Agrocampus-Ouest, UMR 1345 IRHS, SFR QUASAV, 16 Boulevard Lavoisier, 49045 Angers, France.
Université Angers, SFR QUASAV, 42, rue Georges Morel, BP 60057, 49071 Beaucouzé cedex, France.
Plant Sci. 2014 Mar;217-218:18-26. doi: 10.1016/j.plantsci.2013.12.001. Epub 2013 Dec 8.
Hypocotyl growth is a key characteristic for plant emergence, influenced by environmental conditions, particularly temperature, and varying among genotypes. Cellular changes in Medicago truncatula hypocotyl were characterized to study the impact of the environment on heterotrophic growth and analyze differences between genotypes. The number and length of epidermal cells, ploidy levels, and sugar contents were measured in hypocotyls grown in the dark at 20 °C and 10 °C using two genotypes with contrasting maximum hypocotyl length. Hypocotyl elongation in the dark was due to cell elongation and not to an increase in cell number. A marked increase in cell ploidy level was observed just after germination and until mid elongation of the hypocotyl under all treatments. Larger ploidy levels were also observed in the genotype with the shorter hypocotyl and in cold conditions, but they were associated with larger cells. The increase in ploidy level and in cell volume was concomitant with a marked increase in glucose and fructose contents in the hypocotyl. Finally, differences in hypocotyl length were mainly due to different number of epidermal cells in the seed embryo, shown as a key characteristic of genotypic differences, whereas temperature during hypocotyl growth affected cell volume.
下胚轴生长是植物出芽的一个关键特征，受环境条件影响，尤其是温度，并在不同基因型之间存在差异。为了研究环境对异养生长的影响，并分析基因型之间的差异，我们对蒺藜苜蓿下胚轴的细胞变化进行了研究。使用两个最大下胚轴长度存在显著差异的基因型，在黑暗中于 20°C 和 10°C 条件下测量下胚轴中表皮细胞的数量和长度、倍性水平和糖含量。黑暗中下胚轴的伸长是由于细胞伸长而不是细胞数量的增加。在所有处理条件下，在下胚轴伸长初期和中期观察到细胞倍性水平显著增加。在所有处理条件下，在萌发后和下胚轴伸长中期，细胞倍性水平都显著增加。在较短下胚轴和低温条件下，也观察到较大的倍性水平，但它们与较大的细胞有关。倍性水平和细胞体积的增加伴随着下胚轴中葡萄糖和果糖含量的显著增加。最后，下胚轴长度的差异主要是由于种子胚中表皮细胞数量的不同，这是基因型差异的一个关键特征，而在下胚轴生长期间的温度影响细胞体积。
