The evolutionary context of root epidermis cell patterning in grasses (Poaceae)

Figures & data

Figure 1. Root epidermis patterning in plants. (A) Type 1 in which any root epidermal cell may produce a root hair, (B) Type II in which only the shorter cells produce root hairs, (C) Type III with a striped pattern in which files of root hairs and non-root hair cells are present. (D-E) Two possibilities for the presence of the alternative pattern of shorter and longer cells—(D) the asymmetric shootward-last division or (E) the asymmetric expansion of identical daughter cells after the symmetrical division.

Figure 2. Phylogeny of Poaceae from the Catalogue of New World Grasses. Blue indicates subfamilies in which symmetric shootward-last divisions was present, red indicates asymmetric shootward-last divisions, subfamilies that were not investigated are marked with white, the number of analyzed species can be find in brackets.

Table 1. Species of the Poaceae family with a known root epidermis pattern

Subfamily	Species	Type	Description	Refs.
Bambusoideae	Pleioblastus chino Max	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
Chloridoideae	Sporobolus cryptandrus Torr.	Type B	Symmetric last division, some epidermal cells produce root hairs	20
	Chloris gayana Kth.	Type A/B	Slightly asymmetric division, mainly shorter cells produce root hair	20
Ehrhartoideae	Oryza sativa L.	Symmetric	Symmetric shootward-last cell division, however after root hair initiation atrichoblasts elongate more than trichoblasts.	10
Pooideae	Agrostis alba L.,	Type A/ festucoid	Asymmetric last division, only shorter cells produce root hairs	21
	A. tenuis Sibth.	Type A/ festucoid	Asymmetric last division, only shorter cells produce root hairs	21
	Anisantha sterilis L.	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
	Avena sativa L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	Beckmannia syzigachne Steud.	Type A/ festucoid	Asymmetric last division, only shorter cells produce root hairs	21
	Brachypodium sylvaticum L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	B. distachyon L.	Asymmetric	Asymmetric shootward-last division, only shorter cells produce root hairs	10
	Elytrigia repens L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	Festuca rubra L.	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
	Holcus lanatus L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	Hordeum vulgare L,	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	Hordeum vulgare L.	Symmetric division	Symmetrical shootward-last division, asymmetrical expansion, only shorter, rootward cells produce root hairs	15
	Phalaris arundinacea L.	Type A / Vd	Asymmetric last division, only shorter rootward cells produce root hairs	21, 24, 25
	Phleum pretense L.	Type A / festucoid / Vd	Asymmetric last division, only shorter rootward cells produce root hairs	20, 21, 25
	Poa trivialis L.	Type A	Asymmetric last division, only shorter cells produce root hairs	20
	P. pratensis L.	Type A/ festucoid	Asymmetric last division, only shorter cells produce root hairs	21
	P. annua L.	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
	Secale cereal L.	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
	S. cereal x Triticum monoccocum	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	S. cereal x T. aestivum	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
	T. monococcum L.	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
	T. aestivum L.	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
Panicoideae	Panicum capillare L.	Type B/ panicoid	Symmetric last division, some epidermal cells produce root hairs	21
	Digitaria sanguinalis L.	Type B/ panicoid	Symmetric last division, some epidermal cells produce root hairs	21
	Miscanthus sinensis A.	Type B/ panicoid	Symmetric last division, some epidermal cells produce root hairs	21
	M. sinensis L.	Vd	Asymmetric shootward-last division, only shorter rootward cells produce root hairs	25
	Andropogon scoparius Michx.	Type B/ panicoid	Symmetric last division, some epidermal cells produce root hairs	21
	Panicum miliaceum L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	P. capillare L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	Zea mays L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25
	Saccharum officinarum L.	N	No evident trichoblasts, symmetric shootward-last division, any cell can produce root hairs	25

A description is given in the text; Vp—trichoblasts in vertical patterns and derived from the proximal sister cell; Vd—trichoblasts in vertical patterns and derived from the distal sister cell; N—no evident trichoblasts).

Figure 3. The proposed types of root epidermis patterning in plants. Description is given in the text.