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.