| effect of transpiration on pb uptake by lettuce and on water soluble low molecular weight organic acids in rhizosphere. | the effect of transpiration (high and low) on pb uptake by leaf lettuce and on water soluble low molecular weight organic acids (lmwoas) in rhizosphere has been studied. after two weeks of growth the plants were cultured in greenhouse for more four weeks and two days. pb(no(3))(2) solutions of different concentrations (100, 200, and 300 mg l(-1) of pb) were then added to the quartz sand pots of different plants and studies were initiated. blank experiments (without treating the quartz sand pots ... | 2006 | 16554084 |
| phytochemical phenolics in organically grown vegetables. | fruit and vegetable intake is inversely correlated with risks for several chronic diseases in humans. phytochemicals, and in particular, phenolic compounds, present in plant foods may be partly responsible for these health benefits through a variety of mechanisms. since environmental factors play a role in a plant's production of secondary metabolites, it was hypothesized that an organic agricultural production system would increase phenolic levels. cultivars of leaf lettuce, collards, and pac c ... | 2005 | 16302198 |
| nutrient solution cooling and its effect on temperature of leaf lettuce in hydroponic system. | the heat transfer characteristics of a hydroponic system were experimentally verified after theoretical establishment and the effect of nutrient solution cooling on the plant temperature was investigated. about 96 percent of the total heat flow transferred from culture bed to nutrient solution was the conductive heat through planting board and partitioning materials. the average and maximum temperatures of the leaf lettuce decreased 0.6 and 1.5 degrees c., respectively, with cooling of nutrient ... | 1996 | 11541574 |
| photosynthetic photon flux, photoperiod, and temperature effects on emissions of (z)-3-hexenal, (z)-3-hexenol, and (z)-3-hexenyl acetate from lettuce. | to investigate the effects of environment on plant volatile emissions, 'waldmann's green' leaf lettuce was cultivated under different levels of photosynthetic photon flux (ppf), photoperiod, and temperature. a modified growth chamber was used to sample plant volatile emissions nondestructively, over time, and under controlled conditions. total volatile emission rates were significantly higher from lettuce cultivated under ppf of 360 or 200 micromoles m-2 s-1 compared to 105 micromoles m-2 s-1, a ... | 1996 | 11539354 |
| chemoattraction ofbiomphalaria glabrata (gastropoda: planorbidae) to lipid standards and lipophilic factors in leaf lettuce and tetramin. | chemoattraction of individualbiomphalaria glabrata snails for lipid standards and lipophilic fractions of leaf lettuce and tetramin were studied in a petri dish bioassay. snails were more significantly attracted to a whole tetramin lipophilic fraction than that of leaf lettuce. thin-layer chromatography showed that major neutral lipid fractions in tetramin were triacylglycerols, free fatty acids, and free sterols, and in leaf lettuce were free fatty acids and a mixed free sterol-chlorophyll frac ... | 1993 | 24248713 |
| minitron ii system for precise control of the plant growth environment. | a transparent, cylindrical chamber system was developed to allow measurement of gas-exchange by small crop canopies in the undisturbed plant growth environment. the system is an elaboration of the minitron system developed previously to compare growth of small plants in different environments within the same general growth area. the minitron ii system described herein accommodates hydroponic culture and separate control of atmospheric composition in individual chambers. root and shoot environmen ... | 1988 | 11539769 |
| comparison of fluorescent and high-pressure sodium lamps on growth of leaf lettuce. | radiation from high-pressure sodium (hps) lamps provided more than a 50% increased yield (fresh and dry weight of tops) of loose-leaf lettuce cultivars grand rapids forcing and rubyconn, compared to that obtained by radiation from cool-white fluorescent (cwf) lamps at equal photosynthetic photon flux; yet, input wattage was approximately 36% less. it was postulated that the considerable output of 700 to 850 nm radiation from the hps lamp was a significant factor of the increased yield. under hps ... | 1987 | 11538250 |
| photosynthetic productivity and vibration/acceleration stress considerations for higher plants in bioregenerative systems. | the food production group of the nasa closed ecology life support systems (celss) program is conducting research to optimize production of candidate species from each of the major categories of food crop. studies are underway with soybean, wheat and potato, and leaf lettuce. our laboratory emphasizes the controlled environment production of leaf lettuce. our objective is to obtain the greatest possible production of edible lettuce biomass in the smallest possible growing space in the shortest po ... | 1984 | 11539009 |
| senescence inhibition and respiration induced by growth retardants and n-benzyladenine. | senescence of grand rapids leaf lettuce was greatly reduced at 3 storage temperatures by post-harvest treatment with n,n-dimethylaminosuccinamic acid (alar) and 2-chloroethyltrimethylammonium chloride (ccc), but not with (6)n-benzyladenine (ba). conversely, alar and ccc were inactive on broccoli while ba was markedly effective. the deterioration and discoloration of mushrooms was inhibited by alar with no effect observed from ba or ccc.the inhibition of senescence by ba and the growth retardants ... | 1966 | 16656368 |