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Occurrence of potassium location in oil palm tissues with reserve sugars: consequences for oil palm K status determination

Lamade E., Ollivier J., Rozier-Abouab T., Gérardeaux E.. 2014. In : IOPRI. 4th International Oil Palm Conference, Bali, Indonesia, 17-19 June 2014. s.l. : s.n., 16 p.. International Oil Palm Conference. 4, 2014-06-17/2014-06-19, Bali (Indonésie).

In some fertilizer trials for oil palm, it is observed that potassium leaf content was not in concordance with potassium application. In some cases no "leaf" response is observed (leaflet potassium content from leaf rank 17 according to specific LD IRHO method) whatever the K level. Agronomists have suggested to look for potassium content in others organs like rachis, showing best adjustment between K content, yield and K application; This K content difference between rachis and leaflets may be related to their different metabolic role for the plant; When leaflets are devoted to photosynthetic acquisition of carbon for the whole plant, rachis play obviously a role in photosynthetic product transportation; Potassium is often mentioned as involved in sugars translocation. In order to explain K content variations within organs, an experimental observations design has been elaborated on a factorial fertilizer trial (ALCP 10, factorial K4 x Ca2 in North Sumatra) involving precise samplings on vegetative organs as leaflets petioles, rachis, trunk and roots as well as fruits, spikelets and bunch stalk. Both mineral content analyses and sugars content (soluble sugars and starch) were performed on a total of 36 oil palm trees belonging to two different contrasting genetic materials. For strengthening our hypotheses, two other set of data were overviewed for K and sugars locations; The first one is a complete dissection of a crown from very young bud leaf stage until old leaves, the second is an exploration of sugars reserves in the crown in North Sumatra conditions. Maximal K mineral content was observed in trunk bottom (for all planting material and treatment) when soluble sugars are high and starch low. Generally it has been observed that potassium is high in petiole of very young leaves (1 to 3) and increasing in bunch rachis until fruit maturation. Leaflets of young leaves (rank -2) contain more potassium that leaflets at rank 17 due to their high proportion in reserve sugars before starting strong photosynthetic activity. Hypothesis is merging from a high co-occurrence of K with soluble sugars in oil palm (most probably glucose) which are involved in the reserve mobilization to elaborate not only bunches but also new young leaves. An inverse relation is found between K concentration and starch.. It seems that equilibrium between starch and soluble sugars content at organs scale and the K level are a key to elaborate a clear K nutrient status for oil palm.

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