Warming impacts potential germination of non-native plants on the Antarctic Peninsula

The Antarctic Peninsula is under pressure from non-native plants and this risk is expected to increase under climate warming. Establishment and subsequent range expansion of non-native plants depend in part on germination ability under Antarctic conditions, but quantifying these processes has yet to receive detailed study. Viability testing and plant growth responses under simulated Antarctic soil surface conditions over an annual cycle show that 16 non-native species, including grasses, herbs, rushes and a succulent, germinated and continued development under a warming scenario. Thermal germination requirement (degree day sum) was calculated for each species and field soil-temperature recordings indicate that this is satisfied as far south as 72° S. Here, we show that the establishment potential of non-native species, in number and geographical range, is considerably greater than currently suggested by species distribution modelling approaches, with important implications for risk assessments of non-native species along the Antarctic Peninsula.

First report on the germination requirement of Pterygopleurum neurophyllum seeds

Pterygopleurum neurophyllum is a class II endangered species and Red list class CR species in Korea. In this study, we considered the effects of cold stratification on embryo development in P. neurophyllum seeds, and analysed the effect of temperature and light conditions, immersion time in 50% H2SO4 and GA3 concentration on subsequent germination. The embryo of P. neurophyllum seeds showed elongation after four weeks of cold stratification (4°C) and embryo length was significantly increased after eight weeks. Germinated seeds were observed after 12 weeks of cold stratification. The cold-stratified (12 weeks) seeds showed the highest germination (23.1%) at 20°C. After 30 minutes H2SO4 immersion, germination of cold-stratified seeds was 29.4%. The GA3 concentration study showed the highest germination for seeds treated with 0.5 g L-1 GA3 (37.2%). The maximum germination across all treatment combinations was 79.8% for seeds given 30 minutes of 50% H2SO4 treatment and 12 weeks of cold stratification and then treated for 24 hours in 0.5 g L-1 GA3.

Hidden viability risks in the use of farm-saved small-grain seed

SUMMARYAgriculture must provide sustainable food security and economic development to meet future challenges; new cultivars and the use of quality seed will be key components of this. The use of farm-saved seed may increase due to imbalances between income and expenditure associated with farming. The present study characterized the quality of commonly used, and thereby easily available, farm-saved seed in Finland. Farmers provided 657 seed lot samples of spring barley (Hordeum vulgare L.) and spring wheat (Triticum aestivum L.) that they intended to use for sowing. Germination, seed weight, seedling elongation and within-seed-lot variability were analysed. Information was available on region, number of seed generations and cultivar. The specific aims were to identify how many generations of farm-saved seed are generally used by farmers, whether there is any safe generation threshold and the variability of quality of the seed lots. It was found that 0·80–0·84 of barley seed lots exceeded the 0·85 minimum germination requirement for certified seed, but only 0·60 of wheat. The risk of poor establishment was higher in wheat if the seed was not tested: 0·13 of wheat seed lots had germination of ⩽0·65 and 0·06 of ⩽0·50, while for barley the proportions with inadequate germination were 0·03–0·05. At most, >0·30 abnormal seedlings were recorded for barley and >0·50 for wheat. Variation in seed size and seedling length within seed lots was important, and increase in the latter was associated with reduced germination. In combination with up to 0·14 lethal fungus-infected seed, this emphasizes the need for seed upgrading measures. No safe threshold for farm-saved seed generations was determined.

Propagation by Stem Cuttings and Response of Seeds to Light and Temperature of Fever Tea (Lippiajavanica)

Fever tea (Lippiajavanica) is one of the important medicinal plants belonging to the Verbenaceae family. The first objective of this investigation was to study the propagation of fever tea using stem cuttings. The main variables studied were cutting position, rooting media and rooting hormone. The germination requirement of fever tea seed is also not known. Therefore, the second objective was to investigate the ideal seed germination temperature and light combinations. Germination was tested at constant temperature regimes (15, 20, 25 and 30 °C) with a continuous light or dark period and at alternate temperatures of 20/30 °C and 16/8 hour (light/dark) combinations, respectively. For the stem cutting investigation, sampling was done every 5, 10, 15, and 20 days from plant establishment. Apical cuttings took less time to root than basal cuttings regardless of growing medium. Response of cuttings to rooting hormone was growing medium-related. With rooting hormone, it took 10 days to root most of the apical cuttings, whereas basal cuttings showed more roots in 15 to 20 days after plant establishment. Cuttings in sand took 5 days longer to root than in pine bark, regardless of rooting hormone. Therefore, for quicker establishment of fever tea stem cuttings, rooting hormone and pine bark should be used for propagation of both apical and basal cuttings. In the germination investigation, it was found that fever tea seeds are positively photoblastic. Regardless of temperature, seeds failed to germinate in continuous darkness. The germination percentage was improved at continuous or alternating temperatures above 20 °C with continuous light. However, the germination percentage decreased with alternating light and dark treatments.

Germination of Dandelion Seed on a Thermogradient Plate

Fresh and stored dandelion (Taraxacum officinale Weber) seeds were studied to determine the germination response to a range of constant and alternating temperature regimes on thermogradient plates. Germination was initiated over a wide range of temperatures. Maximum germination of fresh seed occurred at an alternating temperature of 20 C for 16 hr and 10 C for 8 hr. Seed stored for 30 days germinated best at 20 C for 16 hr and 15 C for 8 hr. In addition to the shift in germination requirement, dormancy increased during the 30-day storage, especially at −15 C.