120 COLLOQUIUM 3 (Abstr. 1000-1005) Seedling Morphological and Physiological Adaptation to Abiotic Stress
survival rate associated with AP. To date, little information is available on the temporal changes in root morphology, physiology, and anatomy of seedlings in response to AP. Platycladus orientalis (L.). Franco, a native Chinese Cupressaceae plant, is among
crop production and corresponding economic benefits to growers. Thus, the effective production of high-quality seedlings is of great significance for researchers and farmers. Morphological and physiological characteristics of vegetable seedlings are
Studies based on X-ray photographs were conducted to predict the morphology of tomato (Lycopersicon esculentum Mill.) seedlings at transplanting stage. Currently, seed-lot quality of tomato seeds for growing commercial transplants is determined with grow-out tests in the greenhouse because the standard germination test fails to predict the percentage of normal or usable transplants (UTs). These grow-out tests, however, are difficult to standardize. An X-ray evaluation procedure is presented as an alternative. X-ray images nondestructively provide information on embryo size and morphology and the amount of endosperm and the area of free space. These parameters correlate well with the morphology of 14-day old seedlings. Cotyledon morphology has the highest correlation with the percentage of UTs. A test based on the evaluation of X-ray images, classifying the cotyledon morphology and seed free space, predicts the percentage of UTs more accurately than the currently used germination test. A second method based on an equation that uses the probabilities of all X-ray categories proportionally predicts the percentage of UTs of primed seeds more accurately than the first method. Selecting individual seeds based on X-ray images has the potential to raise the percentage of UTs of seed lots. On the average, the percentage of UTs of control seeds was 22% higher after hand selection based on X-ray evaluation. Primed seeds gave 12% higher results. Hence, X-ray analysis can predict seedling performance and enable the selection of high-quality seeds.
Buffalograss [Buchloë dactyloides (Nutt.) Engelm.] is a warm-season perennial grass native to the North American Great Plains region and has been used as a low-maintenance turfgrass. Turf-type buffalograsses are available and are commonly used on nonirrigated land. Our objectives were to determine the deepest planting depth of burrs that would allow acceptable emergence, and to evaluate planting depth effects on buffalograss seedling morphology. Two greenhouse experiments were conducted in Fall 2000. Experimental design was a randomized complete block with 4 replications and a 3 (cultivar) × 6 (planting depth) factorial treatment arrangement. Results showed that buffalograss emergence decreased as planting depth increased. All cultivars had <10% total emergence at planting depths >50 mm. Emergence rate indices were greatest when planting depth was 13 mm and were significantly lower at planting depths of 51 and 76 mm. Average coleoptile length was 11 mm. Coleoptile length was similar between all planting depths except for the 13 mm depth which resulted in 9-mm-long coleoptile. Subcoleoptile internode length increased with planting depth up to 38 mm. Planting depths deeper than 38 mm did not significantly increase subcoleoptile internode length.
Weight and morphological characteristics of red raspberry (Rubus idaeus L.) fruit, including drupelets (height, diameter, number), receptacle cavities (depth, diameter), and pits (individual weight), were measured on 78 seedlings from the cross `Chief' × `Chilliwack'. Fruit strength, as measured by compression, correlated with fruit weight, drupelet number, receptacle cavity depth, and individual pit weight. Fruit weight was positively correlated with all morphological characteristics. Individual pit weight, drupelet height, and drupelet number provided the largest component contributions to fruit strength as measured by path analysis.
For accelerating the filling in of bare areas in native lowbush blueberry fields or converting new areas to production, micropropagated plantlets rooted after three subcultures outperformed seedlings and rooted softwood cuttings. After 2 years of field growth, they averaged 20.3 rhizomes each of average dry weight 3.5 g, as compared with 5.7 rhizomes of average dry weight 1.1 g for rooted softwood cuttings. After 1 year of field growth, seedlings produced on average 3.3 vs. 0.4 rhizomes from micropropagated plants that had not been subcultured and 0.3 rhizomes from stem cuttings. Apparently, subculturing on cytokinin-rich media induces the juvenile branching characteristic that provides micropropagated plants with the desirable morphologies and growth habits of seedlings. These characteristics favor rhizome production while the benefits of asexual reproduction are retained. The advantage in rhizome production of micropropagation over stem cuttings varied among clones.
104 POSTER SESSION (Abstr. 389–396) Seedling Establishment
The effects of different dormancy-induction regimes on first-year containerized coastal Douglas fir [Pseudotsuga menziesii (Mirb.) Franco var. menziesii] seedling morphology and physiology in the nursery, as well as seedling survival and performance after one growing season in a common garden, were investigated. In early July, three dormancy-induction regimes were applied: moderate moisture stress (MS), short day (SD), and short day with moderate moisture stress (SD+MS). In early October, seedling height, root collar diameter, and shoot dry weight were unaffected by regime, but root dry weight was reduced in seedlings from the MS and SD+MS regimes compared with the SD regime. At this time, morphogenesis was completed in all terminal buds of seedlings from both SD regimes, whereas it continued in all terminal buds of seedlings from the MS regime. Furthermore, 25% to 88% of terminal buds from the SD regimes were endodormant, but none from the MS regime were endodormant. In March, budbreak occurred at the same time in seedlings from the two SD regimes and was earlier than in seedlings from the MS regime; root growth capacity was unaffected by regime. After one growing season, there were no regime differences in seedling survival, root collar diameter, shoot dry weight, root dry weight, length of the current-year leader, or number of needles on the leader.
held at the 91st ASHS Annual Meeting Corvallis, Ore. 9 Aug. 1994 sponsored by the Seedling Establishment Working Group Environmental Stress Physiology Working Group Root Growth and Rhizophere Dynamics Working Group Seed Research Working Group