Factors Affecting Absorption and Translocation of Foliar Applied Phosphorus.

Abstract

Phosphorus is known to be exported from leaves of apple (8,9,10), bean (4,6,11,12,13), chrysanthemum (1, 2), corn (11,12), tomato (12) and squash (71). The present work with bean plants compares export following application by spray, leaf vein injection (4) and droplet (13) methods. Other factors investigated which affect absorption and subsequent translocation of the spray-applied phosphorus include: 1) wetting agents, 2) phosphorus concentration of the spray, 3) leaf surface (upper vs lower surface), 4) different phosphorus compounds (pH and cation), 5) time, 6) hygroscopic agent, 7) size of area sprayed, 8) age and position of sprayed leaf, and 9) phosphorus level of the plant. METHODSRed Kidney bean plants grown in one-half strength Hoagland solution under fluorescent lights on a 6:00 A.2I. to 6:00 P.NI. day were used throughout. The light intensity, temperature and relative humidity were 1000 ft-c (as measured half-way up the stem), 240 ± 1°C and 60 % + 4 %, respectively. At least two plants were used for each treatment. To obtain more uniform plants, the axillary buds were removed before vascularization was pronounced, 2 and 3 days before treatment.The phosphorus solutions containing 0.2 ml of P32-labeled phosphorus of known specific activity were sprayed onto the upper surface of the terminal leaflet of the first trifoliate leaf, unless stated otherwise, between 9:00 and 11:00 A.NM. when the plants were 18 days old (12 days after the hypocotyls had straightened). To prevent contamination of the remainder of the plant the leaflet receiving the spray was enelosed in a clear plastic box which was removed several minutes after treatment. Except in the time eourse of uptake experiments, the plants were harvested and sectioned 24 hours after the application of the tracer. Usually each plant was sectioned into three parts: 1) the sprayed leaflet, 2) the remaining two leaflets and petiole of the first trifoliate leaf, 3) and the remainder of the plant. In some cases the remainder of the plant was divided at the node of the first trifoliate leaf to obtain the upward and (lownward movement. The amount of phosphorus applied was determined by summation. The percentage of applied phosphorus which moved into the nutrient solution was negligible (about 0.03 %) and was not determined in most experiments.

Translocation of Calcium in the Bean Plant.

“…The approximate values for calcium and phosphorus translocation, the latter applied as NaH2P3204, was 0.02 and 15 MAg respectively, or a ratio of 1 : 750. The spray concentration resulting in the most efficient translocation of calcium was between 50 and 100 mM (fig 4) whereas for phosphorus it appeared to be between 10 and 30 mM (9). At the BIDDULPH ET AL-TRANSLOCATION OF CA IN BEANT PLANT 0.06 ug of Ca and 6 ,ug of P were translocated-a ratio of 1 : 100.…”

“…This is the highest phosphorus concentration available for comparison (9). The approximate values for calcium and phosphorus translocation, the latter applied as NaH2P3204, was 0.02 and 15 MAg respectively, or a ratio of 1 : 750.…”

Translocation of Carbon-14 in Sugarcane Plants Supplied with or Deprived of Phosphorus

“…An effect of P deficiency upon translocation was reported in 1956 when Rohrbaugh and Rice (30) noted that 2,4-D (or perhaps a metabolic product of 2,4-D) is not readily translocated through tomato plants seriously deficient in P. Koontz and Biddulph (23) stated that apparently the translocation of P is impaired in P-deficient plants. Since the movement of P in the phloem is correlated with food movement in the plant (9), the translocation of food could be assumed to be impaired in P-deficient plants.…”

Foliar application of phosphorus compounds

“…It prevents sprays from drying completely on the leaf surface. Koontz and Biddulph (1957) reported that glycerin increased the translocation of phosphorus. Fisher and Walker (1955) reported a sevenfold increase in phosphorus absorption when 2.% glycerin was added to the spray solution.…”

“…Koontz and Biddulph (1957) Koontz and Biddulph (1957), and Rid (1964) all found that spraying in the evening is the best because of slowest drying. Dew formation in the morning remoistens the residue of nonabsorbed salt.…”