الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
In the present investigation the photosynthetic activity(14Go2-iight fixation) and some related metabolic processes taiorophyii biosynthesis, carbohydrates and nitrogen assimilat-ION) , of bean, tomato and maize plants, as influenced by phosphorus magnesium - and potassium levels, were studied* fe following points were reached.
1- Low levels of phosphorus resulted in slight suppression of the total- and TGA soluble carbohydrates content in bean plants. In case of tomato these low levels resulted in a considerably low soluble carbohydrate fraction and high insoluble one. In maize the carbohydrates content fluctuated irregularly
labelling into a soluble fraction was found in phosphorus deficient bean and tomato.
Phosphorus deficiency was mostly accompanied by a relative decrease in percentage labelling of phosphorylated sugars and reifeed compounds. Bean and tomato plants cultured at low level of phosphorus incorporated relatively low labelling percentage into aspartic acid and high labelling percentage into glutamic acid. In maize the reverse action was observed. Sucrose was found to be labelled only in maize plants cultured in nutrient media having sufficient phosphorus.
magnesium
Magnesium deficient bean and tomato slightly accumulated TGA soluble carbohydrates which diminished considerably with the rise of magnesium levels. In maize, on theother hand magnesium deficiency resulted in a significantly low carbohydrates content which progressively increased with the rise of magnesium level.
Magnesium deficient tomato accumulated soluble nitrogen, while magnesium deficient maize accumulated insoluble and total nitrogen. In bean plants the nitrogen fraction snowed irregular trend. Magnesium deficient plants exhibited generally low pigment content, which became more evident with the plant age. With tne rise of magnesium levels the chlorophyll content
at different levels.
I Phosphorus deficient plants accumulated more soluble
nitrogen at the expense of the TOA insoluble fraction which was generally diminished.
Phosphorus deficient bean plants exhibited relatively high pigment content, which was mostly due to the relative high content of chlorophy. Q3iis response became more evident with the plant age* However, in case of tomato and maize no regular trend was observed-Phosphorus deficiency did not severely reduce the rate of
10 assimilation in bean leaves but it suppressed those in tomato and maize considerably. A relative accumulation of
increased considerably.
Magnesium deficiency exerted almost no effect on bean photosynthetic activity, but those of tomato and maize were s suppressed.
- Magnesium deficiency was of moderate influence on the 14
pattern of Go^-fixation. However glutamic acid exhibited relatively low labelling percentage at low magnesium levels in bean and high labelling percentage in tomato. In maize the three main labelled intermediates, malic, aspartic and glutamic acids gained more or less constant labelling percentages in plants cultivated at different magnesium levels.
Potassium deficient bean and maize exhibited generally a very low carbohydrates content which progressively increased with the rise of potassium levels* An accumulation of the soluble carbohydrates fraction at the expense of the insoluble one was observed in potassium deficient tomato.
Potassium deficient bean and tomato accumulated nitrogen,
which decreased with the rise of potassium levels. A accumulation of soluble nitrogen fraction at the expense of
the insoluble one was observed in potassium deficient tomato
and maize.