Sunflower (Helianthus annuus L.) seeds progressively lost their ability to germinate at 25°C, the optimal temperature for germination, after accelerated aging was carried out at 45°C (a temperature too high to permit germination) in water or at 76 or 100% relative humidity (RH). The deleterious effects of the high-temperature treatment increased with increasing seed moisture content. Incubation of seeds at 45°C in water resulted in electrolyte leakage, which indicated a loss of membrane integrity. A relationship between leakage and loss of seed viability could not be assumed, since no increase in electrolyte efflux occurred after aging al 100% RH. Accelerated aging induced accumulation of malondialdehyde, suggesting that seed deterioration was associated with lipid peroxidation. However, there was no direct relationship between lipid peroxidation and deterioration in membrane integrity. Loss of seed viability was also associated with a decrease in superoxide dismutase, catalase and glutathione reductase activities. Finally, the results obtained suggest that sunflower seed deterioration during accelerated aging is closely related to a decrease in the activities of detoxifying enzymes and to lipid peroxidation.

Changes in malondialdehyde content and in superoxide dismutase, catalase and glutathione reductase activities in sunflower seeds as related to deterioration during accelerated aging

In a laboratory study, indica and japonica rice (Oryza sativa L.) seeds were exposed to thermal hardening (heating followed by chilling followed by heating; chilling followed by heating followed by chilling; heating followed by chilling or chilling followed by heating). In indica rice, heating followed by chilling followed by heating resulted in decreased mean germination time, time to start germination, electrical conductivity of seed leachates, and time to 50% germination, as well as increased germination index, energy of germination, radicle and plumule length, root length, root/shoot ratio, root fresh and dry weight, radicle and plumule growth rate, and shoot fresh weight. In japonica rice, chilling followed by heating followed by chilling performed better than all other treatments, including control.

( Managing editor: Ping HE)

https://onlinelibrary.wiley.com/doi/pdf/10.1111/j.1744-7909.2005.00031.x

Thermal Hardening: A New Seed Vigor Enhancement Tool in Rice

Preplant Physiological Seed Conditioning

The optimum temperature for maize germination is between 25 and 28 °C. Poor and erratic germination at suboptimal temperature is the most important hindrance in its early sowing. This study was conducted to induce chilling tolerance in hybrid maize (Zea mays L.) by seed priming with salicylic acid (SA) and to unravel the background biochemical basis. For seed priming, maize hybrid (Hycorn 8288) seeds were soaked in 50, 100 and 150 ppm (mg l -1 ) aerated solutions of SA for 24 h and were dried back. Treated and untreated seeds were sown at 27 °C (optimal temperature) and at 15 °C (chilling stress) under controlled conditions. Performance of maize seedlings was hampered under chilling stress. But seed priming with SA improved the seedling emergence, root and shoot length, seedling fresh and dry weights, and leaf and root score considerably compared with control both at optimal and chilling temperatures. However, priming in 50 mg l -1 SA solution was more effective, followed by priming in 100 mg l -1 SA solution. Seed priming with SA improved the chilling tolerance in hybrid maize mainly by the activation of antioxidants (including catalase, superoxide dismutase and ascorbate peroxidase). Moreover, maintenance of high tissue water contents and reduced membrane permeability also contributed towards chilling tolerance.

Chilling Tolerance in Hybrid Maize Induced by Seed Priming with Salicylic Acid

In rice-wheat systems, late sowing of wheat is the major reason of low yield. This yield reduction is principally due to lower and erratic germination, and poor crop establishment because of low temperature prevailing. The present study was conducted to explore the possibility of improving late sown wheat performance by seed priming techniques. Seed priming strategies were: on-farm seed priming, hydropriming for 24 h, seed hardening for 12 h and osmohardening with KCl or CaCl 2 for 12 h. Seed priming improved emergence, stand establishment, tiller numbers, allometry, grain and straw yield, and harvest index. However, seed priming techniques did not affect plant height, number of spikelets, number of grains and 1000 grain weight. Osmohardening with CaCl 2 gave more grain and straw yield and harvest index compared with control and other priming treatments, followed by osmohardening with KCl and on-farm seed priming. Improved yield was attributed principally to better stand establishment and improved number of fertile tillers. Seed priming techniques can be effectively used to improve the performance of late sown wheat.

Seed Priming Enhances the Performance of Late Sown Wheat (Triticum aestivum L.) by Improving Chilling Tolerance

The Effect of Low Temperature Pre-Sowing Treatment on the Germination Performance and Membrane Integrity of Artificially Aged Tomato Seeds

Osmotic pre-sowing treatments and nucleic acid accumulation in tomato seeds (Lycopersicon lycopersicum).

Extensive accumulation of nucleic acid may be one of the factors mvolved in the acceleration of tomato seed germination by osmotic presowing treatment The experiments reported here were designed to characterize the changes in the major nucleic acids during osmotic pretreatment and subsequent germination Polyacrylamide gel electrophoresis showed that ribosomal RNA comprised the major part of this net synthesis, but it was more difficult to ascertain whether or not there was a proportional increase in sRNA, as part of the latter peak may comprise comigrating fragments of degraded rRNA The mass ratio of 25S: 18S rRNAs extracted from dry seeds was near unity, while during normal germination and during pretreatment this ratio increased to about 1-9:1, close to the theoretical ratio assuming 25S and 18S rRNAs occur in equimolar proportions This leads to the speculation that replacement of old ribosomes may occur during early germination and pretreatment, although this would not account for all the synthetic activity observed during the latter process Use of the diphenylamine colour reaction showed that no increase in DNA results from pretreatment and that the onset of the first S-phase during subsequent germination of pretreated seeds was commensurate with the advancement of the time to 50% germination

P. Coolbear

Papers

The Effect of Low Temperature Pre-Sowing Treatment on the Germination Performance and Membrane Integrity of Artificially Aged Tomato Seeds

Osmotic pre-sowing treatments and nucleic acid accumulation in tomato seeds (Lycopersicon lycopersicum).

Studies on the Changes in the Major Nucleic Acid Components of Tomato Seeds (Lycopersicon esculentum Mill.) Resulting from Osmotic Presowing Treatment

Changes in the Membrane Phospholipid Composition of Tomato Seeds accompanying Loss of Germination Capacity caused by Controlled Deterioration

A Comparison of Changes in the Germination Responses and Phospholipid Composition of Naturally and Artificially Aged Tomato Seeds