Abstract
‘Tonda gentile delle Langhe’ hazelnut bloomed from 22 Dec. to 19 Jan. Fertilization occurred about 5 months later, in the last 10 days of May. In the first days of June, the embryo was globular whereas the free nuclear endosperm had started to become cellular. Around the middle of June the embryo was heart-shaped and the endosperm was entirely cellular. In the following 2 weeks, the endosperm became vacuolated and then disintegrated. Cotyledons formed (torpedo stage) and grew quickly, filling the ovule by the end of June. The seed had its final shape and dimension by 20 July, but the embryonal axis continued elongating until nut maturity, 15 to 30 Aug. Mature embryos contained six to eight leaf primordia, the apical meristem, and the radicle.
fertilization of the embryo and endosperm, but no viable seed is produced as a result of embryo abortion during development ( Stout, 1936 ). The resultant berry contains a “seed trace,” or underdeveloped ovule of varying size, which may or may not have an
for the seeds to germinate with conventional methods. Low-viability seeds also occur either when the embryos come from early-maturing fruits where seeds do not reach the mature stage or when the embryos come from stenospermic seedless fruits such as in
become the embryo (kernel) containing the cotyledons and the axis. Cotyledons are the edible nut meat. Pistachio nut growth has three stages: 1) hull and shell expansion that produces the final in-shell nut size; 2) thickening and hardening of the
traditional breeding methods because of cross-incompatibility, embryo dysplasia, dormancy, scanty germination rates, and low efficiency propagation ( Cheng, 2007 ). However, tissue culture seems to be an attractive tool for overcoming these bottlenecks for
continue to be useful in the future ( Liu et al., 2014 ). However, embryo abortion is a common phenomenon in jujube that prevents the formation of viable seeds and restricts cross-breeding efficiency; therefore, obtaining hybrid progeny remains a major
Embryo rescue (ER), or the excision and culturing of immature zygotic embryos from developing seeds, is conducted under aseptic conditions to obtain viable and pathogen-free plantlets ( Bhojwani and Razdan, 1986 ; Morel, 1960 ). The technique was
low germination rate and long germination time. It usually takes 2–3 years to overcome the double dormancy of the hard, impermeable seedcoat and immature embryos ( Dirr and Heuser, 2006 ; Hu et al., 1979 ). Pretreatment at room temperature for 2
Techniques are described to determine whether embryos are formed in ovules of incompatible crosses between Ornithogalum (L.) plants, and to rescue embryos in cases where the development of embryos is halted following fertilization. By using Herr's clearing liquid, it can be ascertained within 5 hours whether hybrid embryos have been formed. Such embryos can be rescued by culturing them in ovulo on basal medium containing 70 g sucrose/liter and no added growth regulators. The embryos' requirement for sucrose changes as they develop; therefore, cultured ovules are transferred after 14 days to a medium containing 10 g sucrose/liter, where germination occurs.
impermeability may be due to multiple layers of tightly spaced, thick-walled cells in the pericarp and testa, the presence of waxes, lignins, and pectins, or a combination of these factors. Seeds with physiological dormancy possess embryos that cannot generate