Two cultivars of sweetpotato, `Commensal' and `Salyboro', were subjected to salt stress using axillary bud cultures. The salt levels ranged from 0 to 10 g·L-1. After the initial experiments, levels of calcium in the medium were changed from 3 mm in the MS medium to 1.5, 6, and 12 mm. After 10 weeks of growth, plantlet shoot height, dry weight, number of nodes, levels of proline, soluble carbohydrate, and protein were measured. `Commensal' was tolerant to salt levels up to 4 g·L-1, but `Salyboro' was sensitive to concentrations of salt even at lower concentrations as evidenced by the growth and dry weight. Proline accumulation was higher in the shoot than in the root. The protein: carbohydrate ratios did not change much in `Commensal', but levels of carbohydrates increased in `Salyboro'. Reduction in calcium levels had a synergistic affect on salt-stressed cultivars. Enhanced levels of calcium reduced the inhibitory affects of salt stress. This was more pronounced in `Salyboro', which was susceptible. Proline levels were higher in plants subjected to salt stress and higher levels of calcium than controls, but lower than the plants subjected to salt stress. These and other metabolic changes suggest that calcium can reduce the adverse affects of salt stress in these two sweetpotato cultivars.
Abstract
One-month-old seedlings of 20 entries of tomato (Lycopersicon esculentum Mill.) were subjected to flooding for 3 days, or drenched with ethanol or (2-chloroethyl)phosphonic acid (ethephon) solution. Flooding reduced stem growth and leaf chlorophyll content of thelower leaves and promoted epinastic curvature of leaf petiole and adventitious roots. Application of ethephon elicited a response similar to that of flooding. No prominent morphological and physiological changes were observed from ethanol application. Flooded plants show increases in their endogenous free proline pool, which can be reduced by the withdrawal of flooding. Flooded L-123 plants, the most tolerant entry, accumulated the least free proline among three entries tested. Proline level appeared to indicate the intensity of oxygen deficiency during soil flooding by reflecting oxygen supply, and could serve as in indicator in relating plant injury to flooded conditions. The tolerance of L-123 to soil flooding, at least in part, depends on its ability to transport oxygen from the aerial part to the root.
Abstract
The effects of water deficits were examined on osmotic regulation of germinating seedlings of tomato (Lycopersicon esculentum Mill cv. Campbell 1327). Seed were germinated in aerated water and then grown for an additional 2 days in Petri dishes. The germinated seeds were then transferred to water potentials of 0 to −6 bars in 2-bar increments. Mannitol and water was used to obtain the desired water potential of the media. Water relations, growth rates and reducing sugars, non-reducing sugars, amino acids, proline, nitrates, phosphates, potassium, and electrical conductivity were determined for roots and shoots at different water stresses. As water stress increased, osmotic adjustment occurred in the roots which accounted for the maintenance of turgor and growth. During the same period, little adjustment occurred in the shoots and consequently growth decreased. Turgor potential was highly correlated with growth rates for both plant parts. All solutes measured, except proline, generally increased in the roots and decreased in the shoots as water stress increased. Proline increased in both plant parts during the same period. Thus, solute regulation occurred during water deficits. Osmotic regulation in germinating tomato seedlings appears to be an adaptive feature during periods of water stress.
Abstract
Protein amino acids in leaves of Phytophthora spp.-infested or noninfested plants were not affected measurably. Leaves from plants supplied with low soil oxygen levels contained significantly less protein amino acids: lysine, histidine, aspartic acid, threonine, serine, glutamic acid, glycine, alanine, valine, isoleucine, leucine, tyrosine, and phenylalanine but more arginine than analogous leaves of plants supplied with normal soil oxygen concn.
The leaves of Phytophthora-infested plants contained significantly lower concn of nonprotein amino acids: threonine, glycine, alanine, cystine, valine, methionine, isoleucine, leucine, tyrosine, and phenylalanine but higher concn of arginine and aspartic and glutamic acids. The nonprotein amino acids: lysine, arginine, aspartic acid, and pro line were higher, while threonine and glutamic acid were lower, in seedling leaves supplied with low soil oxygen than those in leaves on plants supplied with normal soil oxygen.
The protein and nonprotein proline, and the sum of nonprotein amino acids increased in leaves of noninfested plants, while decreasing in leaves of infested plants, with a decreasing level of soil oxygen to roots.
Substantive amounts of protein amino acids found in citrus seedling leaves were glutamic acid, aspartic acid, proline, leucine, and arginine; those of nonprotein amino acids were proline, arginine, serine, lysine, and aspartic acid. These amounts represent, respectively, 50 and 90% of the sum.
Abstract
Water-stressed young, potted citrus seedlings and budded trees on different rootstocks were tested for freeze avoidance and tolerance. Water stress increased the supercooling of cold-sensitive citrus seedlings in freezeavoidance tests and increased the cold hardiness of grapefruit and orange trees in freeze-tolerance tests. Water stress was most effective in reducing injury during freezes above −6.7°C. Temperatures below −6.7° resulted in complete kill regardless of −25 bars water stress in the leaves. Tissue analyses showed increased in proline accompanying increases in sugars during forced dehydration of citrus leaves.
Abstract
Chlorotic foliage of Euphorbia pulcherrima did not contain substantially higher levels of free amino acids than normal non-chlormequat treated foliage, and in some cases levels were lower indicating inhibition rather than protein degradation.
Free amino acids detected and measured in µ/g fresh wt included glycine, alanine, valine, leucine, isoleucine, serine, threonine, aspartic acid, glutamic acid, glutamine, lysine, arginine, histidine, cystine, proline and phenylalanine.
The high fertilizer rates stimulated chlorophyll regeneration after damage from phytotoxic spray application of chlormequat and was closely correlated with amino acids im portant in N metabolism.
The possibility of osmotic adjustment to salinity in Jojoba was studied in a sand culture system. After being stablished, 2 WKs old seedlings were exposed to 1/2 strength hoagland's solution plus NaCl salt to make up -0.7., -0.4, -0.6, -0.8, & -1 MPa. Shoot & leaf elongation, components of Ψleaf, proline accumulation, & inorganic salts were determined every 24 hour for 9 days. Shoot & leaf length were reduced at -0.8 and -0.4 MPa respectively. Osmotic adjustment occured only above -0.8 MPa at the rate of 0.21 If MPa/day. Total inorganic salts in whole plant increased with a decrease in solution Ψw. However, above -0.8 MPa excess Na & Cl ions were excluded from the leaves & accumulated within the roots, while K/Na ratio remained higher above -1 MPa. The selective uptake of K ions seems a possible mechanism for osmotic adjustment in Jojoba. Accumulation of Na & Cl ions under -1 MPa correlated with occasional pale green discoloration & tip-burn of leaves. Although the accumulation of proline was considerable at & below -0.8 MPa, but did not play a significant role in osmoregulation.
Axillary bud cultures of sweetpotato Ipomoea batatus L. [cultivars comensal and salyboro] were propagated in vitro. Nodal cultures of these were grown at different temperatures ranging from 10 °C to 30 °C at 5 °C intervals from the time of axillary bud transfer to 10 weeks of growth in a controlled growth chamber. After 10 weeks of growth, morphological and physiological parameters were measured including shoot height, number of nodes and branches, levels of proline, soluble carbohydrate and protein. There was not much difference in the cultures grown at 25 and 30 °C but temperatures lower than 25 °C were inhibitory to both cultivars, though the effects were more pronounced in salyboro than comensal. Salyboro grew slower and exhibited leaf discoloration, weak stems, and poor root growth. Proline levels increased in both cultivars and the increase was higher in shoot than root due to low temperature stress. Soluble carbohydrates and proteins increased in comensal, maintaining the carbohydrate protein ratio, but decreased in salyboro. The results suggest that the cultivar comensal may tolerate cooler temperatures and the cultivar salyboro is susceptible to them.
Abstract
There was an accumulation of total free amino acids (calculated as the sum of the individual amino acids) in corollas from cut ‘Sonia’ roses (Rosa hybrida) stored at 2C (cold-stored flowers) but not in those kept at 20C (control flowers). In cold-stored flowers, senescence was retarded, as indicated by only a slight opening of the corolla and no subsequent petal abscission. Hence, there appeared to be no direct correlation between senescence of cut roses and accumulation of total amino acids in corollas; neither was there a relationship between individual or total free amino acids and protease activity in the corollas from either cold-stored or control flowers. Changes in the contents of all free amino acids, except alanine and lysine, were affected by cold storage. The effect on aspartic acid was statistically significant, but not spectacular. Cold storage delayed the decrease in contents of glutamic acid, asparagine, tyrosine, glycine, leucine, isoleucine and valine, and prevented accumulation of phenylalanine, proline, and histidine. We detected only one theoretically expected interconversion between two amino acids; i.e., glutamic acid to proline, that occurred in corollas from control flowers during the first 6 days of storage. We suggest that the patterns of changes in the contents of tyrosine, valine, isoleucine (or isoleucine plus leucine), and phenylalanine are not restricted to the cultivar Sonia.
Physiological responses to salinity and relative salt tolerance of six C4 turfgrasses were investigated. Grasses were grown in solution culture containing 1, 100, 200, 300, and 400 mm NaCl. Salinity tolerance was assessed according to reduction in relative shoot growth and turf quality with increased salinity. Manilagrass cv. Matrella (FC13521) (Zoysia matrella (L.) Merr.), seashore paspalum (Hawaii selection) (Paspalum vaginatum Swartz), and St. Augustinegrass (Hawaii selection) (Stenotaphrum secundatum Walt.) were tolerant, shoot growth being reduced 50% at ≈400 mm salinity. Bermudagrass cv. Tifway (Cynodon dactylon × C. transvaalensis Burtt-Davey) was intermediate in tolerance, shoot growth being reduced 50% at ≈270 mm salinity. Japanese lawngrass cv. Korean common (Zoysia japonica Steud) was salt-sensitive, while centipedegrass (common) (Eremochloa ophiuroides (Munro) Hack.) was very salt-sensitive, with total shoot mortality occurring at ≈230 and 170 mm salinity, respectively. Salinity tolerance was associated with exclusion of Na+ and Cl- from shoots, a process aided by leaf salt glands in manilagrass and bermudagrass. Shoot Na+ and Cl- levels were high at low (100 to 200 mm) salinity in centipedegrass and Japanese lawngrass resulting in leaf burn and shoot die-back. Levels of glycinebetaine and proline, proposed cytoplasmic compatible solutes, increased with increased salinity in the shoots of all grasses except centipedegrass, with tissue water levels reaching 107 and 96 mm at 400 mm salinity in bermudagrass and manilagrass, respectively. Glycinebetaine and proline may make a significant contribution to cytoplasmic osmotic adjustment under salinity in all grasses except centipedegrass.