Samples of 'red snow' occurring in shaded areas in Mt. Seymour Park, British Columbia, were studied in the field and laboratory. The dominant alga is the volvocalean form Sphaerellopsis rubra nov. sp. The light- and temperature-sensitive organism has been observed in living collections and attempts to culture it have been unsuccessful. The habitat of the new taxon is discussed as well as its relation to the ubiquitous 'red snow alga', Chlamydomonas nivalis.
A study was made of the effect of a single generation of the root-knot nematode Metoidogyne incognita on the growth of potted French bean plants (Pliaseolus vulgaris) inoculated at different stages of plant maturity. In separate experiments, 3-, 11-and 13-day-old plants were inoculated before primary leaf expansion (BPLE), at the appearance of trifoliate leaves (TRIF) and at the flower bud (BDS) stages respectively, with 0, 2000, 4000 or 8000 second-stage juvenile nematodes and maintained in a growth chamber under controlled conditions. The photosynthetic rate of the plants inoculated at the TRIF and BDS stages decreased significantly with increasing inoculum level 7 days after inoculation. Although the respiration rate did not significantly change throughout the experimental period, the ratio of photosynthetic to respiration rate decreased significantly with increasing nematode inoculum level and duration of infection. Chlorophyll content, plant dry weight and the numbers of buds, flowers, pods and seeds were significantly lower in infected plants than in the controls; this effect increased with increasing levels of nematode inoculum for all three plant stages. The leaf area was significantly smaller only when nematode infection occurred at the BPLE stage. The plants which were youngest at the time of nematode infection produced the lowest yield; this appeared to result from the effect of nematodes on photosynthesis and related physiological processes.
Photosynthetic activity of intact nursery-grown white spruce (Piceaglauca (Moench) Voss) seedlings was assessed by measuring CO2 exchange (apparent photosynthesis) and normalized, integrated variable chlorophyll fluorescence emission. Agreement between fluorescence and apparent photosynthesis indicated that photosynthetic inactivation of seedlings from selected seedlots began in mid-August and approached completion in late October. Inactivation occurred somewhat earlier in northern seedlot seedlings than in those from a more southerly provenance. Seedlings tested in late October showed significant photosynthetic inactivation, as indicated by both fluorescence and apparent photosynthesis. These seedlings also had passed the −18 °C frost hardiness test currently used in British Columbia as an indicator for safe lifting. On removal from −2 °C storage, seedlings lifted and stored according to nursery practises showed fluorescence emission indicative of photosynthetic reactivation and also had high root growth capacity scores. Low root growth capacity scores were associated with delayed or incomplete photosynthetic reactivation. These results show that fluorescence assessment provides information about the physiological status of white spruce seedlings. Variable fluorescence assays are nondestructive and can be made and interpreted within minutes. As an indicator of shoot metabolic activity, fluorescence assessment provides information useful in selecting lifting dates and in evaluating the effects of dark cold storage on white spruce seedlings.
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