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Removing Potassium-deficient Leaves Accelerates Rate of Decline in Phoenix roebelenii O'Brien

1994; American Society for Horticultural Science; Volume: 29; Issue: 7 Linguagem: Inglês

10.21273/hortsci.29.7.823

2327-9834

Timothy K. Broschat,

Banana Cultivation and Research

Palm K status and No. leaves Potassium deficiency is a widespread and often serious disorder on many species of palms throughout the world (Chase and Broschat, 1991). Early symptoms usually include translucent yellow, orange, or necrotic spotting of the oldest leaves. This is usually accompanied by marginal necrosis on leaves or leaflets that eventually gives the oldest leaves a gray frizzled appearance (Broschat, 1990; Chase and Broschat, 1991). Potassium is mobile within plants, and deficiency symptoms are most severe on the oldest leaves, becoming less severe on younger leaves (Mengel and Kirkby, 1982). As the K deficiency becomes more severe, the symptoms will affect progressively younger palm leaves until no symptom-free leaves remain. At this point, if not treated, new leaves will emerge chlorotic. They will be reduced in size and have extensive necrosis. Death of the palm’s only shoot meristem often follows (Broschat, 1990). Leaves normally remain on a healthy palm for 2 or more years, depending on the species, and each palm will retain a species-specific number of leaves (Tomlinson, 1990). Mildly K-deficient leaves are typically removed during landscape maintenance because they are visibly discolored; severely deficient leaves appear dead except for the rachis and adjacent areas of the leaflets. Under conditions of K deficiency, K from the oldest leaves is mobilized for use by the newly expanding leaves. Premature removal of the oldest K-deficient leaves may remove a K source needed for plant growth. Potassium required for continued growth may be mobilized from the oldest remaining leaves that previously may have been symptom-free. As these leaves become symptomatic and are subsequently removed, still younger leaves may be used as a source of K by the meristem. Thus, removal of Kdeficient leaves may accelerate the rate of