
TY  - JOUR
A1  - Spencer, K 
A1  - Chan, CW 
T1  - Critical phosphorus levels in sunflower plants
JF  - Australian Journal of Experimental Agriculture
JO  - Aust. J. Exp. Agric.
Y1  - 1981
VL  - 21
IS  - 108
SP  - 91
EP  - 97
KW  - 
UR  - https://doi.org/10.1071/EA9810091 
N2  - To provide a basis for a tissue test for the diagnosis of P deficiency in sunflower crops, the influence of plant part and age on the critical P percentage (P concentration in tissues required to sustain 90% of maximum yield) was examined. In a glasshouse experiment, the known mobility of phosphate within the plant was reflected in the occurrence of the highest P concentration in the youngest leaves. Laminae contained more P than petioles on a dry-weight basis. Stem internodes contained less P than the adjoining petiole near the base ofthe plant but more near the apex. Three field experiments indicated that the lamina of the youngest fully-expanded leaf was a suitable plant part for diagnosis. Critical P concentrations for this tissue decreased from about 0.35% at the fourth week from sowing to 0.20% at the tenth week. 
ER  -

