The fruits of watermelon, Citrullus lanatus were collected at different stages of development from plants grown at the bank of river Jamuna, Delhi, to investigate the changes in gibberellins during their progressive maturation. Gibberellin-like substances in fruits were detected at all stages, namely, 5, 7, 9, 11, 1.3, 14, 17, 25 and 35 days after pollination. The activity as bioassayed by d2 mutants of Zea mays was very low 5 days after pollination, but rose to a peak on the 17th day and declined as the fruit matured. The maximum activity was obtained in the fruit when it attained only 40% of its final fresh weight which indicates that the gibberellin-like factors, detected in the present work, may have a role in fruit growth. Chromatography of the acidic fraction of the pulp of mature watermelon fruits using different solvents provides evidence for the presence of at least three gibberellin-like factors.
Primary root-tips of Vicia faba were treated with a 1:9 mixture of 1N HCl and 45% acetic acid at 90° for 1 to 7min after pretreatment with 0.05% colchicine for 3hr, and stained by Feulgen and squashed. Within 2 to 4min treatment the heterochromatic segments in metaphase chromosomes were revealed. Further hydrolysis resulted figures analogous to chromosome fragmentation and loss of stainability from whole regions of chromosomes. The results obtained in the present experiment indicate that this HCl-acetic acid treatment is useful as a method for revealing H segments in metaphase chromosomes. Moreover, this treatment is more favorable and effective than the cold treatment in revealing H segments. It is inferred that H segments revealed in the present experiment represent the difference in the chemical composition of chromosomal nucleoproteins.
The following three types of the population effect were found when pollen grains were cultured on the surface of SAP (sugar-agar plate). (1) Positive population effect: Sitimulation of the growth of the pollen tube in accordance with increasing pollen population (e. g. Lilium longiflorum pollen). (2) Negative population effect: Retardation of the growth of the pollen tube in accordance with decreasing pollen population (e. g., Camellia sasanqua pollen). (3) No population effect: Neither positive nor negative effect is observed (e. g., Camellia japonica pollen). The effect of mixing pollen grains on the growth of the pollen tube was named the “mixture effect” and an inhibitory effect was called the “negagitive effect”. A promoting effect was called the “positive effect”. A strong negative population effect was observed when the pollen grains of Lilium longiflorum, Camellia japonica and Thea sinensis were cultured near the pollen grains of Camellia sasanqua. The growth of the Lilium longiflorum pollen tube was inhibited when its pollen grains were germinated on the SAP where the pollen grains of Camellia sasanqua had been cultured and removed. Hence, it is sugested that a growth inhibitory substance diffused from the pollen frains of Camellia sasanqua into SAP.