Schematic diagram of cluster root functioning in Hakea laurina (IMAGE)
Caption
Hakea laurina exhibits an exudative burst of acid phosphatase and carboxylates (malate and citrate) and H+ release with low-phosphorus (P) availability, which increases the Al3+ concentration in the soil. Aluminum-activated Malate Transporter 1 in Hakea laurina (HalALMT1) is transcriptionally upregulated in the cortex of mature cluster rootlets, facilitating malate release under low-P conditions. The malate transport activity was further enhanced by exposure to Al3+, which may occur in acidic soil. The activity of acid phosphatase was particularly strong in the apoplast of the cortex. Hakea laurina develops a suberized endodermis, but not a suberized exodermis, in cluster rootlets, which may facilitate malate exudation and acid phosphatase release from the cortex into the rhizosphere.
Credit
Hirotsuna Yamada, Hiroshima University (Adapted from Yamada et al. (2025), New Phytologist, CC BY 4.0)
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