摘要:

AbstractA field experiment was conducted to study growth characteristics of contrasting varieties ofLolium perenne(early heading:Gremie; late headingVigor) in different growth/regrowth periods during 1984 and 1985. A growth function was fitted to data of weekly measurements of dry matter production (DM) and leaf area index (L) to derive the following parameters according to quantitative analysis of plant growth: crop growth rate (C), relative growth rate (R), leaf area ratio (LAR) and leaf weight ratio (LWR). Furthermore phenological development of the swards was recorded.The chief differences in the growth potential of the varieties were found in primary growth on the one hand and in both investigated first regrowth periods on the other hand. In second and third regrowth periods no distinct differences were found either in DM nor in L regarding variety effects. In primary growth the early heading variety gained an advantage in DM, which was enhanced with prolonging growth period until the middle of June combined with a rapid reproductive development of the sward. Growth potential in the first regrowth period was determinated by the time of cutting in primary growth according to the development stage of the swards at cutting time. It was evident that highest values of DM and C were corresponding with a high amount of undamaged reproductive tillers in the sward. DM of vegetative summer regrowths were comparable, while in late summer/autumn under worsening environmental conditions a reduction in DM was observed. In opposite to that L developed rather similar in the investigated regrowth periods. According to this force of expression of L is discussed in relation to DM and phenological development of the swards.

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00847.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe concept of operational research in practical agriculture is introduced. Three aims of this approach are discussed and illustrated with actual examples in ley‐dairy farming‐to help understand and manage dynamic systems, such as growth‐to explain interactions and make predictions for current management measures, such as harvest time.‐to find alternative input combinations by sensitivity analyses.Prediction of ley growth and change in nutritional value illustrates the first point. It is shown that prediction of growth requires real time weather data but not necessarily weather forecasts. Alternatively, these can be substituted for data on normal weather conditions and some more extrem conditions of known probability.The second point is illustrated by analysing the main interactions that result in the margin above feed costs in the ley‐ruminant system. It is claimed that if the model satisfies an observed farm situation, as in this case, the explanation of the interactions is valid.The third point ‐ sensitivity analyses ‐ is illustrated by the higher margin over feed costs that is predicted in forage‐based feeding plans with 12‐15 kg DM forage, as compared to conventional feeding plans with 8 kg DM forage.The Discussion centres on (1) deterministic and stochastic models, (2) scale and experimental replication, and (3) statistical problems in parameter estimates and model validation:(1) When very dynamic systems are encountered, deterministic models may be difficult to validate. It is then far better to develop less precise stochastic models than to abolish the idea of model development. Such models would still predict risks and uncertainties.(2) With large systems such as production chains, experimental replicates often become too costly. A validated systems model then provides the possibility to explain unreplicated observations and state their generality.(3) Parameter estimates in mechanistic models require in many cases statistical developments because of problems encountered with non‐linear models where parameters may not be normally distributed.Requirements on model validation may differ when the models are used for long‐term or short‐term planning. In the second case, the model may be repeatedly calibrated to a current situation, and validation then includes the entir

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00848.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractIn a pot experiment two varieties of Jerusalem artichoke (Helianths tuberosusL., cv.Topiankaand cv.Violet de Rennes) were exposed to different supplies of N, P and K. Nitrogen supply increased tuber yield more than the productivity of aerial parts.Violet de Rennesresponded better to N thanTopianka.Nutrient regimes without P or K addition but including N to some extent depressed the yields of tubers only (by 8–23 %). Carbohydrate concentrations (78–81 % of d.m.) and molecular fructan distributions were neither influenced by fertilizer regimes nor by mineral concentrations in the tubers.Genotypic differences were significant for yield, for concentrations of N, P, Ca, S and Cu, and for fructan concentration in the tubers. At harvest time the fructose/glucose ratio in tubers ofViolet de Renneswas about 10 % higher than inTopiankaand remained on a higher level during storage.Harvest time had the greatest influence on carbohydrate composition. Depolymerization of fructan proceeded at a high rate in November and slowed down during subsequent storage, accompanied by a decline in polydispersity. Simultaneously osmolanty increased, resulting in a freezing point depression of<0.5

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00849.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractThe effects of supraoptimal root‐zone temperature (30 °C) on growth and development of roots were investigated in water and soil culture with cuttings of two potato clones DTO‐2 (heat tolerant) and LT‐1 (heat sensitive) at different plant ages, with different compositions of the nutrient solution, and different light intensities. It is suggested that the negative relation between cutting age and heat susceptibility observed in our experiments, is a reflection of the decreasing shoot/root dry weight ratio rather than of age. Heat damage of root systems increased with the concentration of the nutrient solution, nitrate being the main factor responsible. The influence of light intensity on temperature mediated restriction of root growth was relatively small. However the roots of plants grown under low light intensity (60 W m−2PAR) appeared to be less stressed by supraoptimal temperature, i.e. roots appeared brighter, thinner and more ramified than plants growing at high light intensity (19

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00850.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractA decrease in net photosynthesis (Pn) in leaves of main shoot with age (7‐28 days after opening) at two stages of peanut (Arachis hypogaeaL. var.M‐13) reproductive growth (70 and 90 DAS) is reported. Pnrate decreased with advance in age of leaves, the decline was rapid during peak period of pod filling (90 DAS). Foliar application with aliphatic alcohols, maintained the chlorophyll content and enhanced PEP carboxylase activity. The present studies suggest that aliphatic alcohols enhance functional capabilities of leaf for a larger duration and hence maintain the supply of photoassimilates to the developing kernels of peanut leading to increased yi

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00851.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractPlants exhibited differential response for ratoon growth and development under different temperature regimes before and after main crop harvest. Low temperature (23°/20 °C) before cutting induced ratooning whereas similar temperature after cutting delayed and reduced ratoon tillering. Ratoon grain yield and its attributes were significantly affected under various temperature regimes. Ratoon grain yield under low temperature regime before cutting did not differ from that of the control. Ratoon growth duration was maximum under low temperature regime after cutting. High temperature (37°/27 °C) after main crop cutting resulted in high spikelet sterility in the ratoon c

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00852.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

AbstractCytoplasmic effects on the photosynthesis was investigated in experimentally producedBrassica carinatasof reciprocal cytoplasmic origin. These are obtained by hybridizingB. nigraxB. oleraceavar.italica(B. carinata226) andB. oleraceaxB. nigra(B. carinata241). NaturalB. carinataand the two parents viz.B. nigraandB. oleraceavar.italicawere also included in this study. It was observed that the rate of photosynthesis inB. carinata226 with nigra cytoplasm, and naturalB. carinatawas higher than that ofB. carinata241 with oleracea cytoplasm. This was substantiated by the diurnal values of photosynthesis among these cultivars. The result indicated that the cytoplasm does affect the rate of photosynthesis inB. carinataand high photosynthetic efficiency in naturalB. carinatawas due toB. nigramaternal parent.

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00853.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY

摘要:

Books Reviewed in this Article:Fritz, D., W. Stolz, F. Venter, J. Weichmann, und Ch. Wonneberger: Gemüsebau.Stewart, B. A. (Ed.): Advances in Soil Science.Stewart, B. A. (Ed.): Advances in Soil Science.Klapp/Opitz von Boberfeld: Taschenbuch der Gräser.Ware, G. W. (ed.): Reviews of Environmental Contamination and Toxicology.Ware, G. W. (ed.): Reviews of Environmental Contamination and Toxicology.Ware, G. W. (ed.): Reviews of Environmental Contamination and Toxicology.Ware, G. W. (ed.): Reviews of Environmental Contamination and Toxicology.Ware, G. W. (ed.): Reviews of Environmental Contamination and Toxicology.Klimek, S.: Flachsanbau in Polen.Kaltofen, H. (Hrsg.): Züchtung und Anbau von Wiesenschweidel.Linskens, H. F. and J. F. Jackson (Eds.): Gases in Plant and Microbial Cel

ISSN:0931-2250    

DOI:10.1111/j.1439-037X.1990.tb00854.x

出版商:Blackwell Publishing Ltd    

年代:1990

数据来源: WILEY