Storing seeds is one of the main means of ex situ conservation and involves drying as the first step in the preservation process. The priming procedure itself implies frequently the use of stressing agent, as it is the case for PEG and salt. Species in bold may have particular storage challenges, e. This review will highlight those exciting discoveries to update the current status of our understanding of seed dormancy and germination mechanisms. Citation: HortScience horts 50, 6; Ballesteros et al.
Indeed, all germinating seeds found in the field contained bean weevil larvae, indicating that the physical damage facilitated germination. The physiological needs for in vitro germination rates for terrestrial orchids vary among species and response levels can be low, possibly as a result of seed dormancy Rasmussen, It is speculated that accumulation of endogenous osmotica, cell vacuolization, together with cell wall loosening initiated during priming, might determine the embryonic axis extension and radicle protrusion during post-priming germination. Joker, M E. The history of seed vigor testing.
Overall, these studies indicate that about a third of the tested orchid species have seeds that undergo precipitous loses in germinability over relatively short times in dry, cold storage, a response that might relate to the physical transformation of the seed lipids e. However, at least plant species have become extinct in the last 50 years and c. In vitro seed germination in Doritis pulcherrima. Evaluation of seed quality: from physiology to international standardization.
Data for the best combination of warm plus cold stratification for promoting germination are shown in Fig. There is no doubt that the utilization of computers for seed vigor assessment will increase significantly in the future, but seed and seedling imaging analyses are more than promises in seed research by associating seed morphology to its performance or by the use of computerized systems to directly evaluate seed vigor. The evaluation of germination and the identification of seed lots of high performance is an important initiative towards successful crop production, and consequently information from seed laboratories must accurately detect differences in physiological potential among tested seed lots. Adapted from Delouche and Caldwell, However, the general challenges of storing orchid seeds have been reviewed by Pritchard and Seaton and Popova et al. The use, distribution or reproduction in other forums is permitted, provided the original author s or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice.
Metabolism of ROS, mainly H2O2, which is believed to play a central role in oxidative status signaling, is strictly associated to other reactive species and signaling molecules such as nitric oxide and hydrogen sulfide, which contribute and regulate the transition from dormant to germination phase [ , , ]. Acid scarification followed by cold stratification also has been found to break dormancy. In , Lakon proposed the differentiation of high and low vigor seeds based on the location and extent of color as well as appearance of staining and tissue texture. Five groups of seeds were weighed to the nearest 0. The low germination rate has been associated to early signs of membrane disorganization while the occurrence of seedling abnormalities in the final stages of deterioration is attributed to the significant death of tissues in different seed parts, particularly in meristematic tissues.
Species in bold may have particular storage challenges, e. Electrical Conductivity Together with the tetrazolium test, the electrical conductivity EC test is classified as a biochemical test. In addition to the development of research supported by image analysis tools, it has been important develop methods based on the generation or identification of new physiological markers. The above-mentioned results have demonstrated that water transport and sufficient water supply for embryo during post-priming germination regulated by AQPs may be one of the crucial components modulated by pre-sowing seed priming that influences germination rate and stress resistance. Fern spore germination in response to environmental factors. It was found that osmopriming of Brassica napus seeds induced expression of cell division control protein 48 homolog C, cyclin P4;1, cyclin like protein and topoisomerase II in dry seeds, as well as proliferating-cell nuclear antigen 2 and cyclin dependent kinase 3;2 during imbibition [ 36 ].
Germination percentage of seeds of the four cultivars increased with 0- to min soaking time in concentrated H2SO4, but for seeds soaked for 50 min it decreased to the same level as the control Fig. These current accepted concepts do not include the possible persistence of the effects of seed vigor throughout the plant development cycle persisting until yield.
Effect of cold stratification on dormancy break. Some seeds of O. Hasegawa, A. However, the pericarp can pose a physical restraint to germination and so the seeds are extracted and sown directly in pots or in germination beds. Effect of storage temperature on green spore longevity for the ferns Equisetum ramosissimum and Osmunda regalis. One-hundred mature, well-developed seeds of each of the four pomegranate cultivars were selected haphazardly, and their color and shape observed.
Most, if not all, cell cycle proteins responsible for cell cycle control appear to be already present in dry mature seeds, although some of them should be synthesized de novo. Shen, S. Too early to call it a success: an evaluation of the natural regeneration of the endangered Metasequoia glyptostroboides. This means combining fields of ecology with molecular genetics and modelling to understand the role of environmental signalling and developmental processes in generating behavioural variation among and within populations of seeds. Changes in germinability and desiccation-sensitivity of recalcitrant Hopea hainanensis Merr. They suggested testing for germination after exposing seeds to temperatures from 50 oC to oC for relatively short periods to estimate the storability of seed lots.
The seed environment is interesting because it permits a kind of mechanical communication between embryo and endosperm that controls the final balance of the two tissues in the mature seed.
Fabaceae Seeds of Pterocarpus indicus are mm long and weigh mg on average Joker,