Comparison Of Micromorphological Characters In Oryza

The rice genus (Oryza L.) belongs to the subtribe Oryzinae, tribe Oryzeae, subfamily Oryzoideae of the grass family (Poaceae), and contains over 20 wild species and 2 cultivated rice species. Wild rice species have higher tolerance to environmental stresses, many agriculturally excellent characters and important genes, which have not existed in cultivated rice, but play an important role in cultivated rice breeding. In this paper, the morphological features of lemma, leaf phytolith, and leaf lower epidermis, and anatomical structure of leaf and culm were investigated. The results may provide an important reference to use the wild rice germplasm. The major results of the present study are as follows.(1) Comparison of the lemma in Oryza. The 5 kinds of tubercles have been classified based on the characters of tubercles, which were e.g."bi-peak"tubercle kind,"multi-peak"tubercle kind,"simple-peak"tubercle kind,"trace"tubercle kind and"warty-peak"tubercle kind. The 4 kinds of lemma hairs have been classified based on the difference of lemma hairs. The length and epidermal microstructure of awn showed some difference among rice species.(2) Comparison of fan phytolith of leaf in Oryza. Fan phytolith from leaf bulliform cell consists of fan handle, fan circle and fan lateral, and has some measurable indicators:the length of fan handle (a), the length (b) and width (c) of fan circle, and b/a. Fan phytolith was classified as long handle,short handle and intermediate types based on the ratio of b/a. In one species, there was much difference among fan phytolith, all the three types existed, but only one was in the majority.(3) Comparison of leaf lower epidermis in Oryza. Oryza plants showed significantly differences in the following traits: the density and row number of stoma, the area and length/width of long cell, the number and distribution of papillae with different sizes. These traits were valuable for the identifying Oryza species and for assessing systematic relationships in the genus.(4) Comparison of sub-microstructure of leaf lower epidermis in Oryza. Big warty tubercle was the typical feature of lower epidermal long cell, which existed in most of rice species excluding of O. punctata, O. minuta, O. alta, O. latifolia and O. ridleye. The number and location of small papillae in stomatal complexes were particularly different between species.(5) Comparison of the anatomical structures of leaf and culm in Oryza. The two kinds of leaf have been classified based on the characters of middle vein, which were prominent type and horizontal type. The two kinds of culm have been classified based on the thickness of fiber cell wall, which were thick-walled and thin-walled type. Thick-walled type culm was classified into 4 types: embedded type, connective type, prominent type, and interval type. Thin-walled type culm was classified into 3 types: bulgy type, embedded type, and connective type.