I. Chromosome studies

1. Duration of different stages of meiosis in pollen mother cells of rice

Ting-Bi Zhang and Huan Zhu

Genetics Lab., Biology Department, Wuhan University, Wuchang, Hubei, China

To determine the duration of successive stages of meiosis, young panicles of cultivar Guanglai 4 were sampled and fixed at two-hour intervals for a day, in August at Wuchang. The duration of a stage (Si) was estimated by the frequency of cells at the stage as follows:

                             No. of cells at stage i
                    Si=T X  _______________________,
                             Total cells  in  meiosis
where T is the duration of meiosis. It was estimated to be 31 hours on the basis of increase of auricle distance as compared with the beginning and end of meiosis at a certain position of the panicle.

The results are shown in Table 1. The leptotene stage had a long duration exceeding 16 hours, followed by the pachytene stage of 5 hours. The shortest was 19 minutes for anaphase I.

The data also showed that cells in different spikelets and in different anthers of the same spikelets are not synchronized in initiating meiosis, hence different stages were observed in the material fixed at each hour, but cells neighboring in the same anther were synchronized.

Table 1. Pollen mother cells at different meiotic stages in 
         samples fixed at different hours
_______________________________________________________________
            AM                PM                 Total    Dura-
Stage                                             no.     tion

             1  3  5  7  9 11  1  3  5  7  9 11           h   m
_______________________________________________________________
Leptotene   21 23 26 19 21 17 23 23 23 17 21 17   251    16  05
Pachytene    5  7  4 11  5  9  9  5  5  7  4  7    78     5  00
Diplotene    1     1     2        1        1        6        23
Diakinesis   2  4  3  4  3  2  2  3  1  2  4  2    32     2  03
Metaphase I  6  2  4  2  3  5  5  2  4  5  1  1    40     2  34
Anaphase I      1     1     2           1           5        19
Telophase I  2     1     1     1  2                 7        27
Prophase II     1  2  1  1  3  3  4        1       20     1  17
Metaphase II 4  3  1  2  1  2  3  4  2  2  2  1    25     1  36
Anaphase II  1     2  3     1     2     1          10        38
Telophase II 1     3  2  1     1  1        1       10        38
_______________________________________________________________
Total       43 41 47 45 38 41 47 47 35 37 35 28   484    31  00
_______________________________________________________________