Impacts of Salinity on Germination, Growth, Oxalate and Inorganic Ion Relations

Kochia (Kochia scoparia (L. ) Schrad.), an introduced annual herb with a wide geographical distribution, has a potential as a high yielding forage plant for saline soils. However, the autecology of kochia in general, and the Saskatchewan populations in particular, is virtually unexplored. Germination and early seedling growth responses of different populations of kochia to salinity and water stress were studied under controlled conditions. Populations from saline habitats exhibited greater reduction in germination with increased salinity than those from nonsaline habitats. Kochia from Texas was more tolerant of water stress at the germination stage than Saskatchewan populations. Both Saskatchewan and Texas populations were tolerant of low temperature at the germination stage, but the northern population maintained greater seedling growth under low temperature, particularly at high salinity. Kochia responded to salinity by reduced plant water and osmotic potentials, increased stomatal resistance, and maintained turgor pressure. It also responded to soil-induced water stress by decreased plant water potential and increased stomatal resistance. The Saskatchewan populations had similar water relations in response to soil-induced or atmosphere-induced water stress. Kochia from a Saskatchewan saline habitat was more resistant to water loss from its leaf tissues in response atmosphere-induced water stress than that from Texas. Growth room and field investigations were conducted to determine the ionic relations and growth response to salinity of a number of kochia populations. Kochia accumulated oxalate in all plant parts, with highest levels in mature leaves and lowest in roots, and intermediate levels in young leaves and stems. Water-soluble oxalate levels exceeding the safe limits for ruminants were found in mature leaves. Leaf oxalate correlated positively with soil osmotic potential but negatively with soil sulphate, chloride, total cations, and matric potential. Oxalate levels were also significantly correlated with plant ion concentrations. The growth room experiments showed generally similar relations but also indicated interpopulation variations in the capacity to accumulate oxalate. Kochia responded salinity by increased internal inorganic ion concentration, with highest accumulation in mature leaves. Ion levels in kochia varied with the concentration and composition of ions in the external medium. In contrast to most halophytes which accumulate sodium even under low salinity, K+ was the principal cation in kochia plants under nonsaline or low salinity conditions. High Mg and Na depressed K+ and total Ca++, but increased soluble Ca++ levels in the plant. Sulphate and Mg++ levels in shoots exceeded their safe limits for livestock. Total Cats concentrations were high in kochia, but the soluble Catt levels were below the animal nutritional requirements. Early growth response to salinity of a lowland and an upland populations was comparable, but the latter was more tolerant to salinity than the former during a more advanced growth stage. Kochia from a saline habitat in Saskatchewan was more salt tolerant than kochia from Texas. Yield reduction was related to external salinity and to mature leaf succulence. The two populations showed also some differences in ionic relations.

Name thesis:degree_name

Doctor of Philosophy (Ph.D.)

Level thesis:degree_level

Doctoral

Discipline thesis:degree_discipline

Crop Science and Plant Ecology

Grantor

University of Saskatchewan

Year dc:date.issued

1992

Author dc:creator

• Abouguendia, Zoheir Mohammed

Handle dc:identifier.uri

https://hdl.handle.net/10388/17018

OAI identifier oai:identifier

oai:harvest.usask.ca:10388/17018