1. It is found in protoxylem and first metaxylem tracheids and vessels.

2. The primitive exarch and diarch haplostele with cross-like metaxylem exists in the lower part of CNZ.

3. Exarch Denoting a stele in which the metaxylem develops to the inside of the protoxylem.

4. Basipetal differentiation is seen in the formation of proto-and metaxylem in the stem.

5. The result showed that the maize with high tolerance to drought had fewer cortex cell layer numbers, lesser diameter of metaxylem vessel, more metaxylem vessel amount in primary radicel, an...