Hydroponic and aeroponic methods have been used to study the propagation and growth of plants (1, 2, 4). A combination of these two methods of liquid culture, aero-hydroponics, has been developed (3). Known as the Ein Gedi System (EGS), this aerohydroponics method incorporates the advantages (buffered nutrient capacity of hydroponics and water oxygenation of aeroponics) of both types of liquid culture. The objective of this study was to compare aero-hydroponics (EGS) and solid media for cutting propagation with and without overhead mist.
Cuttings of Ficus benjamina L. and Chrysanthemum × morifolium(Dendranthema grandiflora tzvelev.) were rooted in aero-hydroponics to study the effect of dissolved oxygen concentrations in the range of 8 mg·liter. (ambient saturation) to 0 mg·liter−1. The results of this study indicate that dissolved oxygen is essential to root formation and root growth. Woody (Ficus) and herbaceous (Chrysanthemum) cuttings responded similarly. Lowering the dissolved oxygen concentration increased the time required to form adventitious roots, reduced rooting percentages, reduced numbers of roots formed per cutting, and reduced average root lengths. Comparisons between stirred and unstirred water suggested the development of an area of depleted oxygen concentration (boundary layer) at the stem-water interface on cuttings immersed in unstirred water. Cuttings in water stirred constantly rooted sooner and formed more roots than did those in unstirred water. Maximum rooting occurred in misted (high dissolved oxygen concentrations) sections of cuttings suspended in the aero-hydroponics chambers. Chemical name used: potassium salt of lH-indole-3-butyric acid (K-IBA).
Lettuce plants (Lactuca sativa L.) showed definite flowering peaks over a 70-day period. Over 90% of the seed yield was from flowers which opened during the first 35 days, and seed produced from flowers opening during the first 2 flowering peaks were heavier than those produced later in the season. Seed size was not correlated with number of seeds per flower head. Seed yield and quality were not affected by early harvest or by withholding water and nutrients during the last half of the flowering period. Flowering rate, seed yield, and seed quality were not related to air temperature in the range 67 to 94°F.
Physical characteristics measured individually for each lettuce (Lactuca sativa L.) seed and its embryo were significantly correlated with seedling and plant growth (vigor) up to a certain stage, possibly heading, after which the correlations diminished. Embryo physical measurements, although slightly better correlated with subsequent vigor than seed (achene) physical measurements, were highly correlated with those of the whole seed.
Of the 5 physical measurements studied, all but length were found to be associated with early vigor. Thorough statistical analyses place seed and embryo physical characteristics in a consistent and significant order in determining vigor: weight > thickness > density (as measured by an air column) > width > length.
Lettuce, Lactuca sativa L., plants were grown in soil irrigated at various intervals with nutrient solution and in hydroponics culture. Increased nutrient level added to the soil increased seed yield but did not give a corresponding increase in seedling performance.
Hydroponically propagated seed, although heavier than soil propagated seed, were relatively poor in vigor and germinability. A positive linear correlation was found between N levels (5-15 meq) and seed yield, weight per seed, and seedling vigor. Amounts of amino acids and lipids were not positively correlated with nutrient supply, N level, or seedling vigor. Lettuce seed weight was a useful parameter in predicting seedling vigor only within a seed lot obtained from plants grown under the same environmental and nutritional conditions.