| Fiber growth on cultured ovules is initiated by phytohormone and inhibited by the absence of atmospheric CO2. Variation in response of ovules to culture was observed by Beasley. In this study we examined the differential response of ovules to culture and to CO2 among 15 cotton Gossypium hirsutum L. genotypes. Unfertilized ovules were cultured at 30 C for 14d in an elevated CO2 atmosphere, with sister ovules from the same ovary cultured in ambient CO2 as controls. The response of ovules to culture was greatly influenced by genotype, CO2, and year or environment. There were significant genotypic differences in the responses to culture and to CO2 between years. In 1987, ovules from field plants of half of the genotypes cultured on BTN medium tended to produce callus in ambient CO2, while these ovules showed normal fiber development in 5% CO2; the differential response of genotypes to culture was diminished by enriched CO2. The number of fibered ovules was increased by CO2, as percentage of the control, from 0 to 227% depending on genotype. The low percentage increases resulted because some genotypes grew well in ambient CO2. In 1988, 6 genotypes were selected as representative of the range of responses to culture (normal ovule or fiber growth, intermediate, and only callus or few fibers in ambient CO2). Ovules from greenhouse plants of the 6 genotypes cultured on BT medium all grew normal fibers with or without enriched-CO2 except GSC 25, whose ovules produced only callus in ambient atmosphere. GSC 25 ovules tended to brown and die when cultured in ambient CO2, but remained white and expanded in 5% CO2 when cultured on BT medium without exogenous hormones; with the addition of 5 uM of IAA alone the ovules produced callus in ambient CO2 but grew normal fibers in 5% CO2 enrichment. When ovules from field plants of the 6 genotypes were cultured at the end of growing season (Oct. 11) , they grew callus or few fibers in ambient CO2 while producing normal fiber in CO2 enrichment; the CO2 effect on fiber growth was markedly increased. Therefore, both culture medium and parental plants altered the response to culture and to CO2. BT medium and greenhouse plants supported better fiber growth in ambient atmosphere. The environment in which the parental plants were growing apparently shifted the response of the ovules to culture. The results indicate that CO2 conditionally affects the response of ovules to culture, i.e., when ovules grow normally the CO2 effect is minimal; when ovules grow abnormally, CO2can prevent callusing and promote normal ovule and fiber growth. CO2 could moderate adverse conditions for normal fiber development on ovules subjected to certain stresses, although the external factors and the mechanism of CO2 action in buffering against the stresses are unclear. The phytohormones are known to play a key role in fiber development in vitro. The results show that CO2 promotes normal ovule and fiber development. It may interact with phytohormones in this respect, but further study is needed to determine its exact function. |
https://www.cotton.org/beltwide/proceedings/8395/abstracts/2219.cfm
No comments:
Post a Comment