Parameters of Physical and Physiological Quality in Seed Produced during High Season for Different Periods of Development

Objective: To evaluate the quality of the seeds of tomato fruits (Solanum lycopersicum Mill.) produced in high temperture (HT) during different phases of development. Design/Methodology/Approach: Seeds of the Moneymaker variety were planted in a ventilated greenhouse (control treatment, CT) with maximum mean temperature (MMT) of 31.5 °C. A second greenhouse with artificial heating (MMT of 36.5 ºC) was used for the HT treatments. When anthesis began from the fourth floral cluster, seven treatments were established: T1) fruits growing permanently in the CT; T2) fruits transferred to HT between five and 12 days after anthesis (daa); T3) fruits growing in HT from 12 to 24 daa; T4) 24-36 daa in HT; T5) 36-48 daa in HT; T6) 48-60 daa in HT; T7) from 60 daa to maturity in HT. Results: The weight of one thousand seeds (SW) had a positive correlation with the length of seed (R=0.83*), indicating that the increase in SW was primarily determined by an increase in length. The vigor of the seed was measured by the germination after accelerated ageing (GAA); thus, germination and vigor are positively correlated with seed respiration during germination (0.62* and 0.81*, respectively). Study Limitations/Implications: HT impacting on the second phase of seed development could decrease both the physical and the physiological quality of tomato seeds. Findings/Conclusions: The seeds produced by T7 had lower SW (2.99 g). T5 caused lower amount of seeds per fruit (120), germination (79.4 %) and GAA (39.5 %).

Using seed respiration as a tool for calculating optimal soaking times for ‘on-farm’ seed priming of barley (Hordeum vulgare)

A low-cost technique named ‘on-farm’ seed priming is increasingly being recognized as an effective approach to maximize crop establishment. It consists of anaerobically soaking seeds in water before sowing resulting in rapid and uniform germination, and enhanced seedling vigour. The extent of these benefits depends on the soaking time. The current determination of optimal soaking time by germination assays and mini-plot trials is resource-intensive, as it is species/genotype-specific. This study aimed to determine the potential of the seed respiration rate (an indicator of metabolic activity) and seed morphological changes during barley priming as predictors of the priming benefits and, thus, facilitate the determination of optimal soaking times. A series of germination tests revealed that the germination rate is mostly attributable to the rapid hydration of embryo tissues, as the highest gains in the germination rate occurred before the resumption of respiration. Germination uniformity, however, was not significantly improved until seeds were primed for at least 8 h, that is, after a first respiration burst was initiated. The maximum seedling vigour was attained when the priming was stopped just before the beginning of the differentiation of embryonic axes (20 h) after which vigour began to decrease (‘over-priming’). The onset of embryonic axis elongation was preceded by a second respiration burst, which can be used as a marker for priming optimization. Thus, monitoring of seed respiration provides a rapid and inexpensive alternative to the current practice. The method could be carried out by agricultural institutions to provide recommended optimal soaking times for the common barley varieties within a specific region.

Temperature and Imbibition Influence Serianthes Seed Germination Behavior

The direct role of physical dormancy in delaying germination of Serianthes grandiflora Bentham, Serianthes kanehirae Fosberg, and Serianthes nelsonii Merrill seeds has not been adequately studied, nor has the role of temperature on germination behaviors. Imbibition testing indicated seeds with scarified testa absorbed water for the duration of a 24 h imbibition period, but seeds with an intact testa stopped absorbing water after 1 h. The behavior of S. nelsonii seeds most closely matched those of S. kanehirae, with the pattern of water absorption for S. grandiflora seeds deviating from that for the other species. Scarified seeds germinated readily, with initial germination occurring by 50 h for S. nelsonii and 90 hr for the other species, and maximum germination of 80% to 90% occurring by 60 h for S. nelsonii and 100 h for the other species. Predicted optimum temperature based on a fitted quadratic model was 26 °C for S. nelsonii, 23 °C for S. grandiflora, and 22 °C for S. kanehirae. Seed respiration increased within 3 h of imbibition for scarified seeds and continued to increase in a linear pattern. The linear slope was greatest for S. nelsonii, intermediate for S. grandiflora, and least for S. kanehirae, but ultimate respiration was greatest for S. kanehirae seeds. Seed respiration was so limited for un-scarified seeds that the instrument was unable to quantify any carbon dioxide efflux. Physical dormancy in seeds of these Serianthes species is a powerful trait that spreads out the timing of seedling emergence in natural settings and controls imbibition and germination speed in managed nurseries.

INFLUENCE OF SOYBEAN SEED MOISTURE CONTENT IN THE RESPONSE TO SEED TREATMENT IN SOYBEAN

Seed treatment (ST) is an important practice for soybean crop. This research had the objective to evaluate the influence of seed moisture content in the response to different spray volumes (SV) used for seed treatment in soybean, considering effects on seed physiological quality. Three seed lots with distinct moistures were used: 7.2%, 10.1% and 13.0%. Untreated seeds (control) and three SV were tested: 8, 13 and 18 mL kg-1. All lots received the same treatment combination, containing insecticide, fungicide, fertilizer and biostimulant. This combination represented 8 mL kg-1 of SV; the doses of 13 and 18 mL kg-1 were obtained by adding 5 and 10 mL kg-1 of water, respectively. Evaluations of seed physiological quality consisted of electrical conductivity, seed respiration, germination and vigor tests. Results of all tests demonstrates that low-moisture soybean seeds (7.2%) are negatively affected by seed treatment within an SV range of 8 to 18 mL kg-1, while untreated seeds with equal moisture are not affected. Oppositely, high-moisture seeds (13.0%) are not affected by the SV tested, while intermediate-moisture seeds (10.1%) are affected by the higher SV. This result highlights seed moisture as a key parameter to be managed before soybean ST, aiming to maintain a high physiological quality.

Hypoxia in the grape berry linked to mesocarp cell death: the role of seed respiration and lenticels on the berry pedicel

Mesocarp cell death (CD) during ripening is common in berries of seeded Vitis vinifera L wine cultivars. We examined if hypoxia within berries is linked to CD. Internal oxygen concentration ([O2]) across the mesocarp was measured in berries from Chardonnay and Shiraz, both seeded, and Ruby Seedless, using an oxygen micro-sensor. Steep [O2] gradients were observed across the skin and [O2] decreased toward the middle of the mesocarp. As ripening progressed the minimum [O2] approached zero in the seeded cultivars and correlated to CD. Seed respiration was a large proportion of total berry respiration early in ripening but did not account for O2 deficiency late in ripening. [O2] increased towards the central axis corresponding to the presence of air spaces visualised using x-ray microCT. These connect to lenticels on the pedicel that were critical for berry O2 uptake as a function of temperature, and when blocked caused anoxia in the berry, ethanol accumulation and CD. Lenticel area on Chardonnay pedicels was higher than that for Shiraz probably accounting for the lower sensitivity of Chardonnay berry CD to high temperatures. The implications of hypoxia in grape berries are discussed in terms of its role in ripening and berry water relations.HighlightGrape berry internal oxygen concentration is dependent upon lenticels on the pedicel and cultivar differences in lenticels may account for temperature sensitivity of cell death in the mesocarp.