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Boris Andrés Bran Barrientos and Jong-Yi Fang

Spathoglottis plicata is an attractive, easy-to-grow, and floriferous terrestrial orchid that has become the most important horticulturally cultivated Spathoglottis species in Southeast Asia. The present research was conducted to study the asymbiotic seed germination and seedling development of this orchid under the influence of various photoperiod and medium treatments. Seeds from 28-day-old capsule were sown on five culture media, including half-strength Murashige and Skoog medium (1/2 MS), Orchid Seed Sowing Medium (OSSM), BM-1 Terrestrial Orchid Medium (BM-1), Vacin and Went Modified Orchid Medium (VW), and Knudson C Orchid Medium (KC), and incubated under 0/24-hour or 16/8-hour light/dark photoperiod. Seed germination occurred in all photoperiods and media tested but at different paces. Seeds subjected to total darkness germinated more rapidly in the first 3 weeks than those subjected to light. However, seed germination under light overtook or even exceeded seed germination under dark starting on the fourth week of culture. Seedlings grown on the OSSM and VW media showed the fastest development as they reached the advanced stage (Stage 6) within 11 weeks of culture. Seedlings on the BM-1 medium were the slowest to evolve, as they required more than 16 weeks’ time to complete all the developmental stages. Light-incubated advanced stage seedlings were subcultured on the same medium until leaves and roots were well developed and acclimatized in the greenhouse with 100% survival.

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Brent K. Harbaugh

Rosetting response was determined for four lisianthus [Eustoma grandiflorum (Raf.) Shinn.] cultivars exposed to photoperiod and temperature treatments during stage 1(14 to 43 days after sowing) and stage 2 (43 to 79 days after sowing) seedling development. Stage 1 seedlings were exposed to short days (12 h photoperiod) or long days (18 h photoperiod) in combination with high (26C) or low temperatures (12C). After stage 1 treatments, stage 2 seedlings were divided and exposed to the same treatment combinations resulting in 16 treatments. Seedlings were then grown at 22C for 120 days to determine rosetting response. Cultivars responded differently to temperature and photoperiod. Short day-high temperature exposure during either stage 1 or stage 2 resulted in the greatest number of rosetted plants (50 to 100%) for `Yodel White', `HeidiPink', and `BlueLisa'. `GCREC-Blue' did not rosette with short day-high temperature. Low temperature during stage 1 did not prevent rosetting when stage 2 seedlings were subsequently exposed to high temperature, but low temperature during stage 2 decreased rosetting of seedlings exposed to high temperature in stage 1. Less rosetting occurred with long day-high temperature than with short day-low temperature, especially for `Blue Lisa'.

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Rui Zhang, Fang-Ren Peng, Pan Yan, Fan Cao, Zhuang-Zhuang Liu, Dong-Liang Le, and Peng-Peng Tan

Root systems of pecan trees are usually dominated by a single taproot with few lateral roots, which are commonly thought to inhibit successful transplanting. This study aimed to evaluate early growth and root/shoot development of pecan seedlings in response to taproot pruning. Taproots of ‘Shaoxing’ seedling pecan trees were mildly (1/3 of the total length of the radicle removed) and severely (2/3 of the total length of the radicle removed) pruned at different seedling development stages shortly after germination. At the end of the first growing season, top growth was measured and then trees were uprooted so that root system regrowth could be evaluated. The results showed that root pruning had no impact on increases in stem height or stem diameter. However, pruning the taproot could stimulate primary growth in taproot branches. Root weight and the number of taproot branches per tree increased with decreasing taproot length. This study indicated that severe root pruning when three to five leaves had emerged resulted in root systems with more taproot branches and the greatest root dry weight after one growth season, which may increase survival and reduce transplanting shock.