Novel Method of Supplying Nutrients Permits Predictable Shoot Growth and Root : Shoot Ratios of Pre-transplant Bedding Plants

BACKGROUND AND AIMS: Growth of bedding plants, in small peat plugs, relies on nutrients in the irrigation solution. The object of the study was to find a way of modifying the nutrient supply so that good-quality seedlings can be grown rapidly and yet have the high root : shoot ratios essential for e...

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Bibliographic Details
Published in:Annals of botany 2007, Vol.99 (1), p.171-182
Main Authors: Greenwood, Duncan J, Mckee, John M.T, Fuller, Deborah P, Burns, Ian G, Mulholland, Barry J
Format: Article
Language:English
Subjects:
Bedding
Coefficients
Environment
Fertilizers
Gardening - methods
Models, Biological
Nutritional deficiencies
Original
Petunia
Petunia - growth & development
Petunia hybrida
Plant growth
Plant nutrition
Plant roots
Plant Roots - growth & development
Plant Shoots - growth & development
Plants
Ratios
Root growth
Salmonidae
Seedlings
Viola
Viola - growth & development
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Summary:BACKGROUND AND AIMS: Growth of bedding plants, in small peat plugs, relies on nutrients in the irrigation solution. The object of the study was to find a way of modifying the nutrient supply so that good-quality seedlings can be grown rapidly and yet have the high root : shoot ratios essential for efficient transplanting. METHODS: A new procedure was devised in which the concentrations of nutrients in the irrigation solution were modified during growth according to changing plant demand, instead of maintaining the same concentrations throughout growth. The new procedure depends on published algorithms for the dependence of growth rate and optimal plant nutrient concentrations on shoot dry weight Ws (g m⁻²), and on measuring evapotranspiration rates and shoot dry weights at weekly intervals. Pansy, Viola tricola 'Universal plus yellow' and petunia, Petunia hybrida 'Multiflora light salmon vein' were grown in four independent experiments with the expected optimum nutrient concentration and fractions of the optimum. Root and shoot weights were measured during growth. KEY RESULTS: For each level of nutrient supply Ws increased with time (t) in days, according to the equation ΔWs/Δt=K₂Ws/(100+Ws) in which the growth rate coefficient (K₂) remained approximately constant throughout growth. The value of K₂ for the optimum treatment was defined by incoming radiation and temperature. The value of K₂ for each sub-optimum treatment relative to that for the optimum treatment was logarithmically related to the sub-optimal nutrient supply. Provided the aerial environment was optimal, Rsb/Ro[almost equal to]Wo/Wsb where R is the root : shoot ratio, W is the shoot dry weight, and sb and o indicate sub-optimum and optimum nutrient supplies, respectively. Sub-optimal nutrient concentrations also depressed shoot growth without appreciably affecting root growth when the aerial environment was non-limiting. CONCLUSION: The new procedure can predict the effects of nutrient supply, incoming radiation and temperature on the time course of shoot growth and the root : shoot ratio for a range of growing conditions.
ISSN:0305-7364
1095-8290
DOI:10.1093/aob/mcl240