The impact of soil compaction on soil aeration and fine root density of Quercus palustris

The soil around Quercus palustris trees, 30 cm (11.8 in) average diameter breast height (DBH) were treated by compaction (C) or C plus clay slurry (CS) treatments in November 1994 and repeated in May 1996. Soil oxygen diffusion rate (ODR), fine root density (FRD), DBH, twig growth, leaf area and dieback were monitored for 4 years beginning in 1996. Both compaction treatments significantly reduced ODR at 15 cm. Early each season, ODR was below the 0.20 g/cm²/min threshold level reported to inhibit root growth in several species [Stolzy, L.H., Letey, J., 1964. Correlation of plant response to soil oxygen diffusion rates. Hilgardia 35, 567–576] for all treatments and depths. In summer each year, ODR was adequate in the shallow soils of all treatments, though often still significantly lower in compacted soils. At 30 cm, there were no consistent differences in ODR between compacted and uncompacted soil. Significant differences in FRD due to compaction treatments were inconsistent and limited to the upper 9 cm of soil in years 2 and 3. Reduced FRD in compacted soils may be a response to the reduced ODR in spring. There were no differences in DBH, twig growth, leaf area or dieback rating. Given the minimal difference in root growth, the lack of differences in top growth are understandable. This controlled study, and others preceding it, have failed to clearly show the underlying causes of tree decline and death commonly associated with soil compaction and addition of fill soil in real landscapes.     

A comparative study of young ‘Thompson Seedless’ grapevines (Vitis vinifera L.) under drip and furrow irrigation. II. Growth, water use efficiency and nitrogen partitioning

The response of 3-year-old grapevines (Vitis vinifera L. cultivar ‘Thompson Seedless’) to furrow and drip irrigation was quantified in terms of water status, growth, and water use efficiency (WUE). Drip irrigation was applied daily according to best estimates of vineyard evapotranspiration while furrow irrigations were applied when 50% of the plant available soilwater content had been depleted. Drip and furrow irrigated vines showed similar water status (midday leaf water potential, Ψ₁) and shoot growth patterns throughout the season. Dry weight partitioning was not significantly different between treatments but root mass was somewhat larger for the furrow than drip irrigated vines. Nitrogen concentrations of the fruit and roots were significantly (P < 0.05) less for the drip irrigated vines when compared with the furrow treatment. Similar WUE (kg water kg⁻¹ fresh fruit wt.) were obtained for both treatments indicating that furrow irrigation was as efficient as drip irrigation under the conditions of this study. The data indicate that drip irrigation may increase the potential for control of vine growth by making vines more dependent on irrigation and N fertilization than furrow irrigation.     

Effects of N–P–K deficiency and temperature regime on the growth and development of Lilium longiflorum ‘Nellie White’ during bulb production under phytotron conditions

One-year-old scale bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown under a combination of six constant day/night temperature regimes and five N–P–K nutrient treatments under short days for 107 d (growing period 1 or GP-1) to compare the effects on growth and development and bulb production. Results during GP-1 were as follows: failure of bulblets to produce a shoot (“no-shows”) was found at high temperatures (30/26 and 26/22 °C) and not influenced by the nutrient treatments. Flower bud abortion was observed in the minus-N, minus-P, and minus-N–P–K treatments at high temperatures (30/26 or 26/22 °C), but not observed at any temperatures in the complete and minus-K treatments. The loss of bulb fresh weight in minus-N treated bulblets was less than in the other treatments resulting in less root and shoot growth in the minus-N treatment. At the intermediate temperatures where growth was highest, omission of N, P, K, or all three resulted in losses in stem bulb fresh weight, stem plus leaf fresh weight, number of flowers, and stem root fresh weight. Omission of N, P, or all three nutrients resulted in lowest basal root fresh weight. Bulb N and K concentrations were lowest in plants grown with complete nutrient solution at the two coldest temperature regimes (14/10 and 10/6 °C). Bulb P concentration was lowest at the three coldest (18/14, 14/10 and 10/6 °C) and the warmest (30/26 °C) temperature regimes. Stem length was shorter when P was omitted. Omission of any of the three nutrients resulted in lower concentrations of the other nutrients. The one exception was where low K did not affect N concentration. In the second phase of the experiment, plants grown at 18/14 °C and irrigated with the complete nutrient solution for 107 d (GP-1) were continued at this day/night temperature regime and five N–P–K nutrient treatments for another 89 d under long days (growing period 2 or GP-2). Results during GP-2 were as follows. Basal bulb yield was not impacted by omission of N, P, or K, or all three. Of all growth measurements, only stem plus leaf fresh weight was lower and only when all three nutrients (minus-N–P–K) were omitted. At the end of GP-2, basal bulb concentrations of N and P did not differ from the concentrations in bulbs at the beginning of GP-1; however, K concentration was lower at the end of GP-2. Omission of N or P further resulted in lower bulb K concentration, suggesting that a moderate supply of N, P, and K be applied during GP-2 since an additional year of bulb production is needed to produce forcing-sized bulbs.     

Growth and development of Lilium longiflorum ‘Nellie White’ during bulb production under controlled environments : II. Effects of shifting day/night temperature regimes on scale bulblets

One-year old scale bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown for 107 days during growth period 1 (GP-1) in six growth chambers under constant day/night temperature regimes of 30/26, 26/22, 22/18, 18/14, 14/10 and 10/6 °C. Subsequently, half of the plants in each temperature regime were transferred to 18/14 °C and the other half continued at the six constant temperature regimes. Both groups of plants were grown for an additional 89 days in growth period 2 (GP-2). Continuous temperatures of 26/22, 26/22–22/18 and 26/22–18/14 °C produced the greatest increase in basal bulb fresh weight (the main planted bulb), basal bulb circumference and stem bulb fresh weight, respectively. However, shifting these optimal temperatures to 18/14 °C during GP-2 resulted in a lower increase in basal bulb fresh weight and circumference. The optimum range for stem bulb production was expanded to 30/26–14/10 °C by shifting to 18/14 °C. The greatest increase for basal root growth occurred at 14/10–10/6 °C and for stem root growth at 14/10 °C. The temperature shift did not affect either root type. Maximum increase for stem length was at 26/22 and 22/18 °C and for stem plus leaf weight at 14/10 °C under constant temperature regimes. Transferring the plants from 10/6 to 18/14 °C resulted in the greatest increase in stem length and from 10/6 and 14/10 to 18/14 °C in the greatest increase in stem plus leaf weight. The greatest increase in the number of leaves occurred at 26/22 and 10/6 °C, but this growth parameter was unaffected by shifting to 18/14 °C, indicating that leaf number was determined in GP-1. Bulbils developed only when bulbs at high GP-1 temperature regimes (30/26 and 26/22 °C) were transferred to 18/14 °C during GP-2. Lower temperatures tended to favor an increase in flower bud production under continuous temperature regimes, while shifting to 18/14 °C increased flower bud production after initially high and low temperatures. Meristem abortion was greatest at 30/26 °C followed by 26/22 °C, but was not affected by temperature shifts in GP- 2. Thus, it is concluded that the abortion was induced or initiated during GP-1.     

Growth and development of Lilium longiflorum ‘Nellie White’ during bulb production under controlled environments : I. Effects of constant,variable and greenhouse day/night temperature regimes on scale and stem bulblets

One-year-old scale and stem bulblets of Lilium longiflorum Thunb. ‘Nellie White’ (Easter lily) were grown under constant and variable growth chamber conditions and greenhouse conditions to compare growth and development and bulb production. Eight temperatures regimes were established using the following: six growth chambers set to provide day/night temperature regimes of 30/26, 26/22, 22/18, 18/14, 14/10 and 10/6 °C; a seventh growth chamber (VAR) programmed to begin at 22/18 °C, then decline in three 4–5 week steps to 10/6 °C, and subsequently increase in three 4–5 week steps to 22/18 °C to simulate seasonal field temperatures in the coastal bulb production area of northern California and southern Oregon; and a double layer polyethylene greenhouse (GH) set to begin cooling at 22 °C and heating at 18 °C. Ten percent of the scale bulblets and 35% of the stem bulblets failed to develop shoots (“no-shows”). “No-shows” increased with increasing temperature with a significant number starting at 18/14 °C. The moderately high GH temperature also induced “no-shows”. Maximum basal bulb (the main planted bulb) weight occurred at 26/22 °C for both bulblet types. Scale bulblets not only produced heavier basal bulbs with a larger circumference than stem bulblets, but also produced heavier stem bulbs. Stem bulb formation and production was maximized in the range of 18/14–26/22 °C and in the GH for scale bulblets. Stem bulb production from stem bulblets did not differ from zero. Scale bulblets produced more basal and stem roots than the stem bulblets at the end of the early growth period, but there was no significant difference at the end of the study. Root fresh weight was greatest in the range of 14/10–18/14 °C and declined at higher or lower temperatures. The VAR and GH treatments had similar root weights to those at 18/14 °C. Shoot length was maximized at 22/18 °C for stem bulblets and in the GH and at 22/18 °C for scale bulblets. Stem plus leaf (shoot) fresh weight was not statistically different between bulblet types with the exception of an increased weight for stem bulblets grown at 22/18 °C. Scale bulblets in the GH had greater stem plus leaf weights than scale bulblets in the other temperature regimes. Shoot leaf number was highest in stem bulblets at 22/18 °C and in the GH. In these two temperature treatments, more leaves were produced by stem bulblets than scale bulblets. In all other treatments, there was no significant difference in leaf number. Bulblet type had no effect on number of flowers produced. Flower number was maximum in the range 10/6–22/18 °C, decreased at 26/22 °C and in the GH, and was absent at 30/26 °C. For bulb production, reduced flowering is desired since flowers are generally removed during the outdoor bulb production period. Meristem abortion, which also causes a desirable reduction in flowers, was greater in scale bulblets. It occurred at 26/22 °C and was greater at 30/26 °C. Scale bulbs produced the largest main bulbs, with a maximum yield at 26/22 °C.     

Effects of CO2, temperature and their interaction on the growth, development and yield of cauliflower (Brassica oleracea L. botrytis)

Stands of summer cauliflower were grown within polyethylene-covered tunnels along which a temperature gradient was imposed. Two tunnels were maintained at either normal or elevated CO₂ concentrations. At the last harvest (88 days from transplanting) no interaction between CO₂ and temperature on total biomass was detected. The total dry weight of plants grown at 531 μmol mol⁻¹ CO₂ was 34% greater than those grown at 328 μmol mol⁻¹ CO₂, whereas a 1 °C rise reduced dry weight by 6%. From serial harvests the radiation conversion coefficient was 2.01 g MJ⁻¹ and 1.42 g MJ⁻¹ at 531 μmol mol⁻¹ CO₂and 328 μmol mol⁻¹ CO₂, respectively, but was not greatly affected by differences in temperature. No effect of either CO₂ or temperature on the canopy light extinction coefficient was detected. The rate of progress towards curd initiation increased to a maximum at 15.5 °C, and declined thereafter. Provided the effect of temperature was accounted for, CO₂ enrichment did not affect the time of curd initiation. From serial harvests after curd initiation, the logarithm of curd weight or diameter were negative linear functions of mean temperature from initiation. Increases in curd weight and diameter at 531 compared with 328 μmol mol⁻¹ CO₂ were greater at warmer temperatures (27% at 13 °C compared with 47% at 15 °C, 57 days after initiation). Effects of CO₂ on curd diameter were less than those on curd dry weight because the curd dry matter content was greater at 531 compared with 328 μmol mol⁻¹ CO₂. Thus, the effects of elevated CO₂ concentrations on fresh weight based yield parameters of cauliflower were less than the increase in total dry matter production.     

Growth, survival, and root system morphology of deeply planted Corylus colurna 7 years after transplanting and the effects of root collar excavation

Urban trees are frequently planted with their root collars and structural roots buried well below soil grade, either because of planting practices, nursery production practices, or both. These deeply planted structural roots can impair tree establishment and are thought to reduce tree growth, lifespan, and stability, although research has provided few and contradictory results on these questions to date. This study examines container-grown (55 L) Turkish hazel trees (Corylus colurna L.), planted either at grade, 15 cm below grade, or 30 cm below grade into a well-drained silt loam soil, over nearly 8 years. Five years after planting, in 2004, remediation treatments (root collar excavations) were performed on two replicates of each below-ground treatment. Subsequently, all trees were subjected to flooding stress by being irrigated to soil saturation for approximately 6 weeks. In 2006, flooding stress was repeated. Trees root systems were partially excavated in 2007, and root architecture was characterized. Deep planting did not affect trunk diameter growth over 8 years. Survival was 100% for the first 5 years; however, one 30 cm below grade tree died after flooding in 2004 and another died after the 2006 flooding. Photosynthesis was monitored during the 2004 flooding and all trees experienced decline in photosynthetic rates. There was an apparent slight delay in the decline for trees with excavated root collars and those planted at grade. Girdling roots reduced trunk taper and occurred primarily on unremediated trees planted 30 cm below grade.

Selected individual roots were excavated and followed from the root ball and were observed to gradually rise to the upper soil regions. Analysis of roots emerging from excavation trench faces indicated that vertical root distribution at approximately 1.25 m from the tree trunks was the same regardless of planting depth. Longterm consequences of planting below grade are discussed.     

Growth and nutrient partitioning of containerized Cercis siliquastrum L. under two fertilizer regimes

Lebanon's native flora is threatened by loss of natural habitat to rural and urban development and the increased demand of plant materials for landscaping. Despite Lebanon's floristic richness, most taxa used for landscaping are non-native. This study was done to determine if Cercis siliquastrum (L.) is amenable to container production. Therefore, six open pollinated seeds sources native to Lebanon were grown under two fertilizer rates to study growth, N, P, K uptake efficiency, and partitioning. Two-year-old seedlings were planted in 11 L containers in a 3:1 pine bark:compost substrate. Seedlings within each seed source or mother tree were grown at either 25 or 100 mg N L⁻¹ from 21N–3.1P–5.9K water-soluble fertilizer. Seedlings of all sources grown under 25 mg N L⁻¹ had greater dry weight than those grown at 100 mg. Nutrient loading occurred in plants under the high fertilizer rate, although total plant N, P, and K content were not affected by fertilizer rate. There were significant differences in mineral nutrient uptake and nutrient use efficiencies among the seed sources. The results show that C. siliquastrum is amenable to container production. The great variation in growth rate and nutrient use efficiency among the limited number of seed sources studied suggest that significant improvement can be made through mother tree selection and/or clonal propagation of superior individual plants within a source.     

桂花在不同灌木环境下生长的差异

对生长在娄底市金叶女贞和杜鹃不同灌木环境下的桂花进行树高、地径、冠幅等生长情况调查.结果表明:杜鹃中的桂花长势明显强于女贞中的桂花.     

In vitro micropropagation of the ornamental prickly pear cactus Opuntia lanigera Salm–Dyck and effects of sprayed GA3 after transplantation to ex vitro conditions

We established the conditions to micropropagate the ornamental prickly pear cactus Opuntia lanigera Salm–Dyck through axillary shoot development from isolated areoles. For the shoot proliferation stage different explant orientation (vertical and horizontal), type of cytokinin (BA, DAP and K), and concentrations (0, 1.25, 2,5, 5.0 and 7.5 mg/L) were evaluated. Media [Murashige, T., Skoog, F., 1962. A revised medium for rapid growth and bioassays with tobacco cultures. Phys. Plant. 15, 473–497: 50 and 100%], and carbohydrate concentration (0.25, 0.5, 0.75 and 1.0%) were studied to optimize individual shoot growth and elongation. Following micropropagation and plantlet acclimatization, the effects of GA₃ on plant growth were determined by spraying a series of increasing concentrations (0, 150, 300 and 450 ppm). A reliable and efficient protocol of micropropagation was established for this particular plant species. The greatest propagation ratio (shoot proliferation) was obtained when explants were cultured in vertical orientation (4.975 shoots per explant) as compared to horizontal position (3.692 shoots per explant). The addition of BA to the media resulted in increased shoot number per explant (8) in comparison to K and DA, which produced only 2 shoots in average. However, after 42 days of culture, significantly higher shoot length was obtained with DAP (14 mm) compared to K and BA (4 mm). After the shoot proliferation stage, an elongation subculture was performed prior rooting in which shoot growth was enhanced when crowns of shoots were cultured in 50% of basal salt formulation of Murashige and Skoog (1962) and low sucrose concentration (2.5 and 5%). Exogenous application of GA₃ after plantlet acclimatization on glasshouse conditions increased spine-hair (developed from areoles in young plants) length as part of short-term effects. However, significantly higher values were obtained in plantlets treated with 300 ppm of GA₃ when compared with the rest of the treatments. At the end of the study, the most important long-term effect produced by GA₃ was the suppression of total shoot growth. The micropropagation protocol described here and the conditions to grow the plants through fertigation plus the application of GA₃ that induced changes in the phenotype may be used in commercial exploitations to regenerate 12,500 plantelts in average after 12 months of culture and produce healthy plants with better ornamental characteristics and higher commercial value.     

Isolation of arbuscular mycorrhizal fungi and Azotobacter chroococcum from local litchi orchards and evaluation of their activity in the air-layers system

Soil samples were collected from rhizosphere of litchi-growing areas of North-Western Himalayan Region (NWHR) of India, for finding qualitative and quantitative differences in arbuscular mycorrhizal (AM) fungi and Azotobacter chroococcum. These samples were taken from plants being grown in different cultivation types namely, weed control with weedicides or tillage; orchard floor either clear or with cover crops; intercropping with cereals and legumes. Qualitative and quantitative differences were noticed with different cultivation types and a marked reduction in the AM fungi was observed in orchards where chemicals were used for weed control and intensive farming system was used on the orchard floor. AM fungi were generally abundant in the soils with range pH 5.5–6.6. Among different AM fungi retrieved from the soils, Glomus spp. was most dominant. Fifteen AM fungal species were isolated, identified and characterized and along with their ability to colonize the roots. In the soil samples, a marked variation in viable bacterial count of A. chroococcum was also noticed due to varied physico-chemical characteristics of the orchard soils. The changes in AM fungal species composition can be attributed to changes in soil chemical properties resulting from cultural practices such as ploughing, application of chemical fertilizers and weedicides. An experiment was also conducted to study the comparative efficacy of four dominant and frequently occurring indigenous AM species namely, Glomus fasciculatum (Thaxter sensu Gerdemann), G. magnicaulis (Hall), G. mosseae (Nicol. & Gerd.), Gigaspora heterogamma (Nicol. & Gerd.) and two A. chroococcum strains viz., AZ₁ and AZ₂ singly and in dual combination to evaluate their effect in air-layers system. Dual inoculation of G. fasciculatum and AZ₁ increased total root length of air-layered shoots by 81.39% over uninoculated control. These studies indicated that indigenously isolated AM fungal species and A. chroococcum strains can be used for air-layering for better adaptation under specific agro-climatic and ecological zone conditions.     

Influence of potential growth factors on the production of proembryogenic masses of Cyclamen persicum Mill. in bioreactors

Propagation in liquid culture, especially bioreactors, is one possible way to produce clonal propagules of Cyclamen persicum Mill. at a low cost. The current propagation method for C. persicum is from expensive hybrid seeds. This paper presents models of the potential effects of oxygen concentration, daily mean temperature, the difference between day and night temperature (DIF), and daily light integral on the development of proembryogenic masses of C. persicum Mill. in bioreactors. Each of the four growth factors was observed at three levels; oxygen concentration (50, 100 and 150% of fully oxygen saturated medium without cells), daily mean temperature (15, 20 and 25 °C), DIF (+10, 0 and −10) and daily light integral (0, 1.3 and 2.6 mol m⁻² day⁻¹). Two response variables, biomass growth and cell viability, were measured at day 0, 7, 14, 21 and 28 after start-up. The optimal values for biomass growth were 150% oxygen, 25 °C, 1.11 mol m⁻² day⁻¹ and DIF + 10. There was a stable positive linear effect from temperature. Oxygen showed a similar, but less stable effect. DIF gave maximum effect at the outer levels, and its optimum was the upper level +10. The optimal values for light were between 1.03 and 1.19 mol m⁻² day⁻¹. The optimal time for cell viability in the bioreactors was 10–11 days. Temperature and daily light integral had stable optima of 20.8 °C and 1.10 mol m⁻² day⁻¹. For oxygen the optimum was more unstable, but in most cases it was below 100%. There was no significant effect of DIF on cell viability.     

The influence of the topographic position within highlands of Western Rwanda on the interactions between banana (Musa spp. AAA-EA), parasitic nematodes and soil factors

Soil properties vary according to the topography. They affect water uptake and root exploration in the soil. Consequently, they may also influence the spread of plant–parasitic nematodes. This study reports on the effect of toposequence-related variations in soil on banana yields, foliar nutrient status, and nematode impact. Twenty banana plots were visited within 6 hills/valleys at each of the three toposequence positions: valley bottom, mid-slope and crest. Important variability in plant growth, nutrition and soil properties was observed within the toposequence. Significantly better plant growth (height and girth) was observed in the valley bottoms, where banana bunch weight was 1.7–3.4 kg higher (although not significant) than at upper toposequence positions. Best plant growth was observed in valley bottoms in contrast to the highest N and K foliar deficiencies in this position. Plants in the valley bottoms had higher foliar Ca and Mg, and K compared to those in the crest. Plants in the mid-slope had greater percentage of dead roots (19.1%), compared to the plants in the valley bottoms (12.3%) and the crest (14.2%). Soils in the valley bottoms were deeper, sandier, with lower organic matter, lower N, and K compared to the soils at higher toposequence. Nematodes likely play a key role in banana root damage, however, their effect appear to be in relation to various soil factors at each position. The abundance of Pratylenchus goodeyi had generally limited impact on banana yields in fields having less than 5% slope (crest and valley bottom) where soil conditions were more optimal for root growth. However, in the presence of increased run-off on steeper middle slopes, root death was increased even under moderate pressure from P. goodeyi.