Salt avoidance and tolerance in beach pea (Lathyrus maritimus (L.) Bigelow) : a study of the effects of salinity on germination, growth, photosynthesis, and respiration in comparison to common forage legumes

Reid, Todd A. (2001) Salt avoidance and tolerance in beach pea (Lathyrus maritimus (L.) Bigelow) : a study of the effects of salinity on germination, growth, photosynthesis, and respiration in comparison to common forage legumes. Masters thesis, Memorial University of Newfoundland.

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Abstract

Beach pea (Lathyrus maritimus (L.) Bigelow) is a lush green legume which grows along the shores of the island of Newfoundland. It is a circumpolar plant found on both sea shores and the shores of freshwater lakes. Beach pea is a fleshy perennial with an extensive rhizome system. The roots form nodules that contain bacteria (Rhizobium sp.) which provide fixed nitrogen to the legume for incorporation into proteins of the host plant. Beach pea form large persistent stands on beaches and has been studied for its potential as an alternate forage crop. The plants that grow on salt water beaches are exposed to salt water spray inferring some level of salt tolerance in the plant. The objectives of the thesis were to compare salinity effects on beach pea germination relative to other forage crops and to study salinity effects on growth. -- Slightly increased salt concentration delayed beach pea germination more so than that of alfalfa and red clover, contrary to the initial hypothesis that beach pea germination would show higher tolerance for saline environments. Red clover and alfalfa were affected only at salt concentrations of 1.75 and 2.0 percent whereas beach pea germination was affected at 0.50 percent salinity. Final germination percentage relative to germinating salinity followed a sigmoidal pattern in all crops, dropping rapidly around 1.0 percent NaCI. Growth in saline environment effectively stopped the growth of beach pea by limiting stem elongation, new stem initiation, and new leaf initiation. Alfalfa mortality was observed as a result of the saline environment with a 50 percent mortality in the 2 percent saline environment 10 weeks after planting and 100 percent at 15 weeks. The 1 percent saline environment also increased mortality in the alfalfa to 60 percent by week 16. Control plants showed no mortality over the 16 week experiment. -- The delay of germination and inhibition of new growth seen in the beach pea did not support the hypothesis of the experiment. Salinity measurements of the natural beach environment showed low soil salinity level relative to salinity in the tide line. At the high tide line salinity was 20 times higher than the salinity in the beach pea stands. The experiments show that the environment in which beach pea grows is not saline. Salinity delays germination but the plants, once established, are salt tolerant. In a natural stand of beach pea exposure to a saline environment would be temporary as fresh water from rain or seeps would remove the salt before any accumulation and thus plant damage could occur.

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