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Search Results: 1 - 10 of 11284 matches for " Nereu Augusto;Bellé "
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Vernaliza??o afeta a mobiliza??o de reservas de a?úcares e nitrogênio e a emergência de plantas de lírio (Lilium longiflorum thunb.) ?snow queen?
Nardi, Claudia;Buriol, Galileo Adeli;Bellé, Rogério Ant?nio;Streck, Nereu Augusto;Schuh, Mariangela;
Ciência Rural , 2004, DOI: 10.1590/S0103-84782004000400009
Abstract: in order to evaluate the response of effective vernalization days on the soluble sugar and total nitrogen contents and the emergence of lilium longiflorum plant shoots, cv ?snow queen? bulbs were kept under different vernalization temperatures and periods of treatment under vernalizing temperatures, and cultivated in a plastic greenhouse after the vernalization. the experiment was carried out at the universidade federal de santa maria, rs, in two seasons: from 03/20/02 to 11/05/02 and from 12/05/02 to 05/15/03. the treatments were 0, 9, 11, 14, 19, 23, 28, 29, 34, 38, 42, 45 and 56 effective vernalization days, calculated with a beta response function to temperature. the soluble sugar and total nitrogen contents, and the duration of the planting-emergence (p-m) phase were determined. the vernalization promoted the mobilization of sugar and nitrogen reserves, which is important for the nutrition of the emergence of the shoot. the increasing number of the effective vernalization days reduced the duration of the p-e phase. bulbs treated under temperatures of 10oc for 6 to 8 weeks of storage (34 and 45dv), had the shortest duration of the p-e phase.
Estimating leaf appearance rate and phyllochron in safflower (Carthamus tinctorius L.)
Streck, Nereu Augusto;Bellé, Rogério Antonio;Rocha, Edileusa Kersting da;Schuh, Mariangela;
Ciência Rural , 2005, DOI: 10.1590/S0103-84782005000600036
Abstract: safflower may be an interesting option for the flower market, either as fresh or dried cut flower. estimating the leaf appearance rate and the phyllochron (the time interval between the appearance of successive leaves) is important for calculating the number of emerged leaves (nl) on the plant, which is an excellent measure of plant development. the objective of this study was to estimate the leaf appearance rate and the phyllochron in safflower (carthamus tinctorius l.). an experiment was conducted in santa maria, rs, brazil, inside an 8 x 15m plastic greenhouse. sowing was on 03 october 2003 and emergence was on 08 october 2003. the experimental design was a randomized complete block design with three replications. the main stem nl was measured twice a week from 24 october 2003 to 15 november 2003 in four plants per replication. daily growing degree days above a base temperature (5°c) and accumulated thermal time (tt) were calculated. the nl was linearly regressed against tt. the angular coefficient of the linear regression is the lar (leaves/ °c day) and the phyllochron (°c days/leaf) was estimated by the inverse of the angular coefficient of the linear regression. the lar was 0.0467 ± 0.0203 leaves/ °c day and the phyllochron was 25.5 ± 14.6°c days/leaf.
Estimating leaf appearance rate and phyllochron in safflower (Carthamus tinctorius L.)
Streck Nereu Augusto,Bellé Rogério Antonio,Rocha Edileusa Kersting da,Schuh Mariangela
Ciência Rural , 2005,
Abstract: Safflower may be an interesting option for the flower market, either as fresh or dried cut flower. Estimating the leaf appearance rate and the phyllochron (the time interval between the appearance of successive leaves) is important for calculating the number of emerged leaves (NL) on the plant, which is an excellent measure of plant development. The objective of this study was to estimate the leaf appearance rate and the phyllochron in safflower (Carthamus tinctorius L.). An experiment was conducted in Santa Maria, RS, Brazil, inside an 8 x 15m plastic greenhouse. Sowing was on 03 October 2003 and emergence was on 08 October 2003. The experimental design was a randomized complete block design with three replications. The main stem NL was measured twice a week from 24 October 2003 to 15 November 2003 in four plants per replication. Daily growing degree days above a base temperature (5degreesC) and accumulated thermal time (TT) were calculated. The NL was linearly regressed against TT. The angular coefficient of the linear regression is the LAR (leaves/ degreesC day) and the phyllochron (degreesC days/leaf) was estimated by the inverse of the angular coefficient of the linear regression. The LAR was 0.0467 ? 0.0203 leaves/ degreesC day and the phyllochron was 25.5 ? 14.6degreesC days/leaf.
Vernaliza??o afeta o filocrono em lírio
Schuh, Mariangela;Streck, Nereu Augusto;Nardi, Claudia;Buriol, Galileo Adeli;Bellé, Rogério Ant?nio;Brackmann, Auri;
Bragantia , 2005, DOI: 10.1590/S0006-87052005000100003
Abstract: an experiment was carried out to verify the effect of vernalization period on the phyllochron (time interval between the appearance of two successive leaves) in lily (lilium longiflorum thunb), cv. 'snow queen'. the trial was conducted at santa maria, rs, brazil. treatments were bulbs stored at vernalizing temperatures of -0.5, 4, and 10oc during periods of 2, 4, 6 and 8 weeks. control treatment was unvernalized bulbs. bulbs were planted inside a plastic greenhouse on december 05, 2002, and crop development was evaluated throughout the growing season. phyllochron for each treatment was estimated as the inverse of the slope of the linear regression relating leaf number and accumulated thermal time above 1oc after emergence. results showed that the phyllochron is affected by vernalization. unvernalized plants and plants with low vernalization treatments had greater phyllochron values compared to completely vernalized plants. plants vernalized with 30 or higher effective vernalization days had a phyllochron value around 25 oc days/leaf. this phyllochron can be used as a reference when vernalized bulbs are used in commercial croppings.
Crescimento, desenvolvimento e retardamento da senescência foliar em girassol de vaso (Helianthus annuus L.): fontes e doses de nitrogênio
Fagundes, Joelma Dutra;Santiago, Gisele;Mello, Anderson Machado de;Bellé, Rogério Ant?nio;Streck, Nereu Augusto;
Ciência Rural , 2007, DOI: 10.1590/S0103-84782007000400011
Abstract: sunflower is the fourth oil grain crop grown worldwide and some genotypes are used with ornamental purpose as cut and pot-grown flower. the objective of this study was to evaluate the effect of different sources and rates of nitrogen on some growth and developmental parameters, and on the delay of leaf senescence in pot-grown sunflower. an experiment was carried out inside a greenhouse in santa maria, rs, brazil. treatments were: urea, ammonium nitrate and calcium nitrate at rates of 0, 50, 100 and 150mg l-1 of n in the fertigation solution, with two weekly applications. the experiment was a two-factorial (sources and rates of n) in a completely randomized design with six replications. each replication was a number 15 pot (1.5l, 15cm height) with one plant/pot. the variables analyzed were: final leaf number, final plant height, percentage of senescent leaves at selling stage and at the end of vase life, total leaf area per plant, phyllochron, and the thermal time from emergency to visible bud and from emergency to selling stage. the n source influences leaf area of pot-grown sunflower, with urea being recommend for higher leaf growth. the rate of around 100mg l-1 of n applied twice a week through fertigation promoted desirable characteristics for commercialization such as earliness and delay of leaf senescence.
A generalized nonlinear tempeature response function for some growth and developmental parameters in kiwifruit (Actinidia deliciosa (A. Chev.) C. F. Liang & A. R. Ferguson)
Streck, Nereu Augusto;
Ciência Rural , 2003, DOI: 10.1590/S0103-84782003000200012
Abstract: temperature is a major factor that affects metabolic processes in living organisms. thermal time has been widely used to account for the effects of temperature on crop growth and development. however, the thermal time approach has been criticized because it assumes a linear relationship between the rate of crop growth or development and temperature. the response of the rate of crop growth and development to temperature is nonlinear. the objective of this study was to develop a generalized nonlinear temperature response function for some growth and developmental parameters in kiwifruit (actinidia deliciosa (a. chev.) c. f. liang & a. r. ferguson). the nonlinear function has three coefficients (the cardinal temperatures), which were 0oc, 25oc, and 40oc. data of temperature response of relative growth rate, relative leaf area growth, net photosynthesis rate, and leaf appearance rate in kiwifruit (female cv. hayward) at two light levels, which are from published research, were used as independent data for evaluating the performance of the nonlinear and the thermal time functions. the results showed that the generalized nonlinear response function is better than the thermal time approach, and the temperature response of several growth and developmental parameters in kiwifruit can be described with the same response function.
A temperature response function for development of the chrysanthemum (Chrysanthemum x morifolium Ramat.)
Streck, Nereu Augusto;
Ciência Rural , 2004, DOI: 10.1590/S0103-84782004000100008
Abstract: developmental models can help growers to decide management practices, and to predict flowering and harvest time. currently, a double exponential function is proposed as a generalized temperature response function for chrysanthemum. this function is not the most appropriate because its parameters lack biological meaning. the objective of this study was to develop a nonlinear temperature response function of chrysanthemum development that has parameters with biological meaning. the proposed function is a beta function with three parameters, the cardinal temperatures (minimum, optimum, and maximum temperatures for development), which were defined as 0, 22, and 35oc. published data of temperature response of development of three cultivars, which are independent data sets, were used to test the performance of the double exponential function and the beta function. results showed that the beta function is better than the double exponential function to describe the temperature response of chrysanthemum development.
A temperature response function for modeling leaf growth and development of the African violet (Saintpaulia ionantha Wendl.)
Streck, Nereu Augusto;
Ciência Rural , 2004, DOI: 10.1590/S0103-84782004000100009
Abstract: response functions used in crop simulation models are usually different for different physiological processes and cultivars, resulting in many unknown coefficients in the response functions. this is the case of african violet (saintpaulia ionantha wendl.), where a generalized temperature response for leaf growth and development has not been developed yet. the objective of this study was to develop a generalized nonlinear temperature response function for leaf appearance rate and leaf elongation rate in african violet. the nonlinear function has three coefficients, which are the cardinal temperatures (minimum, optimum, and maximum temperatures). these coefficients were defined as 10, 24, and 33oc, based on the cardinal temperatures of other tropical species. data of temperature response of leaf appearance rate and leaf elongation rate in african violet, cultivar utah, at different light levels, which are from published research, were used as independent data for evaluating the performance of the nonlinear temperature response function. the results showed that a generalized nonlinear response function can be used to describe the temperature response of leaf growth and development in african violet. these results imply that a reduction in the number of input data required in african violet simulation models is possible.
Climate change and agroecosystems: the effect of elevated atmospheric CO2 and temperature on crop growth, development, and yield
Streck, Nereu Augusto;
Ciência Rural , 2005, DOI: 10.1590/S0103-84782005000300041
Abstract: the amount of carbon dioxide (co2) of the earth′s atmosphere is increasing, which has the potential of increasing greenhouse effect and air temperature in the future. plants respond to environment co2 and temperature. therefore, climate change may affect agriculture. the purpose of this paper was to review the literature about the impact of a possible increase in atmospheric co2 concentration and temperature on crop growth, development, and yield. increasing co2 concentration increases crop yield once the substrate for photosynthesis and the gradient of co2 concentration between atmosphere and leaf increase. c3 plants will benefit more than c4 plants at elevated co2. however, if global warming will take place, an increase in temperature may offset the benefits of increasing co2 on crop yield.
Do we know how plants sense a drying soil?
Streck, Nereu Augusto;
Ciência Rural , 2004, DOI: 10.1590/S0103-84782004000200039
Abstract: the reduction of crop growth and yield in dry areas is largely due to stomatal closure in response to dry soil, which decreases photosynthesis. however, the mechanism that causes stomatal closure in a drying soil is a controversial issue. experienced and respected plant physiologists around the world have different views about the primary sensor of soil water shortage in plants. the goal of this review is to present a chronological synthesis about the evidence of the possible candidates for the mechanism by which plants sense a drying soil. hydraulic signals in the leaves as the mechanism that causes stomatal closure dominated the view on how plants sense a drying soil during the 70?s and the early 80?s. in the middle 80?s, studies suggested that stomatal conductance is better correlated with soil and root water status than with leaf water status. thus, chemical signals produced in the roots dominated the view on how plants sense a drying soil during the late 80?s and early 90?s. during the second half of the 90?s, however, studies provided evidence that hydraulic signals in the leaves are still better candidates for the mechanism by which plants sense a drying soil. after more than 60 years of studies in plant-water relations, the question raised in the title still has no unanimous answer. this controversial issue is a good research rationale for the current generation of plant physiologists.
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