PHOTOSYNTHETIC SENSITIVITY TO TEMPERATURE IN POPULATIONS OF TWO C₄BOUTELOUA (POACEAE) SPECIES NATIVE TO DIFFERENT ALTITUDES

Abstract

The relationships between photosynthesis, flowering, and growth temperatures were examined experimentally in four populations of the C4 grass genus Bouteloua. Field‐collected plants were grown under two temperature regimes, cool (20 C day/6 C night) and warm (30/16), representative of the extreme populations. Populations collected from the warm climates had significantly lower photosynthetic capacity when grown in the cool chamber relative to the warm chamber, while photosynthetic capacity in the cool climate populations did not differ between the growth conditions. Additionally, exposure to a 2‐day cold temperature treatment (10/‐2), representative of late‐season frosts in high altitude sites, resulted in further reductions in photosynthesis in the warm climate plants, but not in the cool climate plants. This effect was greater for plants grown in the cool growth chamber. Flowering was reduced by 70% in the warm climate plants grown in the cool chamber, and was correlated with photosynthetic inhibition following the short‐term cold temperature treatment. These results indicate that genetic differentiation for photosynthetic temperature sensitivity has occurred in the cool climate populations, and that long‐term exposure to cool temperatures coupled with short‐term relatively extreme low temperatures results in greater photosynthetic inhibition in nontolerant populations.

Photosynthetic performance at low temperature ofBouteloua gracilisLag., a high‐altitude C4grass from the Rocky Mountains, USA

“…The primary differences between the ecotypes were (1) the low‐elevation plants exhibited higher rates of A across a range of temperature than high‐elevation plants when grown at 26/16 °C; (2) growth at 14/7 °C slightly enhanced A below 18 °C in the high‐elevation ecotype, and slightly depressed it in the low‐elevation ecotype; and (3) the Arrhenius plot for Rubisco activity showed a marked break at 17 °C in the high‐elevation plants, but not the low‐elevation species, indicating there may be changes in Rubisco properties during ecotypic adaptation. These results are consistent with Bowman & Turner’s (1993) observation that a Bouteloua gracilis population from 1400 m in Colorado had higher A than two Rocky Mountain ecotypes from 2600 and 3050 m when all were grown in a common environment. Also, reducing daytime growth temperature from 30 to 20 °C depressed A approximately 20% in the low‐elevation ecotype, but not the high‐elevation ecotypes ( Bowman & Turner 1993).…”

“…These results are consistent with Bowman & Turner’s (1993) observation that a Bouteloua gracilis population from 1400 m in Colorado had higher A than two Rocky Mountain ecotypes from 2600 and 3050 m when all were grown in a common environment. Also, reducing daytime growth temperature from 30 to 20 °C depressed A approximately 20% in the low‐elevation ecotype, but not the high‐elevation ecotypes ( Bowman & Turner 1993). Matsuba et al (1997) observed that Spartina anglica from cool temperate salt marshes had higher A across a range of temperatures following 1–4 weeks at lower growth temperature, while Zoysia japonica , a chilling‐sensitive species from warm climates, had reduced A following the same treatment.…”

“…were collected in August 1996 near Grant, Colorado, USA (39°5′N, 105°30′W; 3000 m) and Dawson Butte, Colorado (39°10′N, 104°30′W; 1500 m), respectively. Mean minimum temperatures during the growing season are 0 °C (June) to 4 °C (July) at the 3000 m location, and 10° to 14 °C near Dawson Butte ( Bowman & Turner 1993; National Weather Service, 1999). Average maximum temperatures for July are 20–23 °C at 3000 m in the central Rockies, and 29–31 °C on the Prairie near Dawson Butte.…”

Effects of Snowmelt Timing and Neighbor Density on the Altitudinal Distribution of Potentilla diversifolia in Western Colorado, U.S.A

“…Above-ground cover is notably lower in P. diversifolia's alpine habitat than in the subalpine zone but it is possible that below-ground competition is important for both alpine and subalpine flora (Griggs, 1956;Theodose and Bowman, 1997). In addition, shading and/or sheltering effects of vegetation, and differences in community and soil albedo may have affected temperature as well as other, less obvious microclimatic variables not measured here (Bowman and Turner, 1993;Gottfried et al, 1998;Arft et al, 1999;Callaway et al, 2002).…”

Controle do desenvolvimento das hastes no capim Tanzânia: um desafio.

“…Além disso, parece haver uma interação entre características genéticas ou evolutivas e temperatura. Em um trabalho com gramíneas C 4 do gênero Bouteloua foi observado que o florescimento era reduzido em 70% quando espécies adaptadas a climas quentes eram submetidas à temperaturas baixas, o que foi atribuído à redução da atividade fotossintética (Bowman & Turner, 1993).…”