J Syst Evol ›› 1996, Vol. 34 ›› Issue (2): 142-151.

• Research Articles • Previous Articles     Next Articles

On Phylogeny of the Taxaceae from Morphology of Seedlings

Ye Neng‐gan, Liao Hai‐min, Li Shu‐jiu   

  • Published:1996-03-18

Abstract: This paper deals with the morphology of seedlings of the Taxaceae in China.Our morphological and anatomical investigations reaved that the cross morphology of seedlings and the structure of the cotyledons can be used to explain the phylogeny of the Taxaceae, and the seedlings of the Taxaceae can be classified into three types.In Type I,represented by only Torreya, seedlings strong, hypogeal; hypocotyl very short;cotyledon thick and fleshy, with some stomata on the upper epidermis which is protective tissue,but with no stomata on the lower epidermis,which absorbes nutrient from endosperm;mesophyll has not differentiated into palisade and spongy parenchyma,and with abundant starch grains in its cells;two vascular bundles lie side by side in the upper part or at the top of the cotyledon,but fuse into one in the lower part of the cotyledon,and a resin canal present on the side of phloem. In Type II,represented only by Amentotaxus,seedling strong,epigeal; hypocotyl elongated and thickened in the lower part;cotyledon somewhat fleshy,with some stomata on the upper epidermis but no on the lower epidermis;mesophyll not differentiated into palisade and spongy parenchyma;plastid greenish, but accumulated starch mainly;vascular bundle single,wide and flat,but it tends to divide into two near the tip of the cotyledon resin canal absent. In Type III, represened by Taxus,Pseudotaxus,and probably,seedling thin,epigeal; hypocotyl elongated,slender(somewhat thick in the lower part inAustrotaxus only);cotyledon thin,leaf-1ike,Without stomata on the upper epidermis,but with stomata arranged in line,forming stoma band on the lower epidermis;mesophyll differentiated into palisade and spongy parenchyma and functions like a true leaf; vascular bundle single,narrow;resin canal absent. These three types represent a phylogenetlcal sequence from primitive to advanced.

Key words: Morphological and anatomical character, seedling, Taxaceae, Phylogeny