Stefano Bona

A comparison of root characteristics in relation to nutrient and water stress in two maize hybrids

Root responses of maize (Zea mays L.) to limited nutrients and water availability were evaluated in two highly productive full-season hybrids, DK585 and Santos (Dekalb — Monsanto), in laboratory, pot and field tests. In the laboratory, under optimal nutrient and water supply, seedlings of DK585 had higher growth (leaves and roots). Under nitrate or sulphate deprivation, DK585 showed better ability in adapting its root/shoot ratio to stress conditions, whereas Santos showed less plastic behaviour. This morphological trait of DK585 was associated with higher sulphate and constitutive nitrate influxes. In pot trials (plants with four to five leaves), DK585 maintained a high transpiration level to very low values (around 0.2) of FTSW (fraction of transpirable soil water), whereas Santos showed a higher response to soil drying. The latter reduced the rate of transpiration starting from a FTSW of about 0.6. In the open field (trial in 2000, Legnaro, NE Italy), in conditions of fluctuating combined water and nitrogen stress, DK585 at flowering reached greater root length density (RLD) than Santos in deep layers (50–100-cm interval depth) of positions further from the plant. However, in these conditions, the yield of DK585 was found to be only slightly higher than that of Santos (8.88 vs. 8.49 t ha.−1 d.w.). An overall evaluation of the two hybrids indicates the more conservative strategy towards limited water and nutrient resources in Santos, and a greater tendency towards stress avoidance in DK585.

Oil crops for biodiesel production in Italy

There is an energy advantage in methylester production using sunflower, rapeseed and soybean as crop suppliers of energy, the process being practicable in terms of technique and energy gain. The three oilseed crops considered in this work are suitable for considerable reduction of inputs with consequent energy savings and low environmental impact. Nevertheless, because of its low arable surface area, the number of available hectares being static, Italy is oriented towards intensive management. As a consequence, optimisation of cropping techniques is the main strategy to be pursued for higher crop yields for methylester production.

Nitrogen accumulation and nodule activity of field-grown ‘Jackson’ soybean in response to water deficits

Abstract Substantial evidence has accumulated that N 2 fixation in soybean ( Glycine max Merr.) is much more sensitive to drying soil than is leaf gas exchange and plant mass accumulation. In contrast, the soybean cultivar Jackson in controlled environments has been found to have N 2 fixation sensitivity to drying soil that is approximately equivalent to the sensitivity of leaf gas exchange. This study was undertaken to determine if Jackson behaved in a similar way under field conditions. N 2 fixation activity was measured by in situ acetylene reduction rates and N accumulation in shoots. Leaf gas exchange was measured as stomatal conductance and shoot mass accumulation. All measures in this field study indicated that N 2 fixation in Jackson decreased in response to soil drying in about the same proportion as leaf gas exchange. These results with Jackson were in contrast to those with the cultivar Biloxi in which N 2 fixation was decreased to a greater extent by drought than was leaf gas exchange.

Ureide concentration of field‐grown soybean in response to drought and the relationship to nitrogen fixation

Abstract Ureides accumulate in soybean (Glycine max [L.] Merr.) petioles during drought under greenhouse conditions despite decreased N2 fixation and ureide production. Field experiments with water‐deficit treatments were established to examine the possibility of ureide accumulation under natural drought‐stress conditions. Tissue ureide concentration of drought tolerant ‘Jackson’ were compared with either ‘Hutcheson’ or ‘Biloxi’. For mild water‐deficit conditions, petiole ureide levels were greater than a well‐watered treatment at ten sampling dates for Hutcheson compared to three dates for Jackson. At only two dates were there significant differences between genotypes in petiole ureide concentration, in which case petiole ureide concentration of Hutcheson was greater than Jackson. Under more severe water‐deficit conditions, there were greater and more consistent increases in petiole ureide concentration for Jackson and Biloxi. Jackson, however, had lower petiole ureide concentration than Biloxi throughou...

An approach to minirhizotron root image analysis

Minirhizotrons speed up research on root demography, but image quality often hampers standardization of the image processing method. A simple procedure working on the blue band of colour images was tested on fibrous roots of sugarbeet (Beta vulgaris var. saccharifera). With respect to green and red, the blue band allows better detection of roots when their luminance is very similar to that of the background. The method makes use of an exponential algorithm of contrast stretching, which takes luminance frequency distribution into account. Based on a single threshold level, the procedure includes skeletonization. A minimum segment length was adopted to discriminate roots from extraneous objects. Although a specific minimum root length (MRL) value was calculated for each soil type, results show that a single value can be applied, indicating that this method can be profitably used for processing large samples of images.

Analysis of root images from auger sampling with a fast procedure: a case of application to sugar beet

Manual line-intersect methods for estimating root length are being progressively replaced by faster and more accurate image analysis procedures. These methods even allow the estimation of some more root parameters (e.g., diameter), but still require preliminary labour-intensive operations. Through a task-specific macro function written in a general-purpose image analysis programme (KS 300 — Zeiss), the processing time of root images was greatly reduced with respect to skeletonisation methods by using a high-precision algorithm (Fibrelength). This has been previously proposed by other authors, and estimates length as a function of perimeter and area of the digital image of roots. One-bit binary images were acquired, aiming at large savings in computer memory, and automatic discrimination of roots against extraneous objects based on their elongation index (perimeter2/area), was performed successfully. Of four tested spatial resolutions (2.9, 5.9, 8.8, 11.8 pixel mm−1), in clean samples good accuracy in root length estimation was achieved at 11.8 pixel mm−1, up to a root density of 5 cm cm−2 on the scanner bed. This resolution is theoretically suitable for representing roots at least 85 Am wide. When dealing with uncleaned samples, a thick layer of water was useful in speeding up spreading of roots on the scanner bed and avoiding underestimation of their length due to overlaps with organic debris. A set of fibrous root samples of sugar beet (Beta vulgaris var. saccharifera L.) collected at harvest over two years at Legnaro (NE Italy) was analysed by applying the above procedure. Fertilisation with 100 kg ha−1 of nitrogen led to higher RLD (root length density in soil) in shallow layers with respect to unfertilised controls, whereas thicker roots were found deeper than 80 cm of soil without nitrogen.

Fibrous root turnover and growth in sugar beet (Beta vulgaris var. saccharifera) as affected by nitrogen shortage

The root system of plants is subject to fast cycles of renewal and decay within the growing season. In water and/or nutrient stress conditions, this turnover may become strategic for plant survival and productivity, but knowledge about its mechanisms is still insufficient. In order to investigate the effects of nitrogen fertilization on growth and turnover of sugar beet roots, an experiment was carried out over two growing seasons in northern Italy with two levels of N supply (0, 100 kg ha−1). Biomass production and partitioning were followed during growth, and fibrous root dynamics were inspected by means of computer-aided procedures applied to minirhizotron images.

Assessment of transplanting date influence on processing tomato (Lycopersicon esculentum Mill.) production using the Cropping System Model (CSM)-CROPGRO-Tomato simulation model A case study for northeastern Italy

Italy produces more than 6.4 million tons of tomatoes annually from an area of 117100 ha at an average yield of 54506.4 kg ha-1 (FAO, 2009). This represents 21.4% of the I TALIAN processed tomato has a major dominance at the global level but few studies have been conducted using a cropping systems analysis approach for this crop.The objective of this research was to evaluate the Cropping System Model (CSM)-CROPGRO-Tomato of the DSSAT (Decision Support System for Agrotechnology Transfer) software with experimental data obtained from field studies conducted in Legnaro, northeastern Italy in 2009 and 2010. The experiment encompassed four transplanting dates with ten-day intervals from 22nd March (TD1, 2, 3, and 4), and two processing tomato varieties (Augusto F1 (De Ruiter), and NPT 63 (S & G)) comparing mulched and non-mulched plots. A comparison of yield for the different transplanting dates showed that earlier transplanting increased yield for both varieties, there was a variation in yield between varieties in both years. Calibration of CSM-CROPGRO-Tomato model using nonmulched data of 2009 showed that index of agreement (d-Stat) between observations and model simulation for different parameters (total dry matter, fruits fresh and dry weight, vegetative dry matter, number of fruits, harvest index and leaf area index) using both varieties ranged from 0.562 to 0.964 at TD1, from 0.915 to 0.992 at TD2, from 0.566 to 0.990 at TD3, and from 0.733 to 0.998 at TD4. Values of d-Stat for model calibration were lower for leaf area index, which ranged from 0.511 to 0.924. Model calibration using TD1 gave acceptable simulation, whereas it was quite high with the other transplanting dates. CSM-CROPGRO-Tomato model could be used as a decision-making tool helping in regional short term plans.

Is the root system the key to higher nitrogen uptake in rapeseed

The recently commercialised rapeseed CHL (composite hybrid lines) are reported to give an average increase of about 15% in grain yield compared with ‘old’ varieties in normal growing conditions in France. In Italy, this observation has not been confirmed, since CHL Synergy and a good-yielding variety Ceres generally have similar yields (average of 12 field trials). However, several differences in morphological and physiological characters have been identified in the two genotypes, especially at root level. Both shoot biomass and the amount of shoot nitrogen in Synergy were slightly higher compared with Ceres for most of the growing season, until the end of winter. As regards the root system, Synergy shows evident hybrid vigour, having faster growth and, especially in early stages, greater weight and total length than Ceres, together with higher specific root length. These traits are a prerequisite for the uptake of greater amounts of nitrogen, which may eventually be leached. Although an increase in plant density led to higher root length density in the first soil layer (0–30 cm) for both varieties, nitrate leaching of Synergy exceeded that of Ceres at the high plant density, thus indicating that this hybrid is more sensitive to competition for nitrogen uptake. The increase in nitrate uptake rate per unit root length (V max) found for the hybrid compared with the ‘old’ variety was accompanied by an unfavourable increment of affinity (1/K m ), which may be responsible of a loss of efficiency at high plant density. The morphological and physiological modifications of the hybrid seem to be more useful for reducing nitrogen leaching during winter rather than for increasing grain yield.