Core Ideas Diagnostics of mineral nutrition in field is poorly developed for potato group Andigenum. Critical dilution curves for N, P, and K were validated in potato group Andigenum. The critical dilution curve serve to identify macronutrient status and to predict yield of potato in the tropics. The critical dilution curves (CDC) for nitrogen (Nc), phosphorus (Pc), and potassium (Kc) obtained from total dry biomass (W) and leaf area index (LAI) were used as a diagnostic tool to determine nutrient status and to adjust fertilization rates in two cultivars of potato (Solanum tuberosum L.) group Andigenum. The research determined allometric ratios of Nc, Pc, and Kc (%) and nutrition index (NI) based on W and LAI in cultivars Diacol Capiro (Capiro) and Pastusa Suprema (Suprema). Additionally, optimal fertilization rate was evaluated to achieve maximum yields during two growth cycles in contrasting environments of the Andean zone of Colombia. The CDC was validated using W in Capiro: Nc = 6.23W −0.320; Pc = 0.523W −0.198; Kc = 9.02W −0.269 and in Suprema: Nc = 6.74 W −0.327; Pc = 0.536W −0.186; Kc = 6.58W −0.135 and presented higher robustness than the CDC obtained from LAI. Capiro presented a lower dilution coefficient b for Kc than Suprema. The NI ranged between 0.25 and 1.32 with better fit in Capiro and relative yields (RY) starting from 40% without fertilization; for Suprema, null to marginal response to fertilization was obtained, indicating a luxury uptake of N (NI 1–1.5) with RY starting from 70%. Except for this research, Nc, Pc, and Kc have not been validated for cultivars of group Andigenum. The CDC for this cultivated group could serve to identify deficiency, sufficiency, or excess of N, P, and K, and to predict final yield per cultivar under highland equatorial conditions.

Distribution of iron (Fe), manganese (Mn), and zinc (Zn) in mature grains of maize (Zea mays L.) of 25 genotypes was studied. The highest concentrations of micronutrients were found in the seed coats and scutellum, while the lowest were found in the endosperm. The endosperm, scutellum, and seed coats contained between 60-80%, 15-35%, and 8-12% of the total grain micro-JOURNAL OF PLANT NUTRITION, 25(3), 635-653 (2002) 635 ORDER REPRINTS nutrients, respectively. Mobilization of Fe, Mn, and Zn from the scutellum and endosperm was studied in four genotypes of maize during 3-120 h of germination and early seedling growth. Variation in original concentrations in the scutellums of the genotypes exceeded that observed in the endosperms. Genotypes were separated into several groups with high-Fe (144-168 mg g À1 ) and high-Zn (89-94 mg g À1 ) scutellum (cvs. Brewero yellow, Corriente de gallina), high-Mn (40-42 mg g À1 ) scutellum (cvs. Pusey blond, Brewero yellow), low-Fe (107-110 mg g À1 ) and low-Zn (76 mg g À1 ) scutellum (cvs. Pusey blond, Oregon grewn), and low-Mn (33-36 mg g À1 ) scutellum (cvs. Oregon grewn, Corriente de gallina). The type of kernel tissue influenced micronutrient mobility during germination. The highest share of freely leaked forms of micronutrients was generally observed for the genotypes with high-micronutrient scutellum. After the radicle protruded, the efflux of micronutrients from the scutellum was not dependent with original metal concentrations. The genotypes studied did not differ in the total efflux of minerals from the grain (endosperm þ scutellum) measured 120 hr after grain soaking. The following sequence characterized efficiency of kernel-born metals utilization by the seedling: Fe < Mn ! Zn. Efficiency of mobile Zn utilization was specific to the growth of genotype. This index was found lowest for cvs. Brewero yellow and Pusey blond with low-weight seedlings. Removal of seed coats after 3 days of grain soaking did not influence dynamics of micronutrients in grains and seedlings of cv. Mestnaya. The possible pathways of micronutrient transport in seedlings are discussed in relation to original micronutrient distribution within the grain.

Shoot stretching in plug production reduces quality and makes mechanized transplanting difficult. The objectives of this study were to measure seedling emergence and shoot height of plugs as affected by paclobutrazol application during seed soaking, priming, or coating on seedling emergence and height. Verbena (Verbena ×hybrida Voss. `Quartz White'), pansy (Viola wittrockiana L. `Bingo Yellow Blotch'), and celosia (Celosia cristata L. `New Look') seeds were soaked in water solutions of paclobutrazol and subsequently dried on filter paper at 20 °C for 24 h. Soaking seeds in paclobutrazol solutions before sowing reduced growth and percentage seedling emergence of verbena and pansy but had little effect on those of celosia. Verbena seeds soaked in 50, 200, or 500 mg paclobutrazol/L for 5, 45, or 180 min produced fewer and shorter seedlings than controls. Osmopriming verbena seeds with 10 to 500 mg paclobutrazol/L reduced seedling emergence. Seedling height and emergence percentage of pansy decreased with increasing paclobutrazol concentrations from 2 to 30 mg·L–1 and with soaking time from 1 to 5 min. The elongation of celosia seedlings was reduced by soaking seeds in 10, 50, 200, or 500 mg paclobutrazol/L solutions for 5, 180, or 360 min. However, these reductions were negligible and without any practical application.

No abstract

Determination of plant growth regulator accumulation in fruits and vegetables for human consumption is an important safety issue even when it is applied to seeds. Paclobutrazol accumulated preferentially in the seedcoats when soaking cucumber (Cucumis sativus L., cv. Poinsett 76SR) seeds in 1000 or 4000 mg·L–1 paclobutrazol. Cucumber plants grown from seeds soaked in 1000 mg·L–1 paclobutrazol had lower average fruit weights than the control plants. Individual fruit length in cucumber was reduced by 40% when seeds were soaked in 1000 mg·L–1 paclobutrazol solutions for 180 minutes. Soaking tomato (Solanum lycopersicum L., cv. Sun 6108) seeds in 0 to 1000 mg·L–1 paclobutrazol did not reduce average fruit weight or diameter per treatment. Paclobutrazol residue was not detected in cucumber and tomato fruits harvested from plants grown from seeds soaked in 1000 mg·L–1 paclobutrazol for 180 minutes. Soaking seeds in paclobutrazol solutions represents a promising method of applying plant growth regulators to tomato and cucumber without accumulation of paclobutrazol residue in fruits.