Kelly David
Botany and Zoology Dept, Massey University, Palmerston North, New Zealand.
Oecologia. 1985 Sep;67(2):292-294. doi: 10.1007/BF00384302.
Most so-called biennial plants may flower in their second growing season, but usually take longer in the field. Work reported here and in four recent papers on six different species has identified natural populations of strictly biennial plants, which flower only in their second year. The strict biennials and facultative biennials seem to form two distinct groups. All six strict biennial species were growing in infertile sites, and at least four of the six have annual variants at other sites, so they may be regarded as 'extended annuals' growing in sites too infertile for the life cycle to be completed in one year. In contrast most facultative biennials are pauciennials (short-lived monocarpic perennials) of more fertile, disturbed habitats. Moreover, the rigid two-year life cycle of the strict biennials creates at each site two temporally separated sub-populations, which flower in odd and even years.
大多数所谓的二年生植物可能在第二个生长季节开花，但在田间通常需要更长时间。本文以及最近四篇关于六个不同物种的论文所报道的研究，已经确定了严格二年生植物的自然种群，这些植物只在第二年开花。严格二年生植物和兼性二年生植物似乎形成了两个不同的类别。所有六个严格二年生植物物种都生长在贫瘠的地点，并且六个物种中至少有四个在其他地点有一年生变种，所以它们可能被视为在过于贫瘠以至于生命周期无法在一年内完成的地点生长的“延长一年生植物”。相比之下，大多数兼性二年生植物是生长在更肥沃、受干扰生境中的短寿单次结果多年生植物（少果多年生植物）。此外，严格二年生植物严格的两年生命周期在每个地点产生了两个在时间上分离的亚种群，它们在奇数年和偶数年开花。
