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Digitale Medien

Temporal expression of effects of varying nitrogen supply on canopy growth, photosynthesis and fruit production for Actinidia deliciosa vines in the field (1993)

Buwalda, J. G. ; Meekings, J. S.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 89 (1993), S. 0

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ISSN: 1399-3054

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: The effects of varying nitrogen supply on canopy leaf area, response of leaf net photosynthesis (An) to quantum flux density (Q), and fruit yields of kiwifruit vines (Actinidia deliciosa var. deliciosa) were examined in a two-year field experiment. Vines were grown with 0, 250 or 750 kg N ha−1 year−1. The responses to nitrogen supply were compared with responses to shade, to examine the impact of reduced carbon assimilation on canopy leaf area and fruit yields. Nitrogen supply did not affect significantly any of the measured variables during the first season of the experiment. In the second season, canopy leaf area was reduced significantly where nitrogen supply was limited. The quantum efficiency of photosynthesis (φq) increased from 0. 03 mol CO2 mol−1 Q soon after leaf emergence to more than 0. 05 mol CO2 mol−1 Q during the middle of the growing season. The quantum saturated rate of An (Asat) also increased during the season, from 7–10 μmol CO2 m−2 s−1 soon after leaf emergence, to 15–20 (μmol CO2 m−2 s−1 during the middle of the growing season. φq and Asat increased significantly with nitrogen supply at all measurement times during the second season. For vines with high nitrogen, fruit yields in both seasons were similar, averaging 3. 05 kg m−2. Fruit yields in the second season were reduced significantly where nitrogen supply was limited, due to reduced fruit numbers. The relative effects of reduced leaf area and reduced leaf photosynthesis for carbon assimilation by nitrogen deficient vines were examined using a mathematical model of canopy photosynthesis for kiwifruit vines. Simulations of canopy photosynthesis indicated that effects on leaf area and on leaf photosynthesis were of similar importance in the overall effects of nitrogen deficiency on carbon assimilation. The effects of nitrogen supply on fruit numbers (i. e. flower development) preceded the measured effects on carbon assimilation, indicating that the nitrogen supply affected carbon partitioning to reserves in the first season.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1399-3054.1993.tb01785.x

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Digitale Medien

Seasonal changes in photosynthetic capacity of leaves of kiwifruit (Actinidia deliciosa) vines (1991)

Buwalda, J. G. ; Meekings, J. S. ; Smith, G. S.

Oxford, UK : Blackwell Publishing Ltd

Physiologia plantarum 83 (1991), S. 0

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ISSN: 1399-3054

Quelle: Blackwell Publishing Journal Backfiles 1879-2005

Thema: Biologie

Notizen: The seasonal trend of photosynthetic capacity of leaves of kiwifruit (Actinidia deliciosa var. deliciosa) vines growing in the field was examined, by measuring the response of net photosynthesis (A) to irradiance (PAR) at monthly intervals for leaves that emerged at different stages of the growing season. A climate controlled minicuvette system was used, to ensure constant environmental conditions, apart from the controlled changes in leaf irradiance. Responses of A to irradiance were described using asymptotic exponential curves, providing estimates of the radiation saturated rate of A (Asat), and the reponse of A to increasing incident PAR at low PAR levels (ϕi). The change in photosynthetic capacity with leaf age was similar for leaves emerging 1, 2, 3 or 4 months after bud burst. At 1 month after leaf emergence, when leaves were fully expanded, Asat was 9–11 μmol CO2 m−2 s−1. Maximum photosynthetic capacity was not attained until 3–5 months after leaf emergence, when Asat was 16–17 μmol CO2 m−2 s−1. The increasing photosynthetic capacity during 3–5 months after leaf emergence was closely related to concomitant changes in leaf N and chlorophyll contents. The possibility that N import to the leaf was a significant factor limiting the development of photosynthetic capacity is discussed.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1111/j.1399-3054.1991.tb01286.x

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Digitale Medien

Ecology of black beetle Heteronychus arator. Influence of plant species on larval consumption, utilization and growth (1981)

King, P. D. ; Mercer, C. F. ; Meekings, J. S.

Springer

Entomologia experimentalis et applicata 29 (1981), S. 109-116

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ISSN: 1570-7458

Schlagwort(e): Heteronychus arator ; Scarabaeidae ; larvae ; consumption ; utilization ; growth ; feeding ; roots ; Paspalum dilatatum ; Lolium perenne ; Trifolium repens

Quelle: Springer Online Journal Archives 1860-2000

Thema: Biologie

Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Futteraufnahme, die Futterverwertung und das Wachstum von Drittstadiumlarven von H. arator beim Fressen von Wurzeln von Paspalum dilatatum, Raygras (Lolium perenne) und Weissklee (Trifolium repens) wurden gravimetrisch gemessen. Der durchschnittliche Futterverzehrindex auf Gräsern war 0.65 mg/mg Larve/Woche verglichen mit 0.18 auf Weissklee. Die relative Wachstumsrate auf Paspalum und Raygras was 0.158 und 0.124 mg/mg Larve/Woche verglichen mit 0.043 auf Weissklee, was den geringen Verzehr an Weisskleewurzel widerspiegelt. Die Verwertung der gefressenen Wurzel war 22%, 18% und 24% für Paspalum, Ryagras und Weissklee. Das Fehlen gesicherter Unterschiede in der Futterverwertung der drei Pflanzenarten deutet darauf hin, dass die geringe Wachstumsrate auf Weissklee bloss durch geringe Futteraufnahme verursacht ist. Es wurde gezeigt, dass in Weisskleewurzel Frasinhibitoren für H. arator vorhanden sind. Die erhaltenen Schätzungen für Futteraufnahme durch Scarabaeiden sind die besten Daten für wurzelfressende Arten und liefern eine Basis, um den Einfluss der Weidepflanzen auf H. arator Populationen zu verstehen.

Notizen: Abstract The consumotion, utilization and growth of third-instar larvae of black beetle, Heteronychus arator (F.) feeding on roots of ryegrass (Lolium perenne), paspalum (Paspalum dilatatum) and white clover (Trifolium repens) were studied. Consumption was greater on the grasses than on white clover when assessed by gravimetric methods. Larvae had a higher growth rate on the grasses. Utilization of the roots of the three species was similar indicating that poor growth on white clover is the result of low consumption probably induced by the presence of feeding deterrents in the roots.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00300756

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