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Potassium starvation affects biomass partitioning and sink-source responses in three sweet potato genotypes with contrasting potassium-use efficiencies
Abstract. Rooted single sweet potato (Ipomoea batatas L.) leaves produce and translocate photosynthates, thus representing an ideal model for characterizing the source–sink relationships and responses to various environments. A hydroponics culture study was conducted using rooted single sweet potato leaves to determine interspecific variation in growth, biomass partitioning, and the associated physiological changes among three genotypes Ji22 (low K-use efficiency), Nan88 (high K-uptake efficiency) and Xu28 (high K-use efficiency) in response to variable K supply. Potassium deficiency suppressed biomass accumulation in blades, petioles and roots in all three genotypes, and there was a significantly shorter root length of K-deficient than sufficient roots in all genotypes with diameter (Φ)<0.25 mm and 0.25≤Φ<0.5 mm, but the difference was proportionally larger in K-inefficient genotype Ji22 compared with the other two genotypes. K starvation also severely inhabited the blade net photosynthesis (PN) in Nan88 and Ji22 as well restrained photosynthate translocation, increased starch, hexose and sucrose concentrations and decreased K concentration in blades. The different sweet potato genotypes showed varied photosynthesis-related responses to the K deficiency. Xu28 had greater blade K concentration and net photosynthesis as well as stable of the maximum quantum yield of photosystem II (Fv/Fm, with Fv=Fm-F0) under K deficient, possibly because of a better source–sink balance and more efficient translocation of photosynthates to roots and K to blade, in comparison with genotypes Ji22 and Nan88. Impaired phloem loading during K deficiency was associated with a decline in photosynthetic rate and decreased carbohydrate supply from blades, resulting in restricted root growth.
CP17328 Accepted 27 February 2018
© CSIRO 2018