Cold hardiness and water relations parameters in Rhododendron cv. Catawbiense Boursault subjected to drought episodes

Abstract

We determined whether increase in cold hardiness of Rhododendron cv. Catawbiense Boursault induced by water stress was correlated with changes in tissue water relations. Water content of the growing medium was either maintained near field capacity for the duration of the study or plants were subjected to drought episodes at different times between 15 July and 19 February. Watering during a drought episode was delayed until soil water content decreased below 0.4 m3 m−3 then watering was resumed at a level to maintain soil water content between 0.3 and 0.4 m3 m−3. Cold hardiness was evaluated in the laboratory with freeze tolerance tests on detached leaves. Water relations parameters were determined using pressure‐volume analysis. Exposure to drought episodes increased cold hardiness during the cold acclimation stage in late summer and fall but not during the winter. When water‐stressed plants were re‐watered to field capacity, the previous gain in cold hardiness gradually disappeared. Water relations parameters correlating with seasonal changes of cold hardiness included dry matter content (r =−0.67). apoplastic water content (r =−0.60), and water potential at the turgor loss point (r = 0.40). Changes of cold hardiness in water‐stressed plants in reference to well‐watered plants were correlated with changes of all water relations parameters, except for osmotic potential at full turgor (r = 0.13). It is proposed that water stress reduced the hydration of cell walls, thereby increasing their rigidity. Increased rigidity of cell walls could result in a development of greater negative turgor pressures at subfreezing temperatures and therefore increased resistance to freeze dehydration.

Summer freezing resistance decreased in high-elevation plants exposed to experimental warming in the central Chilean Andes

“…For instance, water-stressed plants accumulate a higher concentration of solutes (i.e. sugars, proteins) in their tissues that depress FP (Chen et al 1977;Goldstein et al 1985;Anisko and Lindstrom 1996). However, we found that FP increased in the leaves of plants growing inside OTCs, suggesting that plants growing under warmer conditions modify the processes of ice formation in their tissues rather than adjust the osmotic potential of their tissues in response to an increase in the soil water deficit.…”

Freezing resistance varies within the growing season and with elevation in high‐Andean species of central Chile

“…Several studies have reported that water‐soluble carbohydrates depress FP, and their accumulation is positively related to drought survival (Streeter et al ., 2001; Merchant et al ., 2006; Monson et al ., 2006). Moreover, other studies reported that the lower FP of water‐stressed plants result from a higher of solute concentration in their tissues (Chen et al ., 1977; Goldstein et al ., 1985; Anisko & Lindstrom, 1996). Hence, decreases in the FP at the end of the growing season are likely to be related to plant responses to drought rather than to ambient temperatures alone.…”

Leaf cold acclimation and freezing injury in C3 and C4 grasses of the Mongolian Plateau

“…Frost injury in freezing-sensitive species is induced mainly through extracellular ice formation, which dehydrates mesophyll tissues by extracting symplastic water, but may directly disrupt the bundle sheath cells of C 4 plants (Ashworth and Pearce, 2002). However, by altering their biochemical composition under chilling temperatures, cold-acclimated plants can accumulate compatible osmolytes in cells, which cause a decline in water potential and increase resistance to dehydration (Goldstein et al , 1985; Aniśko and Lindstrom, 1996), also improving their resistance to freezing (Smallwood and Bowles, 2002). The data reported here are consistent with this mechanism, showing that values of Ψ leaf and Ψ osmotic decreased in plants exposed to the chilling pre-treatment, indicating significant osmoregulation, especially for those in the cold-acclimating group (Fig.…”