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Vigour was measured using computer-aided analysis of digital images in six seed lots of Impatiens that differed in vigour but retained greater than 86% standard germination. Seed lots that differed in initial seed vigour were selected based on the commercially used Ball Vigour Index and vigour independently assessed using saturated salts accelerated aging tests. Digital images were captured from seeds germinated in Petri dishes placed on a flat-bed scanner. Seedling growth was measured daily for four days following initial radicle protrusion using commercially available root length calculating software. Seedling size and growth rate generally ranked seed lots from high to low vigour in a similar way compared to the Ball Vigour Index and saturated salts accelerated aging tests. The exception was that seed lot #2 was identified as the highest vigour seed lot using seedling growth parameters rather than seed lot #1. However, high and low vigour seed lots were identified as well with seedling growth measurements compared to the other two vigour tests used to evaluate Impatiens seed lots. Additionally, two vigour indices were calculated for seedling length using standard deviation as a measure of population uniformity. Both indices showed less ability to statistically separate seed lots compared to growth measurements alone. The current study showed that computer-aided analysis of digital images could be used successfully to rank seed lot vigour in Impatiens based on seedling length.

Chia (Salvia hispanica L.) is an oil seed crop, with a high ω‐3 fatty acid and fiber content, used for food and medicine. Upon imbibition, seeds (nutlets) exude a pectinaceous mucilage. The impact of mucilage on seed germination under different environments is unknown. The objectives of this study were to investigate the potential impact of mucilage on chia seeds germinated under conditions of biotic and abiotic stress. Chia seeds were germinated with or without mucilage under various stress conditions in lab and greenhouse studies. Germination conditions included exposure to water, cold, heat, salt stress, and fungal infection. The mucilage was removed following hydration with an acid wash without impacting germination. There was no difference in final germination percentage of seeds with or without mucilage under optimal lab conditions. However, seeds with mucilage removed germinated more slowly, with 63% germination after 26 h compared with 97% in seeds producing mucilage. Seed germination on polyethylene glycol solutions with increasingly negative water potentials was reduced in seeds without mucilage. Seeds with mucilage production that were exposed to cycles of wetting and drying germinated better and faster than non‐mucilage‐containing seeds. Greenhouse emergence showed a similar trend, with mucilage‐producing seeds having greater emergence at lower substrate moisture levels. Under saline conditions, mucilage‐producing seeds germinated 48% higher than non‐mucilage‐producing seeds at 200 mM NaCl. The data suggest that seed mucilage production may impart an ecological advantage in arid or semiarid habitats with irregular soil moisture or soils with high salt levels.

Rooting stage, transpiration capacity, and relative water content were measured in cuttings every 5 days for 25 days. Cell divisions in phloem parenchyma were evident between 5 and 10 days after sticking, organized subcuticular root primordia were present between 10 and 12 days, and roots emerged between 12 and 15 days. Transpiration was measured in poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch `Freedom Dark Red') cuttings under light or dark conditions at increasing vapor pressure deficit (VPDair) levels during different stages of rooting. Transpiration capacity did not increase until roots emerged on the cuttings. Light had a significant impact on transpiration rates only after roots emerged. Light was more significant than VPDair for determining actual transpiration. Between visible rooting (15 days) and 25 days, increase in total root length was linear (r2 = 0.92) and significantly correlated with transpiration (r2 = 0.98). Transpiration capacity increased after visible rooting, but did not significantly increase under non-misted conditions until cuttings were well-rooted and had a total root length >50 cm (18 days after sticking). Relative water content measured before and after entering the transpiration chamber confirmed that cuttings were only able to take enough water from the medium to continue sustained transpiration after 18 days. A cutting coefficient was developed from transpiration data to modify the misting interval for dynamic controlled misting. Greenhouse studies showed a 55% or greater reduction in water use with dynamic control compared to constant static or stepped down static control. Rooting performance was unaffected by misting interval. Foliar nutrition was significantly reduced in all cuttings after 7 days in the mist bench, but changes in foliar elemental content were not correlated with misting interval.

Early seedling growth rate can be used to estimate seed vigor for small-seeded vegetable and flower seeds. However, hand measurement of small seedlings is tedious and difficult to reproduce among analysts. Computer-aided analysis digital images of seedlings should improve accuracy and reproducibility. A flat-bed scanner fitted with base and top lighting provided high resolution images of even small-seeded species like petunia [Petunia ×hybrida `Blue Picotee' (Hort) Vilm.] and lisianthus [Eustoma grandiflorum `Mariachi Pure White' (Raf.) Shinn]. Uniform lighting was provided and images were captured and analyzed in less than 2 minutes. A clear, cellulose film was used as the germination substrate in petri dish germination assays to facilitate capturing images with a flat-bed scanner. The transparent medium permitted seedlings to be imaged without removal from the petri dish and also allowed for repeated measures of the same seedlings in order to calculate growth rate. Six species evaluated in this study included cauliflower (Brassica oleracea L., var. Botrytis), tomato (Lycopersicon esculentum Mill. `New Yorker'), pepper (Capsicum annuum L. `North Star'), impatiens [Impatiens walleriana Hook. f. `Impact Lavender'], vinca [Catharanthus roseus (L.) G. Don. `Little Bright Eye'], and marigold (Tagetes patula L. `Little Devil Flame'). For germination and early seedling growth, the cellulose film compared favorably with other standard germination media (blue blotter and germination paper) for five of the six species tested. Computer analysis of seedling length was possible for all six species and was statistically similar to hand measurements averaged for three analysts.

Damage and degradation of cellular proteins is observed during seed deterioration due to aging. L-isoaspartyl methyltransferase (EC 2.1.1.77) is an enzyme hypothesized to play a role in limiting and repairing aging-induced damage of proteins. Tomato seeds (Lycopersicon esculentum `New Yorker') were assayed for changes in L-isoaspartyl methyltransferase activity during accelerated aging and after osmotic priming. Accelerated aging of seeds for 1 to 4 days at 45°C and 100% humidity reduced germination from 94% to 71%, the mean time of germination (MTG) increased from 2.4 to 5.8 days and was accompanied by a correlative decrease in L-isoaspartyl methyltransferase activity R2 = 0.90. Aged and untreated seeds were primed for 7 days at 20°C in darkness using aerated solutions of 3% KNO3 or polyethylene glycol 8000 (PEG) with equivalent osmotic potential (–1.25 MPa). Priming with KNO3 decreased the MTG but not germination percentage for untreated seeds. Priming did not affect L-isoaspartyl methyltransferase activity in untreated seeds but restored activity in aged seeds primed in KNO3 to levels near that of untreated seeds. Priming with PEG did not effectively improve the MTG or increase L-isoaspartyl methyltransferase activity. During germination, enzyme activity remained constant for 48 hours post-imbibition and then declined suggesting the enzyme was developmentally regulated and inactivated or degraded as radicle emergence occurred.

High germination seed lots of purple coneflower [Echinacea purpurea (L.) Moench] were evaluated for laboratory germination following osmotic priming or chilling stratification. Compared to nontreated seeds, osmotic priming at 25C in salts (KNO3 + K3PO4; 1:1, w/w) or polyethylene glycol 4000 (PEG) increased early (3-day) germination percentage at 27C of all seed lots, and improved total (10-day) germination percentage of low-germination seed lots. Total germination percentage was unaffected or increased by priming for 4 days compared to 8 days, and by priming at –1.0 MPa compared to –0.5 MPa (except for one low-germination seed lot). Chilling stratification in water at 5 or 10C increased early and total germination of all seed lots, except for that same lot, compared to nontreated seeds. Total germination percentage was unaffected or increased by stratification at 10C rather than at 5C. Neither extending stratification ≥20 days nor lowering osmotic potential with PEG during stratification improved total germination percentage.