UNEQUAL GROWTH-RATE OF POLLEN TUBES FROM NORMAL AND STRINGLESS PEA GENOTYPES

There was no difference in percentage in vitro germination of pollen from stringless pea (Pisum sativum L.) cv. Sugar Daddy and stringy 'Oregon Sugarpod II' (OSP) and 'OSU 705' (705). However, pollen tubes of 'Sugar Daddy' grew more slowly in vitro than those of OSP or 705. Differences in pollen tube growth rate were demonstrated in vivo following time-course pollinations involving reciprocal crosses of 'Sugar Daddy' with OSP and 705, along with the selfed parents. After 8 hours, pollen tubes from stringless peas ("stringless" pollen) had entered 13% of the ovules compared with 51% for those from stringy peas ("stringy" pollen). Stringless pollen tubes entered 29% and stringy pollen tubes 66% of the ovules after 10 hours. The slower growth of stringless compared with stringy pollen tubes is a plausible explanation for previously observed deficiencies of stringless plants in segregating populations.