Université Montpellier 2, UMR AMAP, Montpellier, France; CNRS, UMR AMAP, Montpellier, France.
PLoS One. 2013 Sep 4;8(9):e74727. doi: 10.1371/journal.pone.0074727. eCollection 2013.
Domestication can influence many functional traits in plants, from overall life-history and growth form to wood density and cell wall ultrastructure. Such changes can increase fitness of the domesticate in agricultural environments but may negatively affect survival in the wild. We studied effects of domestication on stem biomechanics in manioc by comparing domesticated and ancestral wild taxa from two different regions of greater Amazonia. We compared mechanical properties, tissue organisation and wood characteristics including microfibril angles in both wild and domesticated plants, each growing in two different habitats (forest or savannah) and varying in growth form (shrub or liana). Wild taxa grew as shrubs in open savannah but as lianas in overgrown and forested habitats. Growth form plasticity was retained in domesticated manioc. However, stems of the domesticate showed brittle failure. Wild plants differed in mechanical architecture between shrub and liana phenotypes, a difference that diminished between shrubs and lianas of the domesticate. Stems of wild plants were generally stiffer, failed at higher bending stresses and were less prone to brittle fracture compared with shrub and liana phenotypes of the domesticate. Biomechanical differences between stems of wild and domesticated plants were mainly due to changes in wood density and cellulose microfibril angle rather than changes in secondary growth or tissue geometry. Domestication did not significantly modify "large-scale" trait development or growth form plasticity, since both wild and domesticated manioc can develop as shrubs or lianas. However, "finer-scale" developmental traits crucial to mechanical stability and thus ecological success of the plant were significantly modified. This profoundly influenced the likelihood of brittle failure, particularly in long climbing stems, thereby also influencing the survival of the domesticate in natural situations vulnerable to mechanical perturbation. We discuss the different selective pressures that could explain evolutionary modifications of stem biomechanical properties under domestication in manioc.
驯化可以影响植物的许多功能特征，从整体生活史和生长形式到木材密度和细胞壁超微结构。这些变化可以提高驯化植物在农业环境中的适应性，但可能会对其在野外的生存产生负面影响。我们通过比较来自亚马逊河流域两个不同地区的驯化和祖先生长的野生种，研究了驯化对木薯茎部生物力学的影响。我们比较了机械性能、组织结构和木材特性，包括微纤维角，这些特性在两种不同栖息地（森林或稀树草原）生长的野生和驯化植物中都有所体现，而且生长形式（灌木或藤本植物）也有所不同。野生种在开阔的稀树草原中以灌木形式生长，但在过度生长和森林化的栖息地中以藤本形式生长。驯化木薯保留了生长形式的可塑性。然而，驯化植物的茎部表现出脆性破坏。野生植物在灌木和藤本形态之间的机械结构上存在差异，这种差异在驯化植物的灌木和藤本之间有所减弱。与驯化植物的灌木和藤本形态相比，野生植物的茎部通常更硬，在更高的弯曲应力下失效，并且不易发生脆性断裂。野生和驯化植物茎部之间的生物力学差异主要归因于木材密度和纤维素微纤维角的变化，而不是次生生长或组织几何形状的变化。驯化并没有显著改变“大规模”性状发育或生长形式的可塑性，因为野生和驯化的木薯都可以发育成灌木或藤本植物。然而，对机械稳定性至关重要的“更精细”发育特征发生了显著变化，从而显著影响了植物的脆性破坏的可能性，特别是在长的攀爬茎中，从而也影响了驯化植物在易受机械干扰的自然情况下的生存能力。我们讨论了在驯化过程中可能导致木薯茎部生物力学特性进化改变的不同选择压力。
