Imbibitional Chilling Injury Research Articles

The Seed Coat as a Control of Imbibitional Chilling Injury

The imbibition of pea (Pisum sativum L.) seeds proceeds slowly in cold water, with little effect on subsequent vigor; soybean [Glycine max (L.) Merr.] seeds imbibe cold water rapidly, and suffer significant vigor loss. When the imbibitional rate of peas was increased by nicking the seed coats, the peas became susceptible to chilling injury. Conversely, when the rate of soybean imbibitionwas slowed with a solution of polyethylene glycol (PEG 6000), their susceptibility to imbibitional chilling was considerably lessened. Sensitivity to imbibitional chilling is thus a consequence of the rate of cold water uptake.Cellular damage to cold‐imbibed peas and soybeans was assessed as inability to reduce triphenyl tetrazolium chloride (TTC). Peas showed only a low level of damage when imbibed with intact seed coats at 2 C, but increased damage when imbibed with nicked seed coats. Soybeans, however, showed considerable cellular damage when imbibed intact, and no further damage when imbibed with nicked seed coats. Pea seed coats thus offer considerable protection against rapid imbibition and chilling damage, whereas the soybean seed coat offers little.Soybeans with black‐pigmented seed coats imbibed water more slowly than nonpigmented soybeans. Blackpigmented soybeans also showed less vigor loss following imbibition at 0 C, and exhibited no cellular damage as determined with TTC stain. Vigor of blackpigmented seeds after 23 C imbibition was less than that of nonpigmented, however, due to a slower rate of radicle penetration of the tougher black seed coats.

Imbibitional Chilling Injury in Soybean Axes: Relationship to Stelar Lesions and Seasonal Environments1

AbstractThe increasing use of isolated embryonic axes as experimental tissues for studies on early germination events warrants an evaluation of stress effects during hydration. The objectives were to evaluate embryonic axis growth and stress crack formation in soybean (Glycine max (L.) Merr.) seeds and isolated axes resulting from hydrational stresses of cold temperatures and low tissue moisture. Sensitivity to imbibitional chilling of seeds and isolated axes was evaluated in several cultivars produced in different years at different locations. Germination, seedling growth, and formation of stelar lesions were measured. Isolated axes with an initial moisture content of 6% were injured by imbibition at 5 C as evidenced subsequently by reduced growth at 25 C. Adjustment of axis moisture to 17% before hydration protected against imbibitional chilling injury. Sensitivity to imbibitional chilling was influenced by cultivar and year or location of production. Lesions formed across the stele of hypocotyls during rapid hydration of 6% initial moisture isolated axes at 5 or 25 C but were not observed after hydration of 17% moisture axes or after hydration of intact seeds. The presence of lesions suggests caution when using isolated embryonic axes as experimental tissues.

Relationship of Stelar Lesions to Radicle Growth in Corn Seedlings1

AbstractChilling during imbibition of Zea mays L. kernels resulted in anatomical lesions across the stele of radicles, and subsequently in reduced growth of radicles. The objective was to determine if stelar lesion formation accounted for the radicle growth reduction. Inheritance patterns, source of seedstodrs, maturity of kernels, and surgical treatments of pericarp and endosperm were used to compare lesion occurrence and radicle growth in laboratory evaluations of field‐grown seedstocks. Chilling injury of 5% (low) moisture kernels was measured as radicle growth reduction after a 48 hour hydration treatment at 5 C followed by 4 days at 25 C when compared to Similarly treated controls with 13% moisture kernels. Chilling injury was also measured as stelar lesion formation. In cresses between the sensitive inbred ‘Oh51A’ and the injury resistant inbred ‘B8,’ both radicle growth reduction and stelar lesion formation were receive characters. While the inheritance of either character was not altered substantially by the maternal parent in studies of intact kernels, pericarp damage in chilling sensitive crosses resulted in more severe radicle growth reduction without increasing lesion frequencies. Removal of the endosperm prior to imbibitional chilling resulted in lower lesion frequencies in sensitive inbreds and hybrids. Various sources of the Oh51A inbred had markedly different sensitivities to imbibitional chilling. Maximum sensitivity occurred before kernel maturation. Increasing kernel moisture to 13% before hydration at 5 C reduced or avoided injuries caused by imbibitional chilling of 5% moisture kernels. The embryo, pericarp, and endosperm each influenced the severity of imbibitional chilling injury. While the stelar lesion may contribute to radicle growth reduction, it was not the only factor responsible for imbibitional chilling injury of corn.

Imbibitional Chilling Sensitivity Among Soybean Cultivars1

Fifteen soybean (Glycine max (L.) Merr.) cultivars were screened for sensitivity of embryos to imbitional chilling injury. All were susceptible to injury, but sensitivity varied greatly. Some showed no injury at 7 C while others were injured at 17 C. Embryos of earlier maturing cultivars tended to be more susceptible to imbibitional chilling injury than those of later maturing cultivars. This relationship of time of maturation to chilling sensitivity was confirmed using near‐isogenlc lines of ‘Clark’ soybean, a cultivar possessing various genes that advanced or delayed maturity. Earlier maturing lines were more sensitive to chilling than later maturing lines. Leakage of solutes during imbibition, measured as OD280, was negatively correlated with germination when near.isogenic strains were compared, but was not closely correlated when different cultivars were compared.It is proposed that seed maturation occurring later in the growing season, during periods of relatively low temperature, hardens seeds against chilling injury.

Independence of Imbibitional Chilling Injury and Energy Metabolism in Corn1

Energy metabolism of 5 (low) and 13% (high) moisture Zea mays L. inbred ‘Oh51A’ kernels was measured at 0, 12, 24, and 48 hours at 25 C subsequent to imbibition at 5 C. Radicle growth was measured at 1, 2, 3, and 4 days. The interaction of low kernel moisture with imbibition at 5 C resulted in reduced radicle growth in seedlings. Oxygen uptake of whole kernels after imbibitional chilling was independent of initial kernel moisture. Differences in initial moisture also did not alter ATP levels of embryos and embryonic axes after chilling. ATP increased about 20‐fold and adenylate energy charge of embryos increased from 0.2 to 0.8 during hydration at 5 C irrespective of initial moisture content. Mitochondria isolated from embryos of low moistttre kernels exhibited slightly higher respiratory rates 24 hours after cold imbibition but not at other sampling times. ADP/O .ratios and respiratory control ratios (succinate substrate) of isolated mitochondria were not altered by initial kernel moisture. A disruption of energy metabolism is not a primary cause of kernel moisture‐mediated imbibitional chilling injury.

Imbibitional Chilling Injury in Zea mays L. Altered by Initial Kernel Moisture and Maternal Parent1

The differential seedling growth of corn (Zea mays L.) hybrids after seeding at cold temperatures led to an evaluation of the effect of initial kernel moisture and parental lines on germination and seedling growth after cold imbibition. Low‐ and high‐moisture kernels were imbibed 0 to 21 days at 5C. Effects of cold during germination were evaluated by survival and growth of seedlings at 25C.Imbibition of low‐moisture (6%) kernels at 5C resulted in aborted radicles, proliferation of seminal roots, and delayed seedling growth. For certain inbreds and crosses, prolonged exposure to 5C resulted in reduced survival. Sensitivity to imbibitional chilling was partially or totally reversed when initial kernel moisture was 13 or 16%. Cornell M‐3 was sensitive to chilling while Pennsylvania 290 was relatively tolerant, but certain parental lines of both hybrids were sensitive. Sensitivity of reciprocal hybrids indicated maternal effects.