Effect of plant age on water content in crowns of fall rye and winter wheat cultivars differing in snow mold resistance

Abstract

. 2001. Effect of plant age on water content in crowns of fall rye and winter wheat cultivars differing in snow mold resistance. Can. J. Plant Sci. 81: 541-550. Resistance to snow molds in winter wheat increases with plant age, and older plants express higher levels of resistance than young plants. Experiments were conducted to study the effect of plant age on percent crown water content (%CWC) and dry weights in fall rye and winter wheat cultivars grown under controlled environments and in the field at Lethbridge, AB. Under controlled environments, the oldest (6 wk of pre-hardening growth at 20°C) treatments accumulated the greatest dry weights following exposure of plants to 1 to 6 wk hardening conditions at 2°C, compared with younger (1 to 4 wk pre-hardening growth) treatments. Exposure of plants to hardening temperatures had the greatest effect on %CWC values, which decreased, gradually, from 82-89% (4.95-8.67 g H 2 O g -1 DW) in unhardened treatments to 67-72% (2.05-2.65 g H 2 O g -1 DW) in plants receiving the 6 wk pre-hardening and 6 wk hardening growth. However, the oldest treatments (4 to 6 wk pre-hardening growth) always exhibited the lowest %CWC values among all hardening treatments. The %CWC in the oldest (6 wk) unhardened plants was also lower ( × = 80.8% or 4.24 g H 2 O g -1 DW) than in the youngest (1 wk) unhardened plants ( × = 91.2% or 11.31 g H 2 O g -1 DW ), demonstrating that water loss occurs in older plants in the absence of low hardening temperatures. In a field study at Lethbridge during the autumn, winter, and early spring of 1997-1998 and 1998-1999, different seeding dates were employed to obtain plants differing in age and developmental state. The %CWC in earlyseeded treatments was lower during the autumn, and remained lower in early spring, compared with later seeded cultivars. The %CWC in crowns was negatively associated with the snow mold resistance rating of a fall rye and five winter wheat cultivars under controlled environment conditions, and among a fall rye and 13 winter wheat cultivars in the field; the highest correlation values in the field were observed from mid-November to mid-March during 1997-1998 (r = -0.84), and 1998-1999 (r = -0.76). These results indicate that the type of snow mold resistance that increases with plant age is related to the accumulation of crown dry matter and the ability of wheat and rye plants to lose crown water in response to both extended growth at warm temperatures and hardening at low, above freezing temperatures. 541-550. Chez le blé d'hiver, la résistance à la moisissure des neiges s'accroît avec l'âge, si bien que les plants plus âgés y résistent mieux que les jeunes. Les auteurs ont étudié les effets de l'âge de la plante sur la concentration d'eau dans la couronne (% CEC) et sur le poids sec des cultivars de seigle d'automne et de blé d'hiver cultivés en milieu contrôlé et au champ à Lethbridge (Alberta). En milieu contrôlé, les traitements les plus longs (6 semaines de culture à 20°C) débouchent sur le poids sec le plus élevé après acc...

Changes in plant chemical defenses and nutritional quality as a function of ontogeny in Plantago lanceolata (Plantaginaceae)

“…Similar decreases in nutritional quality have been observed in numerous plant taxa (e.g., Gaudet et al 2001;Bowers and Stamp 1993;Goodger et al 2006;Merilo et al 2009), directly inXuenced by plant age or indirectly mediated through their correlation with other ontogenetic shifts in leaf anatomy and physiology (Apple et al 2002;Ishida et al 2005). In our study, ontogenetic variation in nutritional quality encompassed an average decrease of 10% in percentage water and 30% in nitrogen concentration from 3-to 18-week-old plants (Fig.…”

“…SpeciWcally for this system, similar variation in leaf nitrogen content (»30%) among individuals of P. lanceolata resulted in a signiWcant eVect on oviposition preferences of the specialist Buckeye butterXy (Junonia coenia, Nymphalidae), with females showing preference for high-nitrogen plants (Prudic et al 2005). Thus, the ontogenetic trajectories in nutritional quality showed here may also help to explain temporal variation in species interactions as seen in other systems (e.g., Gaudet et al 2001;Barrett and Agrawal 2004).…”