanisms of the Lotus genus.

コシヒカリ対立遺伝子が光合成速度を高める量的形質遺伝子座(QTL)を集積したタカナリを遺伝背景とする水稲の光合成速度と乾物および子実生産

コシヒカリ対立遺伝子が光合成速度を高める量的形質遺伝子座(QTL)を集積したタカナリを遺伝背景とする水稲の光合成速度と乾物および子実生産

English

Late season crops in planossoil are prone to waterlogging associated with high temperatures that are characteristic of the season, during brief periods of time in early summer. The aim of the present study was to evaluate growth, assimilate partitioning and seed vigor of bean plants subjected to periods of waterlogging and high temperatures during late season. Bean plants of the IPR Tuiuiu genotype were submitted to conditions of soil field capacity and to waterlogging for 8, 16 and 24 h. In order to obtain growth data, plants were collected in regular intervals of seven days until the end of the crop cycle, starting after sowing, dry matter content and leaf area were determined and used to estimate dry matter production, relative growth and net assimilation rates, leaf area index, solar energy conversion efficiency and organs’ dry matter partitioning. Seeds were collected at the end of the developmental cycle and used for seedling emergence test and evaluation of initial growth. The level of stress imposed by waterlogging and high temperatures is time dependent, paralyzing dry matter allocation in bean plants and reducing the conversion efficiency of solar energy. Seeds produced by plants under this stress present low vigor and reduced initial growth. Key words: Phaseolus vulgaris L., stress, dry matter, physiological performance of seed.