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EFFECT OF pH IN FLOWING NUTRIENT SOLUTION ON THE GROWTH AND PHOSPHATE UPTAKE OF WHITE CLOVER SUPPLIED WITH NITRATE, OR DEPENDENT UPON SYMBIOTICALLY FIXED NITROGEN
Author(s) -
BREEZE V. G.,
EDWARDS D. G.,
HOPPER M. J.
Publication year - 1987
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.1987.tb04794.x
Subject(s) - nitrogen , nitrate , phosphate , chemistry , nitrogen fixation , nutrient , phosphorus , shoot , dry weight , nitrogen deficiency , agronomy , horticulture , botany , biology , biochemistry , organic chemistry
S ummary The effect of solution pH (at values of 4.0, 5.0, 6.0 and 7.0) and nitrogen source (plants supplied with nitrate, or dependent upon symbiotically fixed nitrogen) was examined for 56 d old nodulated white clover plants grown in flowing nutrient culture of controlled composition. Sequential harvests were made during the following 20 d period. No statistically significant effect of solution pH or nitrogen source was noted on dry weight, although plants grown at pH 4 were generally slightly smaller than the other plants. Within 5 d of the start of treatments, plants supplied with nitrate had higher fresh weights than those dependent on nitrogen fixation, and plants grown at pH 4 had smaller fresh weights than those grown at pH 5, 6 and 7. The response by fresh and dry weights to solution pH was not affected by nitrogen source. The amount of nitrogen fixed by plants grown at pH 4 was about 20% less than at pH 5, 6 and 7. Both shoots and roots of plants grown at pH 4 had lower phosphorus concentrations for both sources of nitrogen than the plants grown at pH 5 and above. Roots of plants dependent on nitrogen fixation at pH 5, 6 and 7 had much higher phosphorus concentrations than plants supplied with nitrate. Initially, phosphate uptake by plants dependent on nitrogen fixation exceeded that of plants supplied with nitrate at all pH values. Towards the end of the experimental period, uptake was greater by plants supplied with nitrate. For the 20 d experimental period, phosphate uptake was greatest at pH 5, followed by pH 6, 7 and 4 for plants supplied with nitrate, whereas for plants dependent on symbiotically fixed nitrogen, uptake was greatest at pH 7, followed by 6, 5 and 4; there was no difference between phosphate uptake with the two sources of nitrogen at pH 7.