Remote-sensing techniques, in particular, multispectral visible and infrared (IR) reflectance, can provide Correlations between plant canopy reflectance and aboveground an instantaneous, nondestructive, and quantitative asbiomass can possibly be used for early prediction of crop yield. Field experiments were conducted in 1998 and 1999 on two soil types to sessment of the crop's ability to intercept radiation and assess whether measurements of canopy reflectance at given stages photosynthesize (Ma et al., 1996). The input of reflecof development could be used to discriminate high from low potential tance into yield production models has been shown to yields among genotypes with known differences in potential grain improve yield estimates (Clevers et al., 1994; Clevers, yield and whether a consistent relationship between yield and canopy 1997). Colwell (1956) was the first to use aerial IR phoreflectance could be used for screening and predicting soybean [Glytographs to monitor plant disease in the field. The cine max (L.) Merr.] yield in a variety trial. A 3-by-42 factorial experiamount of reflectance in the near IR (NIR) range ( ϭ ment, arranged in a randomized complete block design with three 700-1300 nm) is determined by the optical properties replications, was used on each soil type for both years. Three populaof the leaf tissues: their cellular structure and the air-cell tion densities (25, 50, and 75 seeds m Ϫ2 ) represented low, optimum, wall-protoplasm-chloroplast interfaces (Kumar and Silva, and high levels. Forty-two historical varieties represented nearly six decades (1934-1992) of soybean yield improvement in Canada. Can-1973). These anatomical characteristics are affected in opy reflectance was measured with a hand-held multispectral radiome-turn by environmental factors such as soil water and/or ter on three sampling dates (approximately R2, R4, and R5 stages) nutrient status (Gausman et al., 1969; Thomas et al., for each site. Grain yield at harvest was measured. Soybean grain yield 1971; Blackmer et al., 1994), soil salinity (Gausman and was highly positively correlated with canopy reflectance, expressed as Cardenas, 1968), and leaf age (Gausman et al., 1970).normalized difference vegetation index (NDVI), at all sampling dates. Reflectance in the visible red (R) range ( ϭ 550-675 Regression analyses showed a positive relationship between NDVI nm) has been used to estimate leaf chlorophyll and and grain yield, with R 2 up to 0.80 (P Ͻ 0.01) and progressive imcarotenoid (Benedict and Swidler, 1961; Thomas and provement from R2 to R5 stages. Population density did not affect Oerther, 1972;Filella et al., 1995) levels and, by extenthe yield-NDVI relationship at the development stages studied. Our sion, the photosynthetic capability of the crop. data suggest that canopy reflectance measured nondestructively between R4 and R5 stages adequately discriminates high-from low-The use of NIR or R spectral bands singly does not yielding genotypes and provides a reliable, fast, repeatable indicator account f...

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1983), Sinoquet (1989), and Sinoquet and Bonhomme (1992), among others. However, to date, measured two-The amount and distribution of leaf area and leaf angles in a crop dimensional leaf area and leaf angle data have not been canopy determine how photosynthetically active radiation (PAR) is intercepted and consequently influences canopy photosynthesis and incorporated into a light interception-canopy photosynyield. Factors such as plant shape, plant populations, and row width thesis model. will affect these leaf distributions and can occur in an almost infinite Two-dimensional aspects of light interception are parnumber of different combinations. To supplement experimentation, ticularly important in mid-to short-season production a mathematical model was developed to use measurements of leaf areas where leaf area index is rarely in excess of that area and leaf angles in two dimensions (with height and across the required to maximize canopy light interception. Develrow) to calculate PAR interception and canopy photosynthesis. Maize opment of new phenotypes for these production areas, (Zea mays L.) hybrids with phenotypic differences were planted at including leafy and leafy-reduced stature (Dwyer et al., several plant populations to produce a wide range of two-dimensional 1995b; Begna et al., 1997; Modarres et al., 1997), has leaf area and leaf angle patterns. The extreme phenotypes, leafy and required reassessment of optimum plant populations reduced stature, were included to vary plant height and number of leaves above the ear. Measurements of average PAR at various levels and planting patterns to maximize production. The obwere made in seven different canopies and compared with calculations jectives of this study were to develop methods to quanfrom the model (R 2 of 0.68 and 0.92 for two sets of data). As well, tify two-dimensional leaf area distribution and to use measurements of PAR at 20-cm increments on transects perpendicular this distribution to calculate light interception and canto the row were made in three canopy types at three levels and opy photosynthesis. This methodology was used to charcompared with theoretical calculations (R 2 ϭ 0.74). A simple numeriacterize the two-dimensional distribution of leaf area cal experiment was run to demonstrate the utility of the model where of maize hybrids with contrasting architecture and to daily canopy photosynthesis was calculated for two row widths and compare calculations of light penetration into these canseven plant types. One result was that depending on row widths, opies with measurements. We also used the theory to plants with very upright leaves can have both the smallest and largest calculate PAR flux densities on leaf surfaces, which daily canopy photosynthesis.

Despite the importance of the gastronomic experience for tourists' satisfaction/dissatisfaction, and hence for the competitiveness of tourist destinations, studies focusing on tourists' satisfaction with their gastronomic experience are virtually non‐existent. More importantly, researchers have not yet produced evidence to support a factor structure of gastronomy satisfaction. The purpose of this paper is, therefore, to investigate the presence of a single second‐order factor by developing and empirically validating a second‐order factor analysis model for measuring satisfaction of gastronomic tourists in Portugal. As theorized, satisfaction comprised distinct first‐order factors and a single second‐order factor. The results suggest that gastronomy satisfaction in a tourism setting is a multidimensional construct comprising three factors: ‘gastronomy’, ‘price and quality’ and ‘atmosphere’. Among these three first‐order factors, ‘gastronomy’ was the most important determinant of tourist satisfaction, followed by ‘price and quality’ and ‘atmosphere’.

generally show greater differences (Box and Ramseur, 1993). Several methods have been used to estimate root Image analysis has greatly simplified the measurement of root length (Rowse and Phillips, 1974;Richards et al., 1979; systems, allowing more detailed and accurate assessment of standard Zoon and Van Tienderen, 1990). The most widely emroot variables. However, maize (Zea mays L.) root morphology has primarily been studied in conventional hybrids. We tested the hypoth-ployed methods are based on the line intersect principle, esis that genotypes carrying the leafy trait (taller plants with more which was first devised by Newman (1966) and later leaves and greater leaf area development) would have root morpholomodified (Marsh, 1971; Tennant, 1975). Because this gies differing from those of conventional maize hybrids. A 3 ϫ 3 method relies on visual counting of grid line-root interfactorial experiment was arranged in a randomized complete block cepts, it can be time consuming and prone to inaccuracy, design with three blocks, three fertilization levels (0, 127.5, and 255 especially when measuring samples with a large proporkg N ha Ϫ1 as NH 4 NO 3 ), and three maize genotypes [leafy reduced tion of fine roots (Smit et al., 1994). However, the line stature (LRS), leafy normal stature (LNS), and a conventional comintercept method improved root measurement and, in mercial hybrid Pioneer 3905 (P3905)]. The genotypes were selected particular, reduced the time required for analysis comfor their contrasting canopy and root architectures. Plants were grown pared with simpler, manual methods. For example, the in 63-L plastic containers, and the roots were measured at the silking stage (80 d from emergence) by scanner-based image analysis. In

Measurement of relatively small (<100 m total length, <6 g fresh wt.) root systems has been simplified by image analysis, but measuring larger root systems remains time‐consuming and inaccurate. Reliability of root estimation can be improved through identification of effective sampling methods. We devised a system for the collection of homogeneous root subsamples by air‐stirring in water. We optimized the subsampling technique and used a scanner‐based image analysis system to measure total root length, mean root diameter, and root surface area of three maize (Zea mays L.) genotypes with contrasting root morphologies: leafy reduced stature (LRS), leafy normal stature (LNS), and Pioneer 3905 (P3905), a commercial hybrid. Root length was determined for 957 subsamples. Confidence intervals were generated by software using the bootstrap resampling approach for optimizing sample size. Confidence intervals for mean estimates of each sample size were defined by ordering the evaluation function values from the smallest to the largest in a set of 5000 iterations. The lower and upper bounds of confidence intervals were also calculated using the standard procedure. This system allowed collection of homogeneous subsamples. Calculations showed that ∼10% of total root volume should be analyzed for estimation of the entire root system to be accurate within 10%. Although unreplicated, these data suggest that maize genotypes with the leafy trait have greater root lengths (1.75 km for LRS, 2.37 km for LNS, and 0.49 km for conventional commercial hybrid P3905) and a greater proportion of fine roots than the nonleafy type.

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environment, corn yield response to N amendments is poorly correlated with soil mineral N at preplant or Nitrogen amendment based on soil mineral N content before plantpresidedress (Ma and Dwyer, 1999). Postemergence aping is unreliable in humid regions. A field experiment was conducted for 3 yr to (i) determine the appropriate rates and timing of N applica-Costa, Univ. of Paso Fundo, Paso Fundo, RS, 99001-970, Brazil. Re-