Cj. Li et al., EFFECT OF APEX EXCISION AND REPLACEMENT BY 1-NAPHTHYLACETIC ACID ON CYTOKININ CONCENTRATION AND APICAL DOMINANCE IN PEA-PLANTS, Physiologia Plantarum, 94(3), 1995, pp. 465-469
As known from literature lateral buds from pea (Pisum sativum) plants
are released from apical dominance when repeatedly treated with exogen
ous cytokinins. Little is known, however, about the endogenous role of
cytokinins in this process and whether they interact with basipolar t
ransported IAA, generally regarded as the main signal controlling apic
al dominance. This paper presents evidence that such an interaction ex
ists. The excision of the apex of pea plants resulted in the release o
f inhibited lateral buds from apical dominance (AD). This could be ent
irely prevented by applying 1-naphthylacetic acid (NAA) to the cut end
of the shoot. Removal of the apex also resulted in a rapid and rather
large increase in the endogenous concentrations of zeatin riboside (Z
R), isopentenyladenosine (iAdo) and an as yet unidentified polar zeati
n derivative in the node and internode below the point of decapitation
. This accumulation of ZR and iAdo, was strongly reduced by the applic
ation of NAA. The observed increase in cytokinin concentration precede
d the elongation of the lateral buds, suggesting that endogenous cytok
inins play a significant role in the release of lateral buds from AD.
However, the effect of NAA on the concentration of cytokinins clearly
demonstrated the dominant role of the polar basipetally transported au
xin in AD. The results suggest a mutual interaction between the basipo
lar IAA transport system and cytokinins obviously produced in the root
s and transported via the xylem into the stem of the pea plants.