Characterization of the natural chemical and osmotic environment of early wheat embryogenesis

Abstract

Soluble carbohydrates, amino acids, and major inorganic ions were quantified and compared with the total osmolarity of the ovule. Most of the analyzed components increased rapidly in concentration, reaching a peak at 1 day post anthesis (DPA) and decreasing quickly 1 day later. Within this time period, the osmolarity decreased from 1.49 to 1.18 MPa. The osmolarity then increased to 1.39 MPa at 4 DPA, and yet the overall concentration of analyzed molecules decreased. At 1 DPA, inorganic ions were observed at levels that could produce a high osmolarity (1.11 MPa), followed by the carbohydrates (0.37 MPa) and amino acids (0.07 MPa). Maltose was detected in ovules only from 0 to 2 DPA. Inositol was abundant in the ovules on the day of anthesis, but decreased to non‐detectable levels after 4 DPA. This suggested that ovules allow the rapid entry of solutes into the syncytial endosperm after fertilization, but are osmotically buffered through the increase and decrease of partly identified substances. Specific gravity tests on the liquid squeezed from young endosperm sukpported this new hypothesis. Osmolarity in ovules seems only indirectly related to morphogenetic regulation mechanisms, and it may play a lesser role than the fluctuations of certain specific substances. The observed chemical changes offer insights into the rapidly varying nutritional needs of proembryos. Thus, in this research yielded a useful complex amino acid formula, derived from knowledge of the natural environment of the proembryo, and also an improved proembryo and ovule culture medium.

Toward a property/function relationship for metallothioneins: Histidine coordination and unusual cluster composition in a zinc‐metallothionein from plants

“…Although generally a decrease in complex stability is expected upon increasing the ionic strength, the extent of destabilization in E C is much larger than, e.g., in cyanobacterial SmtA (in which K = 7.9 × 10 11 M −1 has been measured under identical conditions40). Since physiological ionic strengths tend to be even higher than those employed in our study (the osmolarity in developing seeds has been estimated to be as high as 500–600 mM;41 and the pH was measured to be as low as 6.2), the dramatically lowered zinc affinity of E C at moderate ionic strength (105 mM) is remarkable and likely to have functional significance.…”

Improving cotton embryo culture by simulating in ovulo nutrient and hormone levels

“…3), it is likely that much younger proembryos, possibly even zygotes, might also develop normally using the media and procedures described herein. In like manner, novel media formulations and procedures for culturing proembryos of monocotyledonous and gymnospermous species might also be developed from published findings, which list in similar detail nutrient and hormone levels in wheat ovules (Hess and Carman 1993;Carman 1995;Carman et al 1996;Maës et al 1999;Hess et al 2002;Carman and Bishop 2004) and Douglas fir megagametophytes (Carman et al 2005). Such media and procedures may be useful when conducting zygotic or somatic embryogenesis-based transformation procedures.…”

“…The value of using multiple amino acids to culture small explants such as meristems is well documented (Carman 1995), and formulations containing multiple amino acids were considered responsible for achieving rapid growth from cultured proembryos of barley (Norstog and Smith 1963), Datura tatula L. (devil's trumpet: Matsubara 1964), rice (Zhao et al 1999), and wheat (Carman 1995;Maës et al 1999). Our GOS1 formulation also differed from MS medium by containing 8.2-fold more P, 2.4-fold more K, 2.7-fold more Ca, 5.1-fold more S, 8.8-fold more myoinositol, and arabinose, melibiose, malic acid, citric acid, a variety of amino acids, and mannitol (as an osmoticum, −1.10 MPa), none of which are in MS medium.…”