Ability Of Seedlings Research Articles

СОСТОЯНИЕ ХВОЙНЫХ ИНТРОДУЦЕНТОВ В Г. НУР-СУЛТАНА

The article presents observational data on the survival, preservation and growth of introduced tree species created in the interstrip spaces of the green zone of the city of Nur-Sultan. The greatest preservation is characterized by Siberian spruce (Piceaobovata Ledeb.) (76.8%) and blue spruce (Piceapungens Engelm.) (58,9%). Black spruce (Piceamariana Mill.) and Siberian larch (Larixsibirica Ledeb.) have a preservation rate of an average of 44.5%. The lowest survival rate and preservation (16.4%) is distinguished by Siberian fi r (Abiessibirica Ledeb.). When comparing the method of planting forest crops with planting the material with an open and closed root system, it was revealed that the survival ability and preservation of seedlings with ORS was slightly higher than that of seedlings with CRS. The average survival ability of seedlings with ORS was 58.1%, for seedlings with CRS – 53.7%. Plants height corresponds to the biological characteristics of woody species. The highest average height was for Piceamariana Mill (184.1 cm), the smallest average height was for Piceaengelmannii Parry ex Engelm (143.4 cm). The most acclimatized species of woody plants – Piceaobovata Ledeb., Piceapungens Engelm. and Piceamariana Mill – have been identifi ed. These trees have a high capacity for survival, stable growth and decorative effect. These coniferous plants can be used to create green areas of settlements in Kazakhstan, similar in soil and climatic conditions to the city of Nur-Sultan.

Influence of soil characteristics on physiological and growth responses of Cytharexyllum myrianthum Cham. (Verbenaceae) to flooding

The success of watershed riparian forest restoration programs can be affected by the selection of plant species tolerant to flooding and soil types that occur along water courses. We evaluated physiological and growth responses of Cytharexyllum myrianthum seedlings to flooding in three different soil types representative of the Almada River Watershed (ARW), southern Bahia, Brazil. The soils selected, based on the relative abundance and importance in the ARW, were: Luvisol, Argisol, and Spodosol. After 35 days of flooding, the Argisol had the lowest and the Spodosol had the highest reduction–oxidation (redox) potential (Eh). After 35 days of flooding, the Luvisol had higher pH and electrical conductivity (Ec) than the other soils. Stomatal conductance (gs) and net photosynthesis (A) significantly declined in all soil types after 7 days of flooding. After that period, morphological changes characteristic of flood-tolerant plants, such as lenticel hypertrophy and adventitious root formation, were observed in all flooded plants. Following the morphological changes, gs and A in flooded plants increased to values close to those of the non-flooded plants. The highest relative growth rates based on mass (RGRm) and net assimilation rates (NAR) for the non-flooded plants were observed in the Argisol. After 35 days of flooding, no significant differences in RGRm or NAR were observed between non-flooded and flooded plants in the Luvisol, but large significant decreases in RGRm and NAR were observed for the flooded plants in the Spodosol. Our results demonstrated that the ability of seedlings of the same species to acclimate to flooded soil conditions differs among soil types. Therefore, the characteristics of soils present in a watershed should be considered when selecting tree species for the reforestation of riparian forests.

Föhrenverjüngung: Plastizität und Akklimatisation in einem trockeneren Klima

Pine regeneration: plasticity and acclimation in a dryer climate Increasing summer drought might limit the natural regeneration of Scots pine stands at low elevations of the Rhone valley. Common garden experiments at the forest-steppe ecotone have shown that emergence and establishment of Scots pine primarily depend on spring precipitation and, to a minor degree, on summer drought and rising temperatures. Scots pine seedlings acclimated rapidly to drought periods by favouring root to shoot growth. In the second year, the saplings were already adapted to drought so that most of them survived an extended spring and summer drought, as recorded at Sion twelve times during the last 154 years. Only an extreme summer drought – no water from June to September – killed 14.7% of the Scots pine saplings. Surprisingly, they were even able to acclimate to such extreme drought events: after the same extreme summer drought in the third year, mortality dropped below 5%. In general, the Scots pine was very plastic, i.e. seedlings and saplings changed their phenotype depending on environmental conditions. But we also found genetic adaptation: Scots pine originating from regions with pronounced summer drought, including populations from lower elevations in the Rhone valley, produced more biomass than those from moister regions in all treatment combinations. Black pine reacted similarly to the treatments like Scots pine, but it grew faster and more saplings survived the first extreme summer drought. These results show that Scots pine from low elevations of the Rhone valley is one of the most drought-tolerant provenances in Europe. Thanks to its high phenotypic plasticity and the ability of seedlings and saplings to acclimate to drought on a short time scale, natural regeneration of Scot pine at low elevations of the Rhone valley is likely to occur also under future conditions, but maybe less frequent than today.

Functional Responses of Woody Prosopis caldenia Seedlings to Drought and Livestock Grazing in Semiarid Rangelands of Argentina

In the semiarid rangelands of Central Argentina overgrazing and drought alter the competitive balance between woody and herbaceous vegetation, favoring an increase in Prosopis caldenia. The objective of this study was to evaluate the effect of competition in perennial grasses and water stress on the relative growth rate (RGR) and related functional attributes of P. caldenia seedlings in sites with different grazing histories: a site exposed to long term (40 or more years) continuous grazing by cattle (grazed experimental site), and a long-term (around 30 years) exclosure (ungrazed experimental site). The total average RGR of the seedlings that grew in the grazed site was significantly higher, whereas the additional water supply favored those seedlings that grew in the ungrazed site. Significant relationships existed between the RGR and all the attributes measured, except in the ungrazed site where only those attributes related to leaf traits were correlated with the RGR. The above- and below-ground biomass of perennial grasses negatively affected the RGR of the P. caldenia seedlings in both experimental sites and soil moisture favored the RGR of the seedlings in the ungrazed site. Our work reveals the ability of seedlings of P. caldenia to take advantage of changes in environmental conditions, such as the release of resources due to overgrazing and to increase its RGR, which ensures its establishment.

Effects of X-rays on seed germination and growth of Scots pine (Pinus silvestris L.) seedlings of different provenience

The effect of ionizing radiation on germination of seed and growth of seedlings of Scots pine was investigated. Higher radioresistance of seed originating from the highland region was established. No difference was found in the investigated seed samples in the content of cysteine and content and composition of the chloroform-soluble fraction. Differences in compounds contained in the chloroform-soluble fraction and in the rate of phosphorus uptake were found in young seedlings of different provenience. They possibly are related to the difference in the ability of seedlings to regenerate the postirradiation damage.

Research on allelopathic effects of phellamurine

Conducted research on new allelochemicals phellamurine extracted from deciduous of Phellodendron amurense, which worked in allelopathy effect to seed germination and growth process of P. amurense and P. chinense in order to interpret the causes of rare seedlings of wild populations of P. amurense. Extracted and separated phellamurine from P. amurense deciduous, and treated the seeds of P. amurense and P. chinense in after-ripening stage and germination stage with different concentrations of phellamurine solution, then detection of the seed germination rate, germination index, seedling height, root length and seed vigor index to evaluate the allelopathic effect of phellamurine. The results show that: phellamurine solution at 0.30 g x L(-1) produce significant inhibition to seed after-ripening of P. amurense, and also the solution at 0.15 g x L(-1) produce significant inhibition to seeds germination of P. amurense; the solution at 0.15 g x L(-1) produce significant inhibition to seeds after-ripening and seeds germination of P. chinense, inhibition intensity increased with the concentration and enhanced. For both species, the presence of phellamurine can lower the seed germination rate, extend the germination time, reduce the ability of seedlings to adapt to the environment, thus the phellamurine may be one of the causes of rare seedlings in the wild population of P. amurense.

Seedling Mortality in Quercus Leucotrichophora A. Camus, Pinus Roxburghii D. Don and Shorea Robusta Gaertn Forest of Kumaun Himalaya, India.

The studies on plant demography hold a considerable significance in plant ecology. Natural regeneration of different plant species through seeds depend primarily upon seed production, germination capacity of seeds and successful establishment of seedling. Successful regeneration of tree species might be considered to be a function of three major components; ability to initiate new seedlings, ability of seedlings and saplings to survive and ability of seedlings and saplings to grow. Several environmental stresses are known to affect the seedling growth but water stress isbelieved to be a major one. The canopy density and soil conditions also affect the growth of seedling.This study comprises three study sites located at29o 22’ N latitudes and 79o 29’ E longitudes along an elevation transect of 350 – 2500 m in Kumaun Himalaya. This region has certain characteristic climatic features. Though it falls under sub-tropical latitude, the abrupt rise in mountains creates a temperature comparable to that of a temperate climate. The seedling dynamics were studied at sal forest, banj oak forest and chir pine forest. For the computation of seedling mortalityand other characteristics, 2x2m permanent quadrats wereestablished in sal, chir-pine and banj oak forest. A total of 12 quadrats were placed in the stand (3 quadrats in each site). To record the mortality of the seedlings, all the seedlings of the year 2008 present in twelve quadrats in each forest were tagged. Their mortality was observed monthly from January 2009 – December 2009. Results show that mortality was very low (20%) at sal forest as compared to banj oak forest (25%) and chir pine forest (35%). The chir pine forest was heavily affected by human disturbance. So the seedling population was more affected if compared to two other sites. Since the biotic stress was negligible there was very little mortality during the study period in banj oak and sal forest suggesting that if biotic stress and natural disturbance is minimum, the rapid regeneration of Q. leucotrichophora and S. robusta would be possible.Current study provides information on the seedling dynamics in three forests types in the Kumaun Himalaya. Results show seedling mortality was very low (20%) at sal forest if compared to banj oak forest (25%) and chir pine forest (35%) so the rapid regeneration of Q. leucotrichophora and S. robusta would be possible.

Cytochemical localization of H+-ATPase and sub-cellular variation in mesophyll cells of salt-treated Cyclocarya paliurus seedlings

Cyclocarya paliurus seedlings of three provenances were treated with three levels of salt (0, 51.0 and 85.0 mmol/L NaCl) in a hydroponic system of a phytotron. The ultrastructural distribution of H+-ATPase activity and ultrastructural variation were investigated in mesophyll cells of C. paliurus seedlings after 12 or 20 days of salt treatment. The results showed that under normal growing conditions, H+-ATPase activity was low and localized mainly in the nucleus. After 12 days of salt treatment and an increase in salinity, we found that the greater the H+-ATPase activity, the lighter the damage suffered by mesophyll subcells after 20 days of salt treatment and the stronger the salt-adaptation ability of seedlings. The location of H+-ATPase, largely in the nucleus, indicated that salt-damage suffered by the seedlings was light, whereas its presence, mainly in the vacuoles, showed that salt-damage was more serious. Our preliminary conclusion is that the salt-tolerance level of C. paliurus seedlings for the three kinds of provenances was in the following order, from high to low: Huangshan seedlings from Anhui Province > Kunming seedlings from Yunnan Province > Jiujiang seedlings from Jiangxi Province.

EFFECTS OF DRIP IRRIGATION MODE AND NaCl CONCENTRATION ON GROWTH AND HYDRAULIC CONDUCTANCE OF APPLE SEEDLINGS

Aims Hydraulic conductance, which is characterized by root water uptake and xylem water transport efficiency, is a physiological response of plants to different environmental factors, such as salt-stress and water deficit. However, there is little research on relationships between different drip irrigation modes and hydraulic conductance. Our objectives were to determine 1) the impact on growth and hydraulic conductance of different drip irrigation modes and salinity treatments and 2) the relationship between apple (Malus pumila) seedling growth and hydraulic conductance. Methods The experiment used a NaCl concentration gradient of 0 (CK), 0.2% (S1), 0.3% (S2) and 0.4% (S3) and three drip irrigation modes: alternate partial root zone drip irrigation (ADI, alternate watering on both sides of the root zone), fixed partial root zone drip irrigation (FDI, fixed watering on one side of the root zone) and conventional drip irrigation (CDI, simultaneous watering on both sides of the root-zone). Important findings Drip irrigation modes and NaCl concentration significantly affect apple seedling growth and hydraulic conductance. Dry matter, leaf area, net growth and hydraulic conductance of apple seedlings were significantly inversely related to NaCl concentration under the same drip irrigation treatment. Root hydraulic conductance (Kr) was significantly linearly correlated with total root dry weight, shoot hydraulic conductance (Ksh) and shoot dry weight. Under the same NaCl concentration treatment and compared with CDI, ADI had a water savings of up to 50%, but average root dry weight,shoot dry weight, total dry weight, leaf area, plant net growth and root hydraulic conductance of ADI only decreased by 8.7%, 19.24%, 13.47%, 11.87%, 32.96% and 10.72%, respectively, showing that ADI has an obvious promoting effect on apple seedling growth and hydraulic conductance. Compared with CDI, high NaCl concentrations S2 and S3 led to decreases in Kl+p of ADI of 33.56% and 44.26%, respectively, while the Kr of ADI treatment increased by 1.13% and 10.91%, respectively, indicating that the root hydraulic signal transmission efficiency of ADI treated seedlings, the ability of seedlings to regulate water balance and resistance stability to salt-stress could be enhanced. The growth and hydraulic conductance of ADI were all higher than FDI. Use of ADI not only improved water-saving regulation ability, but also strengthened resistance stability to salt-stress.

Impacts of Cotyledon Removal on Survival of Blackbrush (Coleogyne ramosissima: Rosaceae) Seedlings

Despite the ecological importance of the regeneration stage of plant life histories (Grime 2001), some of the factors affecting seedling survival, including the interaction between seedlings and their herbivores, are not well-understood (Hanley and May 2006). Herbivory is a major cause of seedling mortality for many woody plant species (Hanley 1998; Moles and Westoby 2004; Fenner and Thompson 2005). The ability of seedlings to cope with herbivory is likely affected by seed size, the presence or absence of cotyledons, and the time elapsed since germination (Bonfil 1998). Because seedlings of woody plant species are small, they can suffer high mortality due to herbivory (Kitajima and Augspurger 1989; Howe 1990; Osunkoya et al. 1992; Asquith et al. 1997; Kitajima 2003). Carbohydrate reserves are important for seedling recovery after tissue loss, especially in shaded understories where photosynthesis is limited (McPherson and Williams 1998; Canham et al. 1999). Cotyledons can support energy and nutrient demands of a young seedling either as photosynthetic or reserve organs (Kitajima 2003). Cotyledons have nutritional value, and it is common to find young seedlings in the field with cotyledons that have been partially or completely removed by insects and browsing vertebrates (Smythe 1978). Such removal of cotyledons before development of the first true leaf is usually fatal (Kitajima 2003). However, even after development of the first leaf, cotyledon loss may greatly reduce seedling survival (Kitajima 2003). Using greenhouse experiments, I investigated how the timing of cotyledon damage and variation in its magnitude influencing survival of young blackbrush (Coleogyne ramosissima Torr.) seedlings through simulated cotyledon herbivory. Specifically, I examined whether differences in the ability of 4-month-old Coleogyne seedlings to survive detachment of cotyledons were related to the timing and extent of cotyledon removal in an environmentally controlled greenhouse.

Inhibition and recovery of germination and growing ability of seedlings under and after osmotic stress induced by polyethylene glycol in 8 pea genotypes

Germination and early seedling growth of eight pea genotypes were examined under and soon after different (5%, 10%, 15%, and 20%) PEG treatments. Seeds were germinated on PEG solution for 3 or 6 days and then further germinated and cultured on filter paper moistened by water for 3 and 6 days. The length and fresh weight of shoots and roots of seedlings were measured and used for evaluation of genotypes. Roots were less inhibited by osmotic stress than shoots similarly to other plant species. The variability among the genotypes was the greatest in the case of shoot growth at 5% PEG treatment and in the case of root growth at 15% PEG treatment. Results suggest that growing responses of genotypes after cessation of stress are more suitable for the evaluation of their osmotic tolerance, than their responses expressed during in vitro stress conditions. Genotypes with relatively high or low osmotic stress tolerance, respectively, could be distinguished with 6 days after recovery from 3-day-long 15% PEG treatment concerning the rate of shoot weight to root weight.

Effect of Zinc on Cadmium Toxicity-Induced Oxidative Stress in Winter Wheat Seedlings

ABSTRACT Two hydroponic experiments were conducted to investigate the antioxidant response of winter wheat (Triticum aestivum L.) to cadmium (Cd)-zinc (Zn) interactions, Seedlings of winter wheat (cv. Yuandong 977), were grown in modified Hoagland nutrient solution with the addition of increasing concentrations of Cd (0, 10, 25, 50 μM). In experiment 2, the seedlings of the same cultivar were treated with constant concentration of Cd (25 μM) and varying levels of Zn (0, 1, 10, 50 μM). Hydrogen peroxide (H2O2) and malondialdehyde (MDA) as well as the activities of three antioxidant enzymes, catalase (CAT), guaiacol peroxidase (GPX), ascorbate peroxidase (APX) were monitored to estimate the amount of oxidative stress and the antioxidant ability of seedlings treated with Cd and Zn for 10 days. The results showed that levels of H2O2 and MDA in experiment 1 were significantly increased with increasing Cd concentrations. The data indicated that Cd could induce oxidative stress and lipid peroxidation in the plants. While H2O2 and MDA levels were significantly reduced by addition of Zn in experiment 2, the activities antioxidant enzymes were enhanced. A concentration of 10 μM Zn appeared to be the optimal level in this experiment for seedlings' growth, chlorophyll synthesis and antioxidant status, indicating that Zn alleviated the oxidative stress induced by Cd.

Rapid Plant-Cover Establishment on Gold Mine Tailings in Southern New Zealand: Glasshouse Screening Trials

The use of a short-term vegetation cover to temporarily control the negative environmental effects of inactive tailings ponds is not frequently practiced during operational mining, but could have some merit. This article reports on a glasshouse trial designed to examine some of the issues associated with short-term vegetation: fast germination of a high proportion of seed, the ability of seedlings to survive in unamended substrates, and potentially toxic substrate. Five nonindigenous plant species were tested—barley (Hordeum vulgare), rye corn (Secale cereale), Italian ryegrass (Lolium multiflorum), red clover (Trifolium pratense), and lucerne (Medicago sativa)—in five different types of substrate: unamended tailings, tailings and fertilizer, tailings and greenwaste, biosolid-blend compost, and local topsoil. The nutrient and heavy metal status (As, Cu, Cd, Ni, Pb) of each substrate type was determined. Plant species performance was monitored over 14 wk. Substrate metal concentrations were low except for As, which was elevated in all substrate types. Plants in unamended tailings grew less vigorously than plants in tailings and compost, or in topsoil. Plant performance in tailings and fertiliser was greatly suppressed following a high fertilization rate. Metal uptake in plants was highest for As (0.4–77 mg kg−1 DW) and Cu (5.3–50.3 mg kg−1 DW). Future field trials are necessary to authenticate findings, but barley and rye corn are promising species for a short-term tailings cover.

The trade-off between breaking of dormancy of caryopses and revival ability of young seedlings of wild barley (Hordeum spontaneum)

The relationship between breaking of dormancy of wild barley (Hordeum spontaneum C. Koch) caryopses and revival ability of young seedlings from a long period of desiccation was studied using barley caryopses stored for 2 years at 5°C and freshly harvested caryopses from a semiarid population in Israel. The 2 years of storage at 5°C significantly enhanced the germination percentages, but dramatically decreased the revival ability of the young seedlings from drought stress. There was a negative correlation between the breaking of dormancy of caryopses and revival ability. There were no significant changes in the effects of storage at a high temperature for periods longer than 5 days. The earlier germination occurred, the higher the revival ability of young seedlings from drought. The results suggest that breaking of dormancy might be at the expense of lowering the subsequent revival ability of young seedlings. The general premise is that a trade-off is expected between dormancy release of caryopses and revival ability of seedlings from drought stress, and that a treatment that aims at breaking dormancy must reach some compromise that optimizes the balance between the two traits based on the specific circumstances.Key words: dormancy breaking, caryopses, revival ability, seedlings, Hordeum spontaneum, wild barley.

Root Egress and Field Performance of Actively Growing Betula pendula Container Seedlings

The objective of this study was to evaluate the possibility of enlarging the planting window of container-grown silver birch seedlings from spring and autumn to summer by planting young, actively growing seedlings. For over 3 yrs the study investigated the growth, survival and damage of silver birch seedlings grown in containers and planted at different times during the growing season on 18 sites in fields and forest sites in central Finland. In a pot experiment in the greenhouse, the root-egress ability of seedlings planted at different times during the growing season was monitored. Root egress of seedlings was rapid from the beginning of July to the middle of August. Actively growing seedlings planted in summer on a site suitable for silver birch grew and survived at least as well as seedlings planted in spring during the dormant stage. The risk of drought stress increased when seedlings were planted on easily drying, coarse sandy soils. The risk was also high in soils with high levels of fine soil fractions that become hard when dry and when the dry period continued for several weeks before planting. In conclusion, it is possible to enlarge the planting window of birch seedlings to July and the beginning of August by using actively growing container seedlings.

Can arbuscular mycorrhiza change the effect of root competition between conspecific plants of different ages?

Seedlings and adults of Hypericum perforatum L., common St. Johnis wort, were grown together in an experiment of factorial design, where the presence of root competition and arbuscular mycorrhizal inoculation were used as treatments. There was moderate shoot competition, the intensity of which was not manipulated. To check the response of plants to arbuscular mycorrhiza in noncompetitive conditions, adults and seedlings were also grown singly in pots. Single individuals of seedlings and adults responded positively to mycorrhizal inoculation, with the response of seedlings significantly greater. In the competition experiment the positive effect of mycorrhizal colonization on seedling growth vanished, since with root competition, both mycorrhizal and nonmycorrhizal seedlings were of the same size. Without root competition, the shoots of mycorrhizal adults were much larger than of nonmycorrhizal adults, but under root competition the shoot weight did not differ. Arbuscular mycorrhiza increased the biomass differences between competing seedlings and adults. We did not confirm our hypothesis that mycorrhiza makes competition between seedlings and adults more balanced because of the stronger positive response of seedlings to inoculation. The positive effect of arbuscular mycorrhizae on growth vanishes in more crowded conditions. It was concluded that if mycorrhizal inoculation has age-specific positive effect of seedlings in field conditions, it is more probably due to higher tolerance to abiotic stress than due to higher competitive ability of seedlings.

Sequestration of 137Cs and 90Sr from soil by seedlings of Eucalyptustereticotnis

The ability of seedlings of Eucalyptustereticornis Smith to accumulate 137Cs and 90Sr, characteristic radioisotopes of nuclear fallout, from contaminated growth medium was tested. All seedlings were grown for 3 months in 165 cm3 of sphagnum peat moss–perlite (1:1 v/v) in a growth chamber before treatment with an isotope. After 1 month of exposure, seedlings had accumulated 31.0% of the 137Cs and 11.3% of the 90Sr originally present in the growth medium, with bioconcentration ratios of 54:1 for 137Cs and 13:1 for 90Sr. Accumulation of 137Cs and 90Sr in plant tissue was correlated curvilinearly with increasing time of exposure and with increasing concentration of radioisotope in the growth medium. Because seedlings of E. tereticornis accumulate these radioisotopes rapidly, they may be valuable in remediation of contaminated soils.

Establishment of Native Grass Seedlings along a Topographic/Moisture Gradient in the Nebraska Sandhills

-This study examines the effect of differential survival of seedlings on the distribution of native grasses along topographic gradients in the Nebraska Sandhills. In 1981, seeds of three ridge species (Andropogon hallii, Sorghastrum nutans, Panicum virgatum) were planted into rototilled, irrigated, rototilled and irrigated, or untreated soils on three sites: one ridge site (ridge) and two valley sites (valley and lowland). The three sites represented a gradient of topography and soil moisture-holding capacity. For all species, seedling survival was greatest (86%) in the rototilled and irrigated treatment on the lowland site. No seedlings survived in untreated plots along the gradient. In 1982 and 1983, seeds of a ridge species (Andropogon hallii) and a valley species (Bouteloua gracilis) were planted in replicated ridge and valley plots. Seeds were planted into either untreated plots, or plots where plants received weekly clipping treatments around seedlings. Although clipping significantly increased survival of both species in both sites, it had a significantly greater effect in valley sites. In untreated plots, seedling survival was greatest (20%) in ridge sites in a year of average precipitation (1982) and in valley sites (49%) in a year that was exceptionally wet (1983). In 1983, soil moisture explained 98% of the variation in the survival of A. hallii seedlings and 82% in B. gracilis seedlings. Competition from existing vegetation severely limited the probability of seedling establishment. The distribution pattern of ridge species likely results from differential survival of juveniles and adults along the gradient, rather than the ability of seedlings to have higher establishment success on ridge sites. Significant establishment of the valley species (Bouteloua gracilis) occurred only during an exceptionally wet year when the pattern of survival of seedlings reflected the distribution pattern of adult plants. Establishment of prairie grass seedlings appears to depend on the availability of soil moisture, which may only be adequate in relatively large disturbance areas (> 1 m2), or in years of higher than normal precipitation.

Plant Growth and Survival under Strict Anaerobiosis

Anaerobic incubation of seedlings and rhizomes reveals interspecific differences in the ability of seedlings and rhizomes of higher plants to survive under prolonged and strict anaerobiosis. Rhizomes of several species were killed by an anaerobic incubation at 22 °C for 7 d while others survived and showed normal shoot extension on return to aerobic conditions. A third group of species showed healthy and geotropically normal bud and shoot extension while their rhizomes were in the oxygen free environment. A detailed comparison of bud and shoot growth rates was made with Scirpus maritimus under aerobic and anaerobic conditions over a 14 d period. Under similar conditions four species of grass seedlings were subjected to anaerobic conditions for 2-8 d at 5 °C, 15 °C and 25 °C. Seedling mortality was highest at 25 °C in all four grasses. Interspecific differences were evident. The wetland species were more tolerant of anoxia than the

Chilling Resistance in Lycopersicon hirsutum Humb. & Bonpl., A Wild Tomato With a Wild Altitudinal Distribution

Chilling resistance and other adaptations to low temperature were investigated in the wild tomato, Lycopersicon hirsutum, and the domestic tomato L. esculentum. Chilling resistance was assessed by the ability of seedlings to survive and grow after being exposed to 0°C for several days. For geogra- phical populations of L. hirsutum, chilling resistance was greatest in those derived from the higher altitudes. Other characteristics that correlated with the altitude of origin of the different populations were the rate at which the seeds germinated at low temperatures and chlorophyll development at low temperatures. L. esculentum cv. Rutgers did not tolerate chilling well and, in this respect, resembled low-altitude populations of L. hirsutum. L. hirsutum is a suitable species for physiological studies of chilling resistance, and its altitudinal variants are potential sources of genes 'tailored' to different temperature environments. Methods based on the above-mentioned responses to chilling may enable selection of chilling-resistant seedlings from hybrids of L. esculentum and L. hirsutum.