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Efficient selection for salt tolerance using the choice of physiological traits is of great importance. In the present study, seven ecotypes of Panicum antidotale (four from the Cholistan Desert an...

Ecotypic specialization among populations within plant species can result in adaptational lag when the climate changes directionally. However, disturbances, whether caused by direct effects of human activities or indirect effects such as climate change, may represent zones within which natural selection is relaxed. We compared the genetically based variation in leaf morphology in Dryas octopetala within three natural populations arrayed along a snowbank gradient, to that found in a recently colonized gravel pad less than 100 m away (1600 total leaf lengths measured; 4 sites × 10 transects/site × 4 plants/transect × 10 leaves/plant). Elevated among-clone leaf length variation within the disturbed site supported the idea that disturbances may represent “hotspots” of evolutionarily significant genetic variation. In the Arctic, where colonization of disturbances is primarily by native species, adaptive evolution may be more rapid than previously thought due to relaxation of selection and subsequent m...

To identify ecotypic variation of L. chinensis, the physiological characteristics and environmental factors were measured and assessed for grey-green and yellow-green ecotypes of L. chinensis grown in the salt-alkalized and aeolian sandy soils. Although both ecotypes presented a similar salt-alkaline tolerance under the experimental conditions, they differed in several aspects. The L. chinensis grown in the aeolian sandy soils had higher water potential and chlorophyll content and lower proline content in their leaves than those grown in the salt-alkalized habitat, and the grey-green ecotype of L. chinensis in both types of soils had higher water potential, chlorophyll and proline contents than the yellow-green ecotype. Besides, grey-green ecotypes had higher salt-alkaline tolerance than the yellow-green ecotype. The stepwise regression analysis showed that soil conductance and pH value were the main ecological factors affecting the physiology of L. chinensis. From the natural distribution of the...

Morphological and physiological variation of four geographically separated European populations of Oxyria digyna (L.) Hill (Polygonaceae) ranging from 45 to 78°N latitude were studied in controlled environments. Characters such as the presence of rhizomes, variable stamen number, few inflorescence branches, and low leaf length/width ratio were found to be common to northern populations. Perennating buds were formed under short day (SD) conditions in all populations across the temperature range (9–21°C), while induction of dormancy required the combination of SD and low temperature. Dormancy release of dormant buds required long day (LD) conditions only. The species was found to be a short-long-day plant for flowering control, the SD requirement being quantitative while the subsequent LD requirement is obligatory. Both the SD flowering response and the fecundity of flowering decreased clinally with increasing latitude of population origin, while the critical daylength for secondary floral inductio...

In beech (Fagus crenata Blume) forests on the Pacific Ocean side in Central Japan, snowpack depth is little and xeric conditions may prevail in winter, in contrast to heavy snow in beech forests on the Japan Sea side. The effects of such conditions during winter on the viability of beech seeds were studied at a beech forest on the Pacific Ocean side. Thickness and weight ratio of pericarp of beech seeds were significantly greater in populations on the Pacific Ocean side compared to the Japan Sea side, this apparently being related to snowpack depth in winter. During the initial stage of seed drying, the drying rate of seeds from the Fuji population (the Pacific Ocean side) was less than that from the Sumon population (the Japan Sea side), possibly due to the thicker pericarp. Germination percentage of seeds which dried to a water content as low as 7% d.w. did not decrease for either population, indicating desiccation tolerance of beech seeds. In the beech forest (University Forest at Yamanaka) on the Pacific Ocean side, water content of seeds sown below litter from both populations remained sufficient for viability during winter. Germinating seeds from the populations on the Japan Sea side were more desiccation-sensitive in early spring, compared to those from the Fuji population, partially due possibly to differences in pericarp thickness.

The temperature requirements for growth and the upper survival temperatures (USTs) of the Antarctic-Arctic disjunct green alga Acrosiphonia arcta and of the Arctic/cold-temperature A. sonderi (Acrosiphoniales) from several localities within their distribution areas were determined. Ecotypic variation with regard to growth optima as well as survival temperatures was demonstrated in both species. While cold-temperature strains had relatively high or optimal growth rates at 15°C, polar isolates had very low rates at this temperature and showed growth optima between 0 and 10°C. The UST of the polar isolates of A. arcta is 22°C, i.e. slightly lower than those of the cold-temperate strains at 23–25°C. The cold-temperate isolate of A. sonderi survived 25°C, whereas Arctic strains had USTs of 22–24°C. The data indicate that changes in growth responses to temperature as well as small changes in UST can be achieved in relatively short time periods of exposure to low temperatures (3 million years) as exemplified in ...

Seasonal variation in frost hardiness was evaluated in a number of populations of the indigenous shrub Leptospermum scoparium (manuka). The seed was collected from wild populations at sites ranging from North Auckland to mid Canterbury but germinated and grown outdoors in a common environment in Palmerston North. For comparison, an Australian species, L. rupestre, was included. One-year-old seedlings were exposed to controlled frosts on four occasions throughout a year. Visual damage was measured four weeks after the frosts as the percentage of foliage damage, and frost hardiness was determined as that temperature causing an average of 30% leaf damage. The seasonal minimum frost hardiness in midsummer was similar for each population at about 4°C,whereas the maximum winter hardiness varied from about -5°C in a low altitude (200 m), northern population to -8°C in a high altitude (1000 m), southern population. Leptospermum rupestre had a comparable maximum frost hardiness to the most hardy L. scopar...

Photosynthesis (by 14CO2 uptake) and stomatal conductance of attached ponderosa pine (Pinus ponderosa Laws.) needles were studied in relation to cumulative incident ozone dose in a stand of sapling trees in the San Bernardino National Forest. These trees have been exposed to long-term O3 fumigations throughout their history. A steady-state, ventilated, minicuvette system was used to measure photosynthesis and conductance at light saturation (photon flux density > 1000 μeinsteins m−2s−1), 20°C, and a vapor pressure gradient (needle to air) of 14 mb. Nine trees were stratified into three chronic injury classes (I, slight; II, moderate; III, severe) of three trees each, based on morphological O3 injury symptoms, and the trees were sampled monthly from May to October of 1977. Although these three injury classes grew in a similar environment, they had differential photosynthetic and stomatal responses, suggesting ecotypic variation in O3 sensitivity. The decline in photosynthesis and stomatal function normally...

Accurately identifying the North American cattails (Typha) is important in lake management because Typha is ecologically important and the species differ in ecologically significant ways. Known ecological differences in geographical and ecological range, competitiveness, water-level tolerance, structure and density of shoots, sexual reproduction, and damage by insect parasites are reviewed. Narrow-leaved cattail (T. angustifolia) and hybrid cattail (T. X glauca = T. angustifolia X latifolia) are apparently spreading, often replacing T. latifolia in many disturbed, eutrophic sites in northeastern and north central regions. T. angustifolia and southern cattail (T. domingensis) indicate unstable habitat and nutrient-rich or brackish soil and have more vegetative and flowering shoots per unit area; hybrids suggest habitat disturbance; mixtures of species or seedlings from hybrids may improve success of stands in temporally or spacially variable environments. Ecotypic variation should be considered in...