ANALYSES OF MUTANTS OF 3 GENES THAT INFLUENCE ROOT HAIR DEVELOPMENT IN ZEA-MAYS (GRAMINEAE) SUGGEST THAT ROOT HAIRS ARE DISPENSABLE

Root hairs are specialized epidermal cells that are thought to play an important role in plant nutrition by facilitating the absorption of w ater and nutrients. Three maize mutants with abnormal root hair morpho logies (rth1, rth2, and rth3) have been isolated from Mutator transpos on stocks. All three root hair mutant phenotypes are controlled by sin gle recessive alleles. The rth1 mutant initiates normal-looking root h air primordia that fail to elongate. The normal-looking root hair prim ordia of the rth2 mutant elongate to only approximately one-fifth to o ne-fourth the length of wild type root hairs. Like rth1 primordia, rth 3 primordia undergo little elongation. However, unlike the relatively normal-looking rth1 primordia, rth3 primordia are distinctly abnormal when viewed through a scanning electron microscope. The rth1 mutant ex hibits pleiotropic nutrient deficiencies, while the rth1 and rth3 muta nts grow vigorously. This finding suggests that under some environment al conditions, root hairs are less important to plant growth than has been previously thought. The rth1, rth2, and rth3 genes have been mapp ed to chromosomes 1L, 5L, and 1S, respectively, via crosses with BA tr anslocation stocks. The rth2 allele exhibits reduced transmission thro ugh the male gametophyte, but a normal rate of transmission through fe male gametophytes; rth1 and rth3 are transmitted at normal rates.