N. Trapani
University of Buenos Aires
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Featured researches published by N. Trapani.
Field Crops Research | 1982
A.J. Hall; F. Vilella; N. Trapani; Claudio A. Chimenti
Abstract The effects of exposure to water stress at three developments stages (start of tasseling, start of pollen-shedding, and silking) on the viability of pollen and the dynamics of flowering in maize (Zea mays L.) were examined using a single genotype. Viability was not affected by stress at any stage, but alterations in the dynamics of flowering reduced the number of pollen grains available for pollination of the last ears to silk within the stressed populations. In a second experiment the effects of stress at the start of pollen-shedding on the availability of pollen during the presentation of silks was studied in a set of six cultivars. There was considerable variability between cultivars in the number of pollen grains produced per tassel, and water stress decreased the quantity of pollen grains harvested. There was a strong association between pollen availability and kernel number in the apical ear (as a proportion of control values). Two effects of stress on pollen availability were distinguished: a reduction in the duration of exposure of silks of the apical ear to pollen, and a fall in the rate of pollen production during the period in which receptive silks were present. The relative importance of these effects in determining pollen availability varied with cultivar.
Field Crops Research | 1992
N. Trapani; A.J. Hall; V.O. Sadras; F. Vilella
Abstract Radiation use efficiency (ϵ) values for sunflower were derived using data from periodic determinations of crop aerial or total (aerial + root) biomass and radiation interception in two experiments conducted at Junin and Buenos Aires, Argentina. Analysis showed that three distinct phases, each characterized by a different value of ϵ, could be distinquished. The phases were establishment (0–47 days after emergence ( dae )), rapid growth (47 dae -anthesis) and postanthesis (anthesis-physiologcial maturity). The crops had reached the bud-visible stage and intercepted at least 85% of incident radiation by 47 dae . Efficiency values based on aerial biomass were highest during the rapid growth (ϵrg = 2.4 ± 0.22 g/MJ PAR) phase and lower during the establishment (ϵe = 1.01 ± 0.25 g/MJ PAR) and postanthesis (ϵpa = 1.3 ± 0.15 g/MJ PAR) phases. The differences between ϵpa and ϵrg are attributed to the increased respiration load, high synthesis costs of the oil-rich grains and leaf senescence during grain filling. The value of ϵe was less than of ϵrg even when efficiencies were calculated on the basis of total crop biomass (i.e. including root biomass). Hence, ontogenetic changes in partitioning of biomass between the root and aerial organs do not seem to be the cause of the changes in the value of ϵ. No variations in photosynthetic capacity with leaf position could be found, and it is concluded that the most likely reason for the lower values of ϵe lies in saturation of canopy photosynthesis at less than full sunlight while crop cover is incomplete.
Field Crops Research | 1999
M. López Pereira; N. Trapani; V.O Sadras
We compared the partitioning of dry matter and the oil and protein content in the grain of sunflower (Helianthus annuus L.) cultivars released in Argentina between 1930 and 1995. At anthesis, the fraction of plant dry matter partitioned to leaf and head increased, whereas the fraction in the stem decreased with year of cultivar release. Improved oil yield was related to the increase in: (i) harvest index (grain mass/shoot mass) from about 0.3 to 0.5; (ii) kernel-to-grain ratio from 0.6 to 0.8; and (iii) kernel oil concentration from 58 to 70%. The duration of the period of grain growth as a fraction of season length accounted for half of the variation in harvest index. Kernel oil concentration was negatively associated with protein concentration which dropped from 23 to 13%. Further improvement in partitioning may be possible, including increase in harvest index resulting from enhanced contribution of stored assimilate to grain growth. Owing to the dramatic improvement in partitioning achieved in the last seven decades, however, further increase in yield may need to focus on increasing biomass production.
Photosynthesis Research | 1983
R. A. Sánchez; A.J. Hall; N. Trapani; R.Cohen de Hunau
The dynamics of leaf chlorophyll level, nitrogen content, photosynthesis and stomatal conductance were followed in detail in two cultivars of maize (Zea mays) during a short period of water stress, applied at tasseling, and during the subsequent recovery phase. Plants used in the experiment were grown in sand-nutrient solution culture under field weather conditions. Water stress reduced chlorophyll levels, stomatal conductance and photosynthesis, but the nitrogen content of the leaves was not affected. It is concluded that the stress-induced loss of chlorophyll is not mediated by a lack of nitrogen. Considerable differences were observed between genotypes in the rate of post-stress recovery of chlorophyll level. Recovery, upon rewatering, of stomatal conductance and photosynthesis preceded that of chlorophyll level. Losses of up to 40% of leaf chlorophyll content were insufficient to affect rates of photosynthesis measured at mid-day.
Field Crops Research | 1989
V.O. Sadras; A.J. Hall; N. Trapani; F. Vilella
Abstract Crops of sunflower ( Helianthus annuus L.) were grown in a coarse loam Typic Hapludoll to characterize the spatial and temporal development of the root systems, the relationships between root systems and leaf area, and their responses to plant population. Two experiments were carried out, one involving single plant population, the other (using a different cultivar) covering the range of population from 2.04 to 5.10 plants m −2 . The trench profile method was used to estimate root density in the row and in the inter-row space. These data were used to estimate root depth and root length on a ground-area basis. The former was defined as the depth which contained 90% of the total root system below the 0-0.2-m layer ( D 90 ). Rooting depth ( D 90 ) and total root length increased up to anthesis and root length decreased thereafter. Plant population had negligible effects on ( D 90 ). The inter-row space was colonized by roots at a slower rate than the within-row space, and after anthesis loss of roots from the former space took place more rapidly. A single allometric function fitted the seasonal changes in the relationship between D 90 and leaf area per plant for all crops. The dynamics of roots in the plough and below-plough layers showed different responses to population. Low-population crops had the highest and lowest peak values of root length in the plough and below-plough layers, respectively. In both layers, roots of low-population crops continued to grow until later in the season. Root length and leaf area per plant decreased markedly with population but on a ground-area basis these effects were small. These morphological responses to population are analyzed in relation to their possible effects on crop water use.
Field Crops Research | 1999
M. López Pereira; N. Trapani; V.O Sadras
Abstract Historic sets of sunflower ( Helianthus annuus L.) cultivars released in Argentina between 1930 and 1995 were compared in two field experiments. Breeding and selection shortened cycle length: most of the reduction came from a reduction in time to anthesis, which together with a stable time from anthesis to maturity increased the proportion of the growing cycle given to grain growth. Shoot biomass at maturity was unrelated to year of cultivar release but a greater portion was produced after anthesis. The ratio between leaf area index duration from anthesis to maturity and grain number was taken as a measure of source-to-sink ratio; this ratio was smaller in hybrids than in open-pollinated cultivars. Variation in both the amount of oil per grain and grain mass were small in comparison with the variation in source-to-sink ratio indicating that additional carbon may have attenuated the effects of less leaf area duration per grain. Owing to the relative stability of the amount of oil per grain and the reduction in grain mass, the grain oil concentration increased despite the drop in source relative to sink. Further yield improvement will mostly depend upon the increase in the supply of substrates to fill the grain provided grain size is not restricted by events occurring before anthesis.
Field Crops Research | 1994
N. Trapani; A.J. Hall; Francisco J. Villalobos
Abstract A simple framework for describing the partitioning of biomass among the organs (root, stem, laminae, head) of sunflower plants between emergence and anthesis as been developed using data from experiments in which adequate water and nitrogen supplies were assured. It was hypothesized that organ partitioning coefficients (the slope of the organ weight: total weight relationship) remained constant during phenologically defined phases of crop development. A non-linear optimization routine was used to define organ partitioning coefficients and the values of total plant weight at which changes in partitioning took place. It proved possible to relate these values to defined stages of plant development, namely bud visible and commencement of rapid head growth. The dynamics of partitioning to the stem could be described by two coefficients applying to the emergence-bud visible and bud visible-anthesis phases, respectively. Complementary changes in the coefficients for leaf laminae and fine roots took place at the bud visible stage. Once rapid growth of the inflorescence had become established, further changes in partitioning to roots and laminae, but not to stem, took place. Values of the coefficients for each organ changed only slightly between experiments (three) and cultivars (five), in spite of substantial variations, between data sets, of total plant weight at anthesis and, to a lesser extent, in the timing of the anthesis and bud visible stages. A satisfactory description of organ biomass dynamics was obtained when this descriptive framework was tested against data obtained in an independent experiment.
Field Crops Research | 1984
A.J. Hall; Claudio A. Chimenti; N. Trapani; F. Vilella; R.Cohen de Hunau
Abstract Thirteen maize ( Zea mays L.) genotypes were evaluated for variability with respect to seedling traits reportedly associated with tolerance to water stress. Significant variability was found within this set of cultivars for chlorophyll loss under thermal stress, loss of intracellular electrolytes under thermal and desiccation stresses, and proline accumulation in response to desiccation. These attributes were not mutually correlated in the genotypes examined. A sub-set of seven genotypes was grown in a sand-nutrient solution culture in the field and subjected to stress at tasseling for about eight days. Yield was significantly reduced in all cultivars, but the magnitude of the reduction was variable. Relative kernel number of the uppermost ear (the major yield-determining factor in most cultivars) was strongly associated with duration of exposure to pollen of the same ear. Relative spikelet number of the uppermost ear was significantly reduced intwo cultivars by stress, but this response appeared to be independent of mean exposure to pollen. Relative spikelet number was associated with plant-leaf area: root weight ratio at tasseling. No association was found between seedling traits and relative yield, additional yield-related responses or other, presumably less complex, responses to stress such as loss of leaf area and fall in chlorophyll content.
Communications in Soil Science and Plant Analysis | 2007
Patricia I. Giménez; Daniel Sorlino; N. Trapani
Abstract The objective of this work was to compare and characterize the response to nitrogen (N) supply of a textile and an oilseed cultivar of flax (Linum usitatissimum L.). The dynamics of growth, biomass partitioning, growth rates, and leaf area evolution and duration of the cultivars Omega (oilseed) and Diane (textile) were compared under three rates of N supply. Plants were grown in pots in the field with nil (N1), 2.5 (N2), and 5 g N per pot (N3); N2 and N3 doses were divided into five applications. Shoot biomass of N2 and N3 treatments was similar in both cultivars and significantly higher than in N1. Partitioning of biomass was unaffected by N treatment but showed contrasting patterns between cultivars. The oilseed cultivar produced 30–42% more reproductive biomass and 18–30% less stem biomass than its textile counterpart. Differences between cultivars in these traits increased with increasing N rate. Maximum growth rates per plant concentrated around 1572°Cd after sowing (fructification). Faster leaf senescence after flowering contributed to the lower leaf area and leaf biomass of the textile cultivar. The availability of N at different specific moments of the plant cycle would be useful to improve the growth of organs of economic interest. Results can also provide useful information to future nutrition models and breeding programs in textile and oilseed flax.
Journal of Natural Fibers | 2005
María Belén Agosti; Daniel Sorlino; N. Trapani
Abstract There are not enough antecedents about the effect of a decrease in photosynthesis on flax stem growth and elementary fiber length. Therefore, plots sowed with cultivar Diane were shaded with nets that intercepted 70% of photosynthetically active radiation. The nets were placed at three stages of the growth period: S1: 575°Cd (height: 25 cm), S2: 854°Cd (height: 54 cm), and S3: 1304°Cd (height: 84 cm). These applications resulted in stems shadowed only in the parts, which grew during the treatment. Additionally, control plots without shadows during the entire cycle (S0) were grown. In every treatment the production of fiber was quantified, and a harvest index (HI = fiber biomass obtained/stems biomass produced) was calculated. Fiber quality was also evaluated using elementary fiber length. The harvest index was bigger in control plants than shadow plants. The length of elementary fiber of the shadow treatments S1, S2, and S3 was 4.28 cm, 3.76 cm, and 3.02 cm, respectively, whereas the adjacent portions to the shaded one in each treatment had a length fiber increase of 21%, 34%, and 37%, respectively. In the same portions, S0 had fiber lengths of 4.94, 4.45, and 3.82 cm, respectively. The trend observed in all the shaded treatments showed a decrease of elementary fiber length. The fiber length in the adjacent portions to the shaded ones was not conditioned by the shadow treatment received. These results allow relating fiber quality with stresses generated by meteorological events that take place during the growth of the stem.