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21.
Summary A major objective of plant breeding programmes in semi-arid conditions is the selection of more drought-tolerant plant material.
An irrigation system has been developed to assist in water use and drought tolerance screening studies of potato genotypes
in the confined space of a rain shelter. The line-source principle was used as a departure point for the design of an irrigation
boom, attached to the roof structure of a rain shelter. Five water regimes were achieved by using nozzles that differed in
discharge rate and three genotypes per rain shelter were evaluated simultaneously.
Crop production functions could be established for the different genotypes. The system shares some disadvantages of the typical
line-source, such as the simultaneous irrigation of all plots and water treatments are not randomised. The main advantage
above traditional plot systems, which would use drip or micro irrigation under rain shelters, is the ease of management. 相似文献
22.
Summary Observations were made on dormancy and sprout growth of nine potato cultivars stored at 3–4°C, 7–8°C and 11–12°C, respectively.
Tubers of the cultivar Vanderplank had a very long dormant period (232 days at 3–4°C) and showed little sprout growth at 180
days. The cultivar Koos Smit had a very short dormant period (92 days at 3–4°C) and developed considerable sprout growth at
the higher temperatures. The reaction of tubers of Up-to-date and BP1 were approximately the same, and intermediate between those of Vanderplank and Koos Smit. 相似文献
23.
Anne Hoffmann Sabine Milde Christine Desel Anja Hümpel Hartmut Kaiser Enno Hammes Mirva Piippo Arto Soitamo Eva‐Mari Aro Jóska Gerendás Burkhard Sattelmacher Ulf‐Peter Hansen 《植物养料与土壤学杂志》2007,170(1):87-97
Ammonium (NH ) nutrition causes retardation of growth in many plant species. In Arabidopsis grown with NH as the sole N source, growth retardation occurs already at early stages before photosynthesis has come to its full power. In order to describe the peculiarities of these retarded plants, they were compared with nitrate (NO )‐grown plants of the same age of 15 d. Photosynthetic activity as measured by CO2 uptake per unit chlorophyll is half as high in NH ‐grown seedlings as in NO ‐grown ones. This finding is confirmed by the analysis of chlorophyll fluorescence. Chloroplasts of NO ‐grown, but not of NH ‐grown, seedlings show starch deposits after 5 h of illumination with 40 μmol m–2 s–1. Gene‐expression analysis based on cDNA microarray and on Northern blots provide a clue about the biochemical background. After the first 2 weeks of growth, it seems that NO ‐grown seedlings subsist mainly on normal photosynthesis, whereas NH ‐grown seedlings still use lipids from the seeds stored in oleosomes. Corresponding to this observation, the mRNAs for enzymes of β‐oxidation are more strongly expressed in NH ‐grown seedlings. Different carbohydrate sources for sucrose synthesis are indicated by different gene expression. Higher gene expression of fructose bisphosphate aldolase (cytosolic isoform) in NO ‐grown seedlings indicates the dependence on photosynthesis, whereas a higher gene expression of PEP carboxykinase in NH ‐grown seedlings points to a prominent role of β‐oxidation of storage lipids still present. 相似文献
24.
Most of the sandy soils that are suitable for production of groundnut (Arachis hypogaea L.) in the tropic and subtropics are acidic. Whilst effects of pH in the root zone have been studied, the effects of pod-zone pH on groundnut productivity remain relatively unknown. To develop appropriate soil management practices for groundnut production on acid soils, it is essential to understand how low pH affects reproductive growth of groundnut. Consequently, a glasshouse experiment was conducted in which attached groundnut gynophores were cultured in solution at pH ranging from 3.0 to 7.0. Low pH delayed pod initiation, and resulted in almost no pod expansion at pH 3.0. Only 12% and 55% of the cultured gynophores developed into pods at pH 3.0 and 4.0, respectively, compared with 91–95% at pH ≥ 5.0. Pods produced at pH 3.0 contained no seeds and those produced at pH 4.0 had a hollow, dark colored area in the cotyledon. Normal seeds and embryos were formed at pH ≥ 5.0, and plumule development was faster at solution pH ≥ 5.0 than at pH 4.0. Pod and kernel dry mass were optimised (90% of maximum) at pH 5.62–6.69 and 5.65–6.78, respectively. Septate and non-septate pod hairs were formed at all solution pH regimes, but were denser and more persistent at the higher pH. Kernel calcium (Ca) concentration decreased with decreasing pH, and was highly correlated with solution pH. Thus, pod-zone pH has important effects on the reproductive growth of groundnut, emphasizing the importance of managing pod-zone pH. 相似文献
25.
Ene Tooming Enno Merivee Anne Must Ivar Sibul Ingrid Williams 《Pest management science》2014,70(6):959-966
26.
Indoxacarb is a new oxadiazine insecticide that has shown outstanding field insecticidal activity. The toxicity of a 145 g litre-1 indoxacarb SC formulation (Steward) was studied on the tarnished plant bug Lygus lineolaris and the big-eyed bug Geocoris punctipes. Both insect species responded very similarly to indoxacarb in topical, tarsal contact and plant feeding toxicity studies. The topical LD50 of the formulation was c 35 ng AI per insect for both species. Prolonged tarsal contact with dry indoxacarb residues did not result in mortality for either insect species. However, both species were susceptible to feeding through dried residues of indoxacarb after spraying on young cotton plants. Feeding on water-washed plants resulted in lower mortality than that observed with unwashed plants, and toxicity declined even more dramatically after a, detergent rinse, indicating that much of the indoxacarb probably resides on the cotton leaf surface or in the waxy cuticle. These results were corroborated by HPLC-mass spectrometry measurements of indoxacarb residues on the plants. Greater mortality for both species was observed in a higher relative humidity environment. Higher levels of accumulated indoxacarb and its active metabolite were detected in dead G punctipes than in L lineolaris after feeding on sprayed, unwashed plants. When female G punctipes ate indoxacarb-treated Heliothis zea eggs, there was significant toxicity. However, only c 15% of the females consumed indoxacarb-treated eggs, and the rest of the females showed a significant diminution of feeding in response to the insecticide. Cotton field studies have shown that indoxacarb treatments at labelled rates lead to a dramatic decline in L lineolaris, with negligible declines in beneficial populations. A major route of intoxication of L lineolaris in indoxacarb-treated cotton fields thus appears to be via oral, and not cuticular, uptake of residues from treated cotton plants. The mechanisms for selectivity/safety for G punctipes are currently under investigation and may be a combination of differential feeding behavior and diminution of feeding by females exposed to indoxacarb-treated eggs. 相似文献
27.
Coupled thermal and hydrological evolution of tropical Africa over the last deglaciation 总被引：2，自引：0，他引：2
Weijers JW Schefuss E Schouten S Sinninghe Damsté JS 《Science (New York, N.Y.)》2007,315(5819):1701-1704
We analyzed the distribution of branched tetraether membrane lipids derived from soil bacteria in a marine sediment record that was recovered close to the Congo River outflow, and the results enabled us to reconstruct large-scale continental temperature changes in tropical Africa that span the past 25,000 years. Tropical African temperatures gradually increased from approximately 21 degrees to 25 degrees C over the last deglaciation, which is a larger warming than estimated for the tropical Atlantic Ocean. A direct comparison with sea-surface temperature estimates from the same core revealed that the land-sea temperature difference was, through the thermal pressure gradient, an important control on central African precipitation patterns. 相似文献