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  • Author or Editor: Carol A. Hartley x
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Twenty-five female clones of Fragaria chiloensis (L.) Duchesene collected from the California and Oregon coasts were surveyed for gas exchange rates under field conditions. Carbon assimilation (A) rates of native clones were 25% to 69% higher than for `Totem' (Fragaria × ananassa Duchesne) on a leaf-area basis (μmol of CO2 per sec/m2) and 7% to 77% higher when expressed on a leaf dry-weight basis (μmol of CO2 per kg dry wt/sec). Higher rates of stomatal conductance (gs) were observed in 16 of 25 F. chiloensis clones than in `Totem', with nine of 25 clones also having higher rates of transpiration (E). All clones had higher rates of residual conductance (gr) and greater water use efficiency (WUE) than the cultivated standard. The gas exchange characteristics of four strawberry cultivars (F. × ananassa) and four F. chiloensis genotypes were compared under standard greenhouse conditions. F. chiloensis genotypes had higher rates of A than cultivars when expressed on per leaf-area and dry-weight bases. Native clones also had higher rates of gs, gr, E, and WUE and greater quantum yield. Differences in chlorophyll content were observed among genotypes, but not between species.

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In the early spring, 300 canes of `Meeker' red raspberry were tagged and 150 were deflowered at anthesis. During a 12-week period beginning at anthesis, leaves were sampled for anatomical sectioning and determination of chlorophyll content and dry weight per leaf unit area,

Comparisons of leaf cross-sections from fruiting (F) and deflowered (DF) canes demonstrated high levels of starch accumulation in the latter. This accumulation of starch was layered throughout the cross section, and size of starch crystals varied by location. Dry weight per leaf unit area increased in all leaves during the season, but was consistently greater in leaves of DF canes throughout the season.

Total leaf chlorophyll and chlorophyll a content increased until reaching a maximum three weeks after anthesis, Both decreased slightly until nine weeks after anthesis and sharply thereafter as leaves began to senesce. Chlorophyll b content remained nearly constant until eight weeks after anthesis at which time levels declined during the onset of senescence.

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At two-week intervals from 17 June to 15 July, three groups of `Meeker' red raspberry plants were infested with two-spotted spider mites (Tetranychus urticae) in a greenhouse. While populations on individual plants were allowed to develop freely, control plants were kept free of mites with a chemical miticide. Gas exchange measurements were made on 27 July prior to visible mite damage, and on 7 October after injury was apparent. The relationships between mite populations and leaf gas exchange and chlorophyll characteristics were described using a logarithmic function.

Physiological responses to mite feeding were observed prior to visible leaf injury. On both dates, CO2 assimilation rates decreased (p ≤ 0.001) with increasing mite numbers per leaflet. On 27 June, a significant relationship (R2 = 0.61***) was found between mite number and mesophyll conductance (gm). On 7 October, significant relationships (p ≤ 0.001) were also observed with gm, stomatal conductance (gs), and transpiration (E). Total chlorophyll content of leaves decreased with increasing mite populations, but chlorophyll a/b ratio and dry weight per leaf unit area were unchanged.

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In the early spring, 300 canes of `Meeker' red raspberry were tagged and 150 were deflowered at anthesis. During a 12-week period beginning at anthesis, leaves were sampled for anatomical sectioning and determination of chlorophyll content and dry weight per leaf unit area,

Comparisons of leaf cross-sections from fruiting (F) and deflowered (DF) canes demonstrated high levels of starch accumulation in the latter. This accumulation of starch was layered throughout the cross section, and size of starch crystals varied by location. Dry weight per leaf unit area increased in all leaves during the season, but was consistently greater in leaves of DF canes throughout the season.

Total leaf chlorophyll and chlorophyll a content increased until reaching a maximum three weeks after anthesis, Both decreased slightly until nine weeks after anthesis and sharply thereafter as leaves began to senesce. Chlorophyll b content remained nearly constant until eight weeks after anthesis at which time levels declined during the onset of senescence.

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