Figure 3.

NH₄⁺ Deprivation Restored cap1-1 Root Hair Growth and Tip-Focused Ca²⁺ Gradient.

(A) The absence of NH₄⁺, but not NO₃⁻, restored root hair growth in cap1-1. Seedlings of the wild type and cap1-1 grown for 7 d on MS, MS lacking NH₄⁺ (MS-NH₄⁺), and MS lacking NO₃⁻ (MS-NO₃⁻). Root hairs of cap1-1 were only restored in NH₄⁺-free medium.

(B) Comparison of root hair lengths and numbers between the wild type and cap1-1 on MS, MS-NH₄⁺, and MS-NO₃⁻ media. Data were collected from seedlings grown on MS (n = 100), NH₄⁺-free (n = 90), and NO₃⁻ deprivation (n = 60) media from three separate experiments as described in Figure 1B. Error bars represent means ± se.

(C) The tip-focused Ca²⁺ gradient was reestablished in YC3.6-transformed cap1-1 on NH₄⁺-free but not on NO₃⁻ deprivation media. The [Ca²⁺]_cyt of root hairs was measured as described in Figure 2A (a, initiation phase; b, transition phase; and c, tip growth phase). Bars = 10 µm.