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21.
Fruit characteristics of the disease-resistant bluggoe-type (ABB) cooking bananas (Musa × paradisiaca L.) ‘Saba’ and ‘Pelipita’ were compared with those of the susceptible ‘Currare’ (‘Horn’). Yields of ‘Saba’ and ‘Pelipita’ were similar to those of ‘Currare’; however, ‘Saba’ and ‘Pelipita’ yielded fewer hands with a greater number of small fruit when compared with ‘Currare’. Shoot-tip cultures of both clones were readily initiated on a modified Murashige and Skoog (MS) basal medium supplemented with N6-benzyladenine (BA) in combination with indole-3-acetic acid (IAA). Propagation cultures were initiated by splitting shoot tips along their longitudinal axis and re-culturing the individual pieces to basal medium supplemented with 5 mg l?1 BA. Transfer of axillary shoots to hormone-free medium resulted in rapid and extensive root formation. Plantlet survival after transfer to methyl bromide-treated soil exceeded 90%. Establishment in the field was achieved following procedures normally used for vegetative propagation of this crop. Trial plantings of in vitro propagated ‘Saba’ and ‘Pelipita’ were established in various provinces of Costa Rica for grower evaluation and for future comparison of growth and reproductive development with plants of these and other cultivars propagated from corms.  相似文献   
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The amount of photosynthetic radiation intercepted by a crop is a function of the incident solar radiation on the plants, the leaf area index (L AI), and the light extinction coefficient (k). We quantified L AI and k in stands of black wattle (Acacia mearnsii De Wild.) over a 7-year growth cycle at two locations in the state of Rio Grande do Sul, Brazil. Our study was conducted in commercial stands in agroecological regions with high densities of black wattle plantations. L AI was calculated as the ratio between the leaf area of a tree and its planting space, and k was derived from Beer’s law. L AI depends on the planting site and stand age. Between the two sites, the L AI was similar over time, the amount of variation differed. Values of k depended only on stand age, with the highest average observed for stands up to 5 years old. The trend of k during the plantation cycle was inversely proportional to L AI and was correlated with L AI, leaf area, leaf dry mass, canopy volume, height, branches dry mass, total dry mass, and crown diameter.  相似文献   
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Major disturbances that remove vegetation cover create conditions that differ greatly from those in adjacent forests. In volcanic areas, tephra deposition can be a major disturbance that eliminates vegetation cover and creates a barrier for plant establishment. The eruption of the Paricutín volcano, in Michoacán, México, from 1943 to 1952, created large tephra deposits adjacent to forest stands. Many of these deposits still lack native vegetation and understanding of the limiting factors for establishment of native tree species is necessary to restore these areas. Pinus pseudostrobus early growth in response to the amount of fertile growing medium on top of a variable-depth tephra layer was evaluated in a greenhouse experiment. Increasing amounts of fertile growing medium increased height of 28-week-old plants (no growing medium = 5.5 cm tall ±1.8 cm, 3 cm of growing medium = 21.2 ± 4.6 cm and 6 cm of growing medium 24.8 ± 4.4 cm). Other variables showed the same trend (diameter, number of fascicles, belowground biomass and aboveground biomass). Our results suggest that P. pseudostrobus establishment in tephra covered areas will depend on the accumulation of a fertile layer of more than 3 cm in thickness.  相似文献   
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Changes in soil chemical and microbiological parameters in small (185 m2) and medium (410 m2) gaps, created in mature silver fir (Abies alba Mill) stands (mean height 30 m) in the Calabrian Apennines (Southern Italy), were studied over 2 years. Medium gaps had high soil temperature and photosynthetically active radiation (PAR) transmittance and low soil moisture. Within small gaps we detected a greater amount of organic matter, with respect to under canopy cover sites and medium gaps. Moreover, a different trend of the organic matter between small and medium gaps was observed. In the medium gaps, with respect to under canopy cover sites and small gaps, we found a relatively low content of organic matter, associated to a lower amount of humic acid, which suggested that the organic substrate undergoes a mineralization rather than a humification process. An opposite trend was observed in small gaps, where the increase of organic matter content, associated to an increase of humic acid and microbial biomass, suggested a better humification process. Moreover, in small gaps the highest level of urease and the greatest fluorescein diacetate (FDA) hydrolysis were observed. The different trend of organic matter observed in small and medium gaps may be related to changes in the environmental conditions. PAR transmittance, significantly higher in medium gaps, contributed to increase soil temperature and decrease soil moisture, affecting soil microbial populations and organic matter trend. These results suggest that the creation of small gaps represents the silvicultural practice with minor environmental impact.  相似文献   
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PCR products obtained by selective amplification of transgenic DNA derived from food samples containing Roundup Ready soybean or Bt-176 maize have been analyzed by anion-exchange HPLC. Peptide nucleic acids (PNAs), oligonucleotide analogues known to bind to complementary single-stranded DNA with high affinity and specificity, have been used as specific probes in order to assess the identity of the peaks observed. Two different protocols were adopted in order to obtain single-stranded DNA: amplification with an excess of one primer or digestion of one DNA strand. The single-stranded DNA was mixed with the PNA probe, and the presence of a specific sequence was revealed through detection of the corresponding PNA:DNA peak with significantly different retention time. Advantages and limits of this approach are discussed. The method was tested with reference materials and subsequently applied to commercial samples.  相似文献   
29.
Field-grown olive trees (Olea europaea L. cv. Leccino) were used over two growing seasons to determine the effect of deficit irrigation regimes on virgin olive oil (VOO) quality. Drip irrigation was managed to maintain a predawn leaf water potential (PLWP): (a) higher than -1.1 MPa (full irrigation: FI); (b) between -1.0 and -3.3 MPa (deficit irrigation: DI); (c) higher than -4.2 MPa (severe deficit irrigation: SI). The fruit yield and oil yield of DI trees were over 90% of those of FI treatments in both years, respectively, whereas yields of SI trees ranged from 61 to 76%. The irrigation regime had minor effects on the free acidity, peroxide value, and fatty acid composition of VOO. The concentrations of phenols and o-diphenols in VOO were negatively correlated with PLWP. The concentrations of the dialdehydic form of decarboxymethyl elenolic acid linked to (3,4-dihydroxyphenyl)ethanol (3,4-DHPEA-EDA), the isomer of the oleuropein aglycon (3,4-DHPEA-EA), and the dialdehydic form of decarboxymethyl elenolic acid linked to (p-hydroxyphenyl)ethanol (p-HPEA-EDA) were lower in FI than in SI treatments. The concentrations of lignans (+)-1-acetoxipinoresinol and (+)-1-pinoresinol were unaffected by the irrigation regime. The tree water status had a marked effect on the concentration of volatile compounds, such as the C(6)-saturated and unsaturated aldehydes, alcohols, and esters.  相似文献   
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Agroforestry Systems - Tropical agroforestry practices play a crucial role in mitigating global climate change by absorbing CO2 from the atmosphere through photosynthesis and storing carbon in...  相似文献   
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