CIRAD, UMR RPB, 911 Avenue Agropolis, BP 64501, F-34398 Montpellier, France.
Tree Physiol. 2013 Jun;33(6):640-53. doi: 10.1093/treephys/tpt034. Epub 2013 May 31.
In Coffea arabica L., the development of direct sowing of somatic embryos (SE) in planting substrate, with subsequent nursery production of plants, has promoted the industrialization of somatic embryogenesis. However, plant conversion rates are still low and require improvements to enhance the cost-effectiveness of commercial micropropagation. With the aim of improving plant regeneration from SE, we studied the morphological and histological criteria and water characteristics during germination and plant conversion of zygotic embryos (ZE) and SE. At the cotyledonary stage, SE produced in a 1 l RITA(®) temporary immersion bioreactor (area 55.8 cm(2)) were morphologically similar in size (2-3 mm) but abnormal as compared with mature ZE. Protein and starch reserve levels were extremely low throughout germination and conversion to plantlets, while the water status remained steady [water content (WC) from 76 to 87%, Ψ from -0.37 to -0.47 MPa, pressure potential from 0.69 to 0.24 MPa]. In ZE, spectacular hydration occurred during the first 3 weeks (WC from 37 to 75%; Ψ from -6.24 to -1.0 MPa). Cotyledons remained undifferentiated for 10 weeks after sowing. Conversely, after only 3 weeks under germination conditions in a RITA(®) bioreactor, spongy and palisade parenchyma and stomata formed in SE cotyledons. The ZE plant conversion was faster than that of SE (14 vs. 22 weeks) and more efficient (rates 96 vs. 55%), with much more substantial hypocotyl and cotyledon development. The use of a new 5 l MATIS(®) bioreactor (area 355 cm(2)), designed especially to favor embryo dispersion and light transmittance to SE, markedly improved the embryo-to-plantlet conversion rate (91%). These results highlight the morphological heterogeneity and lack of protein reserves in SE at the beginning of the germination phase and marked differences in water characteristics. However, they also reveal high phenotypic plasticity, leading to a highly efficient plantlet conversion rate due to better embryo dispersion and light transmittance in more horizontal bioreactors.
在阿拉伯咖啡（Coffea arabica L.）中，通过将体细胞胚直接播种在种植基质中，随后在苗圃中生产植物，促进了体细胞胚胎发生的工业化。然而，植物转化率仍然较低，需要改进以提高商业微繁殖的成本效益。为了提高体细胞胚的植物再生率，我们研究了形态学和组织学标准以及在发芽和植物转化过程中体细胞胚（ZE）和体细胞胚（SE）的水分特性。在子叶阶段，在 1 l RITA（®）临时浸没生物反应器（面积 55.8 cm（2））中产生的 SE 在大小（2-3 mm）上形态相似，但与成熟 ZE 相比异常。在整个发芽和转化为植物的过程中，蛋白质和淀粉储备水平极低，而水分状态保持稳定[含水量（WC）为 76%至 87%，Ψ为-0.37 至-0.47 MPa，压力势为 0.69 至 0.24 MPa]。在 ZE 中，在最初的 3 周内发生了壮观的水合作用（WC 从 37%至 75%；Ψ从-6.24 至-1.0 MPa）。播种后 10 周内子叶仍未分化。相反，在 RITA（®）生物反应器中的发芽条件下仅 3 周后，SE 子叶中形成了海绵状和栅栏状薄壁组织和气孔。ZE 的植物转化率比 SE 快（14 比 22 周），效率更高（转化率分别为 96%和 55%），下胚轴和子叶的发育更为显著。使用新的 5 l MATIS（®）生物反应器（面积 355 cm（2）），该生物反应器专门设计用于促进胚胎分散和 SE 的光透射率，显著提高了胚胎到植物的转化率（91%）。这些结果突出了 SE 在发芽阶段开始时的形态异质性和缺乏蛋白质储备以及在水分特性方面的显著差异。然而，它们也揭示了高表型可塑性，由于在更水平的生物反应器中更好的胚胎分散和光透射率，导致植物转化率非常高。
