Development and Matured Structure Variation of Ovule from Autotetraploid of <i>Robinia pseudoacacia</i>

Abstract

To explore why seed germination rate is very low for autotetraploid of Robinia pseudoacacia (ARP), the developmental process and matured structure of its ovule were studied by paraffin section and structure anatomy in this paper. Ovule development and abortion of ARP can be formally divided into 3 stages. The initial stage occurred from 5th to 30th day after coronal opened up wholly; in this stage, zygotes were dormant, weight and transverse diameter of ovule increased slower, the rate of ovule with embryo was 0%, and the average abortion rate of ovule was 51.9%. The middle stage went through from 30th to 50th day after coronal opened up wholly; during this stage spherical embryo and heart-shaped embryo were observed, embryo and endosperm grew fast, weight of ovule increased rapidly, aborted ovules had yellow-transparent liquid around them, the rate of ovule with embryo was 33.2%, and the average abortion rate of ovule was 30.2%. The later stage came up from 50th day after coronal opened up wholly to ovule maturation, during this stage cotyledonary embryo formed gradually, the average rate of ovule with embryo was 70.8%, and the average abortion rate of ovule was 72.6%. The percentage of three parts (embryo, endosperm and integument) of ARP matured ovule varied obviously compared with matured ovule of diploid Robinia pseudoacacia, for which ARP matured ovules aborted severely. Therefore, the abortion of ARP ovules was the direct reasons why its seeds aborted.