Plant requirements for N exceed all other mineral elements with typical tissue concentrations ranging between 2% and 5% of dry weight depending on plant species and development stage (Marschner, 1995). Plants deficient in N typically exhibit overall stunted growth and chlorotic leaves. Common causes of N deficiency are from inadequate fertilization regimes; the amount supplied is too low to meet a plant's demands at a specific developmental stage, an error occurred in the initial fertilizer mixing rate, nutrients are leached from the substrate by excessive irrigation, or an injector malfunctions. Excluding mechanical adjustments to equipment, recommendations for correcting N deficiency suggest higher rates or more frequent fertilizer applications (Dole and Wilkins, 2005; Whipker et al., 2001).
Augmenting N supply to N-starved plants has been shown to promote recovery in certain plant functions. On reintroduction, increased nitrate uptake rates were observed over 24 h, 48 h, and 3 d for wheat (Triticum vulgare Vill. cv. Knox), perennial ryegrass (Lolium perenne L.), and barley (Hordeum vulgare L.), respectively (Bowman and Paul, 1988; Jackson et al., 1976; Lee and Rudge, 1985). Photosynthetic rates resumed normal capacity in 10 d for corn (Zea mays L.), whereas chlorophyll content partially recovered over the same time period when resupplied with N (Girardin et al., 1985). Although total dry weight more than doubled after growing 10 d in N-free solution and a 15-d recovery period for soybean (Glycine max L.), ending shoot weight values were still only 50% of non-stressed plants (Tolley-Henry and Raper, 1986).
In commercial greenhouse production, seedling crops such as geranium follow rigid schedules for plug production. Disruption in the supply of essential elements over any time period during the production schedule may delay the readiness of a crop for shipment or may cause irreversible damage, rendering a crop unmarketable. Although it has been shown that plant functions can recover from N deficiency in other crops, little research has investigated the threshold beyond which a bedding plant crop is unrecoverable. The objective of this research was to determine the effect of N deficiency on geranium chlorophyll content and growth and then to document the degree of recovery and recovery time from N deprivation.
Boussadia, O., Steppe, K., Zgallai, H., Ben El Hadj, S., Braham, M., Lemeur, R. & Van Labeke, M.C. 2010 Effects of nitrogeN-deficiency on leaf photosynthesis, carbohydrate status and biomass production in two olive cultivars ‘Meski’ and ‘Koroneiki’ Sci. Hort. 123 336 342
Bowman, D.C. & Paul, J.L. 1988 Uptake and assimilation of NO3 - and NH4 + by nitrogen-deficient perennial ryegrass turf Plant Physiol. 88 1303 1309
Girardin, P., Tollenaar, M. & Muldoon, J.F. 1985 Effect of temporary N starvation on leaf photosynthetic rate and chlorophyll content of maize Can. J. Plant Sci. 65 491 500
Le Bot, J., Jeannequin, B. & Fabre, R. 2001 Impacts of N-deprivation on the yield and nitrogen budget of rockwool grown tomatoes Agronomie 21 341 350
Lee, R.B. & Rudge, K.A. 1985 Effects of nitrogen-deficiency on the absorption of nitrate and ammonium by barley plants Ann. Bot. (Lond.) 57 471 486
Mak, A.T. & Yeh, D.M. 2001 Nitrogen nutrition of Spathiphyllum ‘Sensation’ grown in sphagnum peat and coir-based media with two irrigation methods HortScience 36 645 649
Mattson, N. & Lieth, H. 2008 ‘Kardinal’ rose exhibits growth plasticity and enhanced nutrient absorption kinetics following nitrate, phosphate, and potassium deprivation J. Amer. Soc. Hort. Sci. 133 341 350
Singh, M.P. & Saxena, P.K. 1994 Deficiency and excess feeding signs of macro-elements on mango (Mangifera indica L) cv. Dashehari Recent Hort. 1 30 35
Tolley-Henry, L. & Raper, C.D. Jr 1986 Nitrogen and dry-matter partitioning in soybean plants during onset and recovery from nitrogen stress Bot. Gaz. 147 392 399
Whipker, B.E., Dole, J.M., Cavins, T.J., Gibson, J.L., Fonteno, W.C., Nelson, P.V., Pitchay, D.S. & Bailey, D.A. 2001 Plant root zone management North Carolina Commercial Flower Growers’ Association Raleigh, NC
Zhao, D., Reddy, K.R., Kakani, V.G., Read, J.J. & Carter, G.A. 2003 Corn (Zea mays L.) growth, leaf pigment concentration, photosynthesis and leaf hyperspectral reflectance properties as affected by nitrogen supply Plant Soil 257 205 217