© 1997 Heron Publishing—Victoria, Canada
Effects of dessication on post-planting stress in bare-root Corsican pine seedlings
Sabine Girard (1, 2, 3), Andre Clement (2), Herve Cochard (1), Bruno Boulet-Gercourt (3) and Jean-Marc Guehl (1)
1. Equipe Bioclimatologie et Ecophysiologie Forestières, INRA Centre de Nancy, F-54280 Champenoux, France / 2. Equipe Sol et Nutrition, INRA Centre de Nancy, F-54280 Champenoux, France / 3. Institut pour le Développement Forestier, 23 avenue Bosquet, F-75007 Paris, France / Received March 6, 1996
Summary
We examined the post-planting consequences of pre-planting exposure stress on two-year-old, bare-root Corsican pine (Pinus nigra Arnold. ssp. laricio var. Corsicana) seedlings. Seedlings were lifted from a nursery and exposed to ambient conditions for periods of up to 192 h before being
planted in minirhizotrons. Exposure decreased seedling water potential, CO2 assimilation rate, leaf conductance and new root elongation, and increased mortality after planting. During exposure, needle
total nonstructural carbohydrates (TNC) concentration (expressed on a dry mass basis) decreased by 0.31 mg gdm–1 h–1; however, needle and root TNC concentrations remained high (> 100 mg gdm–1) at planting, even in those treatments leading to severe seedling mortality. More than 90% of the seedlings with predawn
water potentials lower than –1.3 MPa at planting did not elongate new roots and did not survive, whereas a similar percentage
of seedlings with a predawn water potential above this value at planting elongated new roots and survived, suggesting that
this value corresponds to a turgor threshold below which new root formation is inhibited. At planting, embolization of xylem
conduits in roots and shoots was low for seedlings in all of the exposure treatments.
Keywords:
CO2 assimilation, embolism, leaf conductance, new root elongation, plant carbohydrate status, plant water status, xylem.
