Hidden from the harsh: Belowground preformation prior to winter determines life history strategy of a temperate perennial herb

Abstract

In temperate mountains, the belowground organ preformation prior to winter is a well-known adaptation strategy in perennial plants, however its detailed phenology is still poorly understood, particularly with reference to belowground floral morphogenesis. Here we investigate, in detail, the developmental stages occuring belowground and its relation with annual aboveground phenology in a temperate Himalayan herb Trillium govanianum. We studied the species at three selected sites along an altitudinal gradient in Kashmir Himalaya. At each site, we recorded the aboveground phenological stages and also studied periodically the overwintering belowground buds to characterize the various developmental stages. We measured the size of leaf and floral organs in the belowground preformed bud and also at anthesis aboveground to investigate the differences at these two stages. The results reveal that the leaves and flower in T. govanianum are preformed belowground one season prior to aboveground development. The species shows an advanced stage of floral morphogenesis and development during the belowground preformation, including completion of male meiosis and formation of functional ovules. We found no significant difference in the floral organs like anther and ovary length in the belowground bud and aboveground anthesis stages, thereby clearly indicating that these essential floral organs are fully developed in the preformed bud much before the species enters into winter dormancy. Our study suggests that the highly developed floral preformation hidden from the harsh winter conditions plays a pivotal role in the life history strategy of this temperate herb. Overall, our findings advance the current understanding of the belowground phenology, particularly the process of preformation in temperate herbaceous plants.