EFFECT FROM HORIZONTALLY DIVIDING THE ROOT-SYSTEM OF WHEAT PLANTS HAVING DIFFERENT PHOSPHORUS EFFICIENCIES

The mechanisms of phosphate (P) mobilized by wheat were studied with t he typically efficient or inefficient genotypes grown in a split-pot e xperiment. The split-pot was composed of two parts, the lower part was a 2-L plastic pot containing two liters of nutrient solution and the upper,part was a PCV tube six cm in diameter by eight cm high and with a nylon net bottom. The tube which was fixed on the pot lid held 250 g quartz sand. In the lid was drilled a small hole in order to add cul ture solution and 3% hydrogen perioxide (H2O2) instead of aerating. Tw o seedlings were planted in the quartz sand of each of the tubes. Ponn amperuma's recipe was used for preparing the culture solution For each of the three genotypes tested, four P treatments were: (i) with 0.5 g TCP as the only P source added to the solution, (ii) with 0.5 g TCP a s the only P source added in quartz sand, (iii) without any P, and (iv ) the check (CK). Sodium dihydrogen phosphate (NaH2PO4) was the P sour ce in culture solution. When tricalcium phosphorus (TCP) was added to the solution, the amount of calcium (Ca) taken up by the efficient gen otype, Lovrin 10, was 2.7 and 3.6 times higher than those of the ineff icient ones, Chinese Spring and 80-55. Also, the amount of P mobilized and released by Lovrin 10 was 30% and 77% higher than those of the ot her two genotypes. When TCP was added in the quartz sand, the genotypi cal differences in Ca influx or P mobilization had the same tendency a s above. Chinese Spring and 80-55 could not complete their life cycle. However, Lovrin 10 not only flowered but bore fruit as wen, indicatin g absorption of more Ca and active mobilization of P were the basic ch aracters of the efficient genotype, Lovrin 10.