Effect of Potassium Deficiency upon Translocation of ¹⁴C in Detached Blades of Sugarcane

Abstract

The translocation of radioactive photosynthate was studied in blades detached from plants which had been grown in nutrient solution with and without potassium. Basipetal translocation decreased in the blades of plants deprived of potassium, even when deficiency symptoms were not visible. In such slightly potassium-deficient leaves, translocation was decreased in the light but not in the dark. More severe potassium deficiency decreased translocation both in darkness and in light. Potassium deficiency decreased translocation at light intensities giving no difference in rate of photosynthesis between plus and minus potassium leaves and even at light intensities at which there was no net fixation of carbon dioxide. At all levels of deficiency, the relative decrease in translocation was greater than the relative decrease in photosynthesis. Translocation was affected at potassium deficiency levels which had no effect upon photosynthesis.Potassium deficiency decreased translocation relatively more than it decreased moisture content. There was a much better correlation between the decrease in potassium and translocation than between the decrease in moisture and translocation.An experiment with radioactive phosphorus indicated an upset in phosphorylation in the stems of potassium-deficient plants.Experiments reported in the preceding paper (9) led to the conclusion that K may exert a direct effect upon translocation of photosynthate. This conclusion was confirmed and strengthened by studies with detached blades reported herein.K is not the only nutrient required for translocation, since deficiencies in N and P also decrease the transport of sugar in the sugarcane plant (6, 11). MATERIALS AND METHODSThe varieties of sugarcane studied in these experiments were previously described (9).Shoots grown from stem cuttings cultured in volcanic black sand for 2.5 months were transplanted to tap water culture, two plants per 16-liter pot or one per 8-liter pot. After about 1 month in tap water, the plants were supplied with nutrient solutions prepared with distilled or deionized water. The complete solution contained K; the -K solution contained no K (9).All of the methods of application of "CO2, sampling, analysis, and radioactivity counting were the same as with attached blades, the only difference being that the system under investigation was a detached blade rather than an entire plant, a system with several advantages (12).Blades were cut from the plant at about 8 AM, recut twice under water, and taken to the air-conditioned room. The cut end of the blade remained in water during the entire test. After preillumination, measured doses of 14CO2 were supplied to portions of the blades for 5 min in artificial light. The feeding chamber (6, 15) was quickly removed, and the blade was placed under the illumination desired for translocation. The portion of the blade above the fed part is called the apex; that below the fed part, the base.Translocation took place for 6 or 24 hr, after which each blade was cut into measured sect...

Effect of Nitrogen Deficiency upon Translocation of 14C in Sugarcane

“…Factors affecting translocation of 'IC in sugarcane include supply of K, N, and P (8,10,11 and whether the N is supplied as NO3-or NH4+ (2,5). N nutrition may also affect the composition of the translocate (16).…”

“…Factors affecting translocation of 'IC in sugarcane include supply of K, N, and P (8,10,11). Although the transport of sugar takes place in living cells and may depend upon enzyme action (15), few experiments have been reported dealing with the effect of N nutrition upon translocation of carbohydrates, especially those labeled with "4C.…”

“…In the sheath, however, the control had more labeled sucrose. Thus, N deficiency, like K and P deficiencies (8,10,11), prevented the translocation of sucrose, not because there was no sucrose available for translocation, but for some other reason.…”

“…Although withholding nitrogen decreased translocation of labeled carbon in and from attached blades, there was no effect upon transport in detached blades. The effect of nitrogen deficiency upon translocation may be indirect and secondary to the effect upon growth of the plant as a whole.Factors affecting translocation of 'IC in sugarcane include supply of K, N, and P (8,10,11 and whether the N is supplied as NO3-or NH4+ (2,5). N nutrition may also affect the composition of the translocate (16).…”

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

“…A relationship between phosphorylation and translocation has been suggested by several investigators (11,24, and others). K deficiency decreased both phosphorylation and translocation (17,18). The low light intensity saturation of phototranslocation in sugarcane (15) resembles that of light-enhanced absorption of K+ (28) and Cl- (25) as well as of photoassimilation of glucose by Chlorella (22.…”