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  • Author or Editor: D. A. Smittle x
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Nitrogen applied as NH4-N or NO3-N (75 mg·liter-1) affected onion (AIlium cepa L.) plant growth when grown in solution culture. Nitrate alone or in combination with NH4-N increased leaf fresh and dry weight, leaf area, root fresh and dry weight, and bulb dry weight when compared to growth with NH4-N as the sole N source. Bulb fresh weight was highest with an NH4-N: NO3-N ratio between 1:3 and 3:1. Maximum leaf fresh weight was not necessary to produce maximum bulb fresh weight when onions were subjected to different N-form ratios. Precocious bulbing resulted when NH4-N was the sole N source; however, high bulbing ratios early in plant development were not correlated with final bulb fresh weight. Nitrogen form also influenced water uptake and pungency, as measured by enzymatically developed pyruvate concentration, but did not affect bulb sugar concentration.

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Ethylene is produced by cucumber fruits (Cucumis sativus L.), at a rate which is size dependent. Small fruits (<2.6 cm diam) produced substantially more ethylene/kg fruit than did large fruits (2.6-3.8 and 3.8-5.1 cm diameter). Respiration was similarly affected. Mechanically harvested fruits produced 2 to 3 times more ethylene than did hand-harvested fruits. Texture profile analysis (TPA) of cross-sections of fruits treated 48 hr with 0, 0.1, 0.5, 1.0, 5.0 and 10.0 µl/liter ethylene indicated little change in textural parameters at concentrations below 10.0 µl/liter. Ethylene treatment, especially high concentrations, decreased fruit chlorophyll content. Greatest chlorophyll loss was at the stem-end of the fruit. Ambient concentrations of ethylene in well-ventilated trucks of cucumbers were not great enough to present a quality problem for processing cucumbers.

Open Access

`Rio Verde' cabbages (Brassica oleracea L.) were grown in drainage lysimeters on two soil types (Tifton loamy sand and Bonifay sand) in the spring and the fall of 1982, 1983, and 1985. Irrigation regimes consisted of applying water amounts equal to soil water deficit when the soil water tension at a 10-cm depth exceeded 25, 50, or 75 kPa throughout growth of the crops. Because the lysimeters were equipped with rainfall-activated shelters, water applications and evapotranspiration (ETc) were similar. Crop factors (CF) as functions of plant age (i) were computed for all combinations soil type-season-irrigation regime as the ratio between water applications and class A pan evaporation (Ep). No significant differences were observed among soil type or season, but irrigation regimes significantly affected ETc and CF(i). The highest ETc and leaf yields corresponded to the 25-kPa regime. CF(i)=0.025i - 0.0002li2, 0.023i - 0.00017i2, and 0.022i - 0.00017i2, for the 25-kPa, 50-kPa, and 75-kPa treatments, respectively (R2=0.97). Therefore, daily ETc by cabbages can be computed with Ep as ETc = CF(i) × Ep for scheduling irrigation.

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