Germination and Seedling Development of Soybeans in a Carbon Dioxide‐deficient Atmosphere

Abstract

During the initial phase of germination and seedling development of soybeans, most of the increase in dry weight in the embryo axis occurred in the hypocotyl. The epicotyl did not undergo a rapid increase in size and dry weight until the 4th to 5th day of growth. From day 1 to 11 dry weights of the hypocotyls in the “CO2‐normal” and “CO2‐Iimiting” (less than 50 ppm [0.005%] atmospheric CO2) treatments were similar. By day 13 the CO2‐normal hypocotyls had continued their rapid increase in dry weight while the dry weight of the hypocotyls grown under CO2‐limiting conditions had decreased. The parallel decrease in dry weight of the cotyledons that occurred for both CO2 treatments (days 1 to 13) suggested that CO2 content of the atmosphere is not a controlling factor in the digestion or hydrolysis of food reserves in the cotyledon during germination and seedling development. This is supported by the failure of the CO2 treatments to produce significantly different patterns in utilization of lipids, total carbohydrates, or proteins in the cotyledons. The seedlings grown under either the limiting or normal CO2 atmospheres utilized their cotyledonary carbohydrates and lipids before the proteins. Sufficient food reserves are present in the soybean cotyledon storage cells for seedling development until about day 9. Net CO2 uptake by soybeans in a CO2‐normal environment first occurred between days 9 to 11.

Incorporation of crop phenology in Simple Biosphere Model (SiBcrop) to improve land-atmosphere carbon exchanges from croplands

“…The initial biomass values at emergence (Green and Sudia, 1969;Blum et al, 1980;Smiciklas et al, 1992;Richardson and Bacon, 1993;Pinhero and Fletcher, 1994;Hameed et al, 2003) were set considering the average planting density based on the plant and row spacing typical for each crop. Starting from the day of emergence, a daily LAI value was estimated based on leaf carbon (details follow), for deriving fPAR and estimating sub hourly photosynthetic assimilate, respiratory carbon (i.e.…”

Partição da atividade da redutase do nitrato durante o desenvolvimento de plântulas de soja (>i<Glycine max>/i< L. Merr)

“…Estes desempenham um importante papel, pois sao os sítios de acumu lação das duas principais reservas, lipÍdeos e proteínas, que durante a germinação são hidrolizados e translocados para o ápice embriônico em desenvolvimento (GREEN e SUDIA, 1969).…”

“…6.4. Efeito da remoçao dos cotilédones na atividade da en zima redutase do nitrato e no desenvolvimento das plântulas Os cotilédones de soja contêm o material de re serva das sementes, que durante a germinação são hidrolizados e translocados para o ápice em desenvolvimento (GREEN e SUDIA, 1969).…”