G. Pulgar et al., PYRUVATE-KINASE ACTIVITY AS A BIOINDICATOR OF CATIONS IN GRAFTED WATERMELON PLANTS, Communications in soil science and plant analysis, 27(5-8), 1996, pp. 1027-1046
Three cultivars of Cucurbita pepo L. were used as rootstocks (Brava, S
hintoza and Kamel), and as scion part, four cultivars of Citrullus lan
atus (Trumb) Mansfield (Sugar King, Early Star, Dulce Maravilla, and S
ugar Bell) were grafted and subjected to the determination of calcium
(Ca), potassium (K), sodium (Na), and magnesium (Mg), and pyruvate kin
ase activity in leaves. Control plants (not grafted) gave the highest
level of total K with respect to the other cultivars. The cross Brava
x Sugar Bell showed the higher K level, while the lowest was found wit
h the cross Brava x Sugar King. Total sodium (Na) content did not show
differences within the experimented crosses as 0.77 mg Na/g d.w. was
obtained for all cultivars, while control plants gave levels of Na fiv
e times higher (3.49 mg/g d.w.). The cultivar Sugar King had the highe
st Ca integration capacity, whereas Dulce Maravilla showed a decrease,
both with respect to the control plants. The results of soluble Mg we
re lower than those obtained in the control plants, the higher concent
ration of this cation was observed in Kamel x Dulce Maravilla, while S
hintoza x Dulce Maravilla and Sugar Bell had the lower level of Mg wit
h respect to the control. The endogenous activity of pyruvate kinase (
PK) was higher in the grafted plants than the control plants. The essa
ys in the presence of Mg or K induced an increase in the PK activity o
ver the endogenous one. The results of the PK essay in the presence of
Ca were higher with respect to the previous essays. It seems that gra
fted plants have a physiological deficiency, especially for Mg and K,
whereas Ca had excessive concentrations, but some crosses showed a phy
siological demand for active Ca.