Heat stress during seed development affects forage brassica (Brassica napus L.) seed quality

Abstract

In two consecutive seasons, forage rape (Brassica napus L.) plants were exposed to short periods (240°C hr) of heat stress (30°C day/25°C night) during seed filling (80% seed moisture content = S1), at physiological maturity (50% seed moisture content = S2) and at both S1 plus S2 (=S3) in a Biotron before being returned to the field until seed harvest. Seeds were hand harvested at 14% seed moisture content and their quality assessed by measuring germination, seed vigour (using the accelerated ageing and conductivity tests) and seed mass (as determined by thousand seed weight). Heat stress at both S1 and S2 caused a small (<10%) but significant reduction in germination in both seasons. There was a significant heat stress timing interaction in the first but not the second season. Reductions in germination were a result of increased abnormal seedling production not seed death. All three heat stress treatments significantly reduced seed vigour, with S3>S2>S1. Seed mass was reduced by heat stress at S1 but not at S2. Variable seed vigour in high‐germinating New Zealand‐produced forage rapeseed lots is most likely explained by short periods of heat stress during seed development.

Parental Environmental Effects on Seed Quality and Germination Response to Temperature of Andropogon gerardii

“…The variation observed in maximum seed germination, and the seed germination rate between parental environments (PEs) suggests that sub-and supra-optimal growth temperatures during seed development could limit the rate of re-establishment of big bluestem under field conditions [21]. Rashid et al [19] and Hampton et al [1] explained that reductions in seed germination responses and seed weight are mainly due to decreased growth rates and a shortening of the seed filling period under elevated growth temperatures. The strong and positive correlation between maximum seed germination and seed weight and seed reserves indicated variations in seed quality parameters [46] that have usually been ascribed to changes in the parent environment, which was reflected in maximum seed germination (MSG).…”

“…Seed germination studies have evaluated the percentage of germination, the germination rate, and three cardinal temperatures (the minimum, maximum, and optimum) that govern the temperature range across which germination can occur. These germination matrices are also useful in evaluating the impacts of maternal environmental conditions on seed quality traits [1,6,10,19]. Since temperature and CO 2 fluctuations are anticipated influencing crop productivity under natural settings, evaluation of seed germination characteristics at a range of temperature regimes would provide insight into the adaptability of big bluestem and a possible link to maternal environments.Big bluestem (Andropogon gerardii Vitman) is a dominant perennial warm-season C 4 grass species that contribute ≈80% of the biomass in the natural and managed grasslands of the United States [20].…”

Drought or/and Heat-Stress Effects on Seed Filling in Food Crops: Impacts on Functional Biochemistry, Seed Yields, and Nutritional Quality

“…Exposure to heat stress during pod and seed filling stages results in a substantial decrease in economic yield of crop plants by reduction in seed weight. Decline in seed weight and seed number due to high temperatures has been reported in several crops including legumes ( Prasad et al, 2000 ; Tsukaguchi et al, 2003 ; Devasirvatham et al, 2010 ), cereals ( Djanaguiraman et al, 2010 ) and others ( Rashid et al, 2017 ). Sustaining grain weight in heat stress conditions during seed filling stage is considered a part of heat stress tolerance mechanism ( Tyagi et al, 2003 ; Hasanuzzaman et al, 2013 ).…”

“…While these two stresses affect the seed filling differently, each one leads to reduced seed size due to reduction in the cell number in endosperm/cotyledons, inhibitions or acceleration of seed filling rate and various biochemical processes, as in wheat ( Nicolas et al, 1985 ) and maize ( Monjardino et al, 2005 ). Variations may also exist in the relative composition of seed reserves in response to either of these stresses, nevertheless, in general, seed quality was adversely affected by both the stresses ( Khan et al, 2004 ; Spiertz et al, 2006 ; Thuzar et al, 2010 ; Krishnan et al, 2011 ; Rashid et al, 2017 ).…”

Sanitary and physiological quality of ‘purple’ corn (Zea mays L.) seeds submitted to thermotherapy

“…2). Probably, thermal stress altered the balance between the production of reactive oxygen species (ROS) and ROS elimination enzymes, partially reducing the metabolic activity needed to continue and stimulate normal root growth (RASHID et al, 2017).…”