© 2005 Heron Publishing—Victoria, Canada
Root temperature drives winter acclimation of shoot water relations in Cryptomeria japonica seedlings
Mariko Norisada (1, 2), Masashi Hara (3), Hisayoshi Yagi (4) and Takeshi Tange (5)
1. Asian Natural Environmental Science Center, The University of Tokyo, Tokyo 113-8657, Japan / 2. Corresponding author (norisada@fr.a.u-tokyo.ac.jp) / 3. Daio Paper Corporation, Ehime 799-0492, Japan / 4. Graduate School of Bioresources, Mie University, Mie 514-8507, Japan / 5. The Tokyo University Forests, The University of Tokyo, Tokyo 113-8657, Japan / Received February 2, 2005; accepted March 27, 2005; published online August 16, 2005
Summary
In many temperate evergreen plant species, reductions in turgor loss point of leaves (Ψtlp) and leaf osmotic potential at full turgor (πsat) occur from late summer to winter. To test the hypothesis that this seasonal change in leaf water relations is driven by
root temperature, we manipulated the temperature of the roots and shoots of Cryptomeria japonica D. Don seedlings separately. Whole-plant warming diminished the seasonal changes in shoot water relations observed in the
control plants, whereas shoot warming did not. Compared with the controls, root warming diminished the change in Ψtlp but not in πsat, whereas cooling accelerated the seasonal changes in shoot water relations. These results indicate that: (1) temperature
responses of roots are involved in the seasonal changes in Ψtlp from late summer to winter; and (2) root temperature is partly responsible for the simultaneous changes in πsat. Whole-plant cooling caused increased root hydraulic resistance, suggesting that seasonal changes in shoot water relations
represent adaptive responses to increased root hydraulic resistance at low root temperatures.
Keywords:
osmotic potential at full turgor, soil cooling, soil warming, turgor loss point.
