Potassium Retranslocation in Seedlings of Hordeum Vulgare

Abstract

SummaryMeasurements have been made both on the uptake of potassium and potassium isotope from a nutrient solution and their redistribution within barley plants. During the experimental period the seedlings had three leaves which represented different stages in leaf development, i.e. from the mature to the rapidly developing stage.The results showed that substantial retranslocation of potassium within the plant took place. Translocation was most evident in the mature leaf which exported at least 1·6 Wequiv. per day but showed little potassium uptake. About 50% of the potassium taken up by the rapidly developing youngest leaf was shown to be derived from within the plant, the net uptake being 3· 5 fL·equiv. per day.The movement of potassium within the plant is discussed in relation to known net movements of potassium. The mechanisms of potassium uptake by different leaves and its subsequent retranslocation are briefly considered. Possibilities of competition between different tissues are particularly emphasized.

Uptake and Transport of Ions in Barley Seedlings III. Correlation Between Transport to the Shoot and Relative Growth Rate

“…(This difference is due to translocation of potassium in the phloem from old to younger leaves.) However, the ratio of potassium to sodium in the shoot as a whole remains constant despite these differences between leaves (Pitman 1965a;Greenway and Pitman 1965). In barley seedlings the shoot thus behaves as a whole organ.…”

“…The level of potassium in the leaf cells is assumed to be maintained by active transport from the free space. The leaf as a whole receives ions from the xylem and can export potassium (preferentially to sodium) in the phloem, mainly to younger leaves (Greenway and Pitman 1965), but also to the roots. The level of ions in the free space of the leaves will be determined by the balance between these three processes (see also Robinson 1971).…”

“…Both transport and growth were stopped when plants were put from light to dark (Pitman 1965a). Similarly, there was correlation between rate of transport of potassium and chloride and the changing relative growth rate at different stages of development from germination to flowering (Greenway 1965;Greenway et al 1965).…”

Calcium and Magnesium Uptake by Barley Seedlings

“…Seedlings were grown on culture solutions which were basically the sarpe as described in previous publications (Pitman 1965a(Pitman , 1965bGreenway and Pitman 1965). The solutions were modified by varying levels of Ca(NOah and MgS04; the concentrations used in each experiment are given in the text and "a solution containing 10 m-equiv/l Ca(NOah" means a culture solution with all other nutrients at the standard level but with Ca(NOa)2 at 10 m-equiv/l.…”

Studies on Improving Fruit Yield and Quality of Peach CV. "Early sweeling"

“…It is well known that, many studies indicated that spraying some deciduous trees with Ca, K and CPPU either alone or in combination has been used successfully as an applicable mean for enhancing fruiting parameters through increasing fruit set, reducing fruit drop and improving both fruit characteristics and leaf nutritional status, which reflects finally on yield and quality, (Mansour et al (1986) on peach, Greenway and Pitman (1965) and Greene (1996) on apples, Bisal et al (1991) Kiwi fruits, Feng et al (1999), Marwad (2001) and Ben-Arie et al (2008) on seedless and seeded grapes, Tzoutzoukou and Bonranis (1997) on apricot, Moon et al (2000), Guriguis et al(2003) and on pear trees and and Abd El-Fatah et al (2008) on persimmon trees).…”