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Variations in Soil Moisture and pH Tolerance of Narra (Ptetocarpus indicus Willd.) Seedlings
Dissertation Abstract:
The study was conducted to determine variations of narra (Ptecocarpus indicus Willd.) provenances tested in varying soil moisture content and soil pH and their interactions. The experiment portion used seeds collected from various provenances and bulked samples coming from 5 to 10 trees. The experimental design was a factorial experiment in randomized complete block design (RCBD). The seedlings were tended in the nursery for six months after which the different parameters were measured to assess the seedlings' response to the different treatments applied. Seedling height, root collar diameter (RCD), length of tap root, number of leaves, shoot biomass, root biomass, total biomass, root/shoot, leaf area, number of stomates, and relative water content were measured to evaluate the response of narra species to the different treatments.
Soil pH gave significant differences in various narra seedling morphological traits in he ight, root biomass, shoot biomass, total biomass, root/shoot ratio, length of tap root, and number of leaves. Overall assessment showed superior growth and vigor of narra seedlings at pH 5.8 and 6.4 than pH 7.8; suggesting that s lightly acidic soil (pH 5.8 and 6.4) enhanced good growth of seedlings.
Different provenances of narra gave varying phenotypic variations (morphological and physiological) as manifested by seedlings in RCD, shoot biomass, root/shoot ratio, length of tap root, number of leaves, and leaf area. PI (Tacloban City) provenance performed best among the provenances studied and should be the best choice as source of seeds for planting areas where soils were collected.
Moisture stress applied to the seedling at varying levels based on the field capacity gave significant results in RCD, root biomass, and total biomass. As expected, seedlings grown at 75 percent of the field capacity have superior growth compared to seedlings grown on soil with lower moisture. Since no seeding mortality was noted, narra seedlings can survive in soils with moisture content up to 35 percent of the field capacity given the same condition in the study.
The test for the genotype (G) and environment (E) interactions showed positive response in terms of seedl ing he ight, root/shoot ratio, number of leaves, and number of stomates. This resulted in a shift in provenance ranking at vary ing soil pH and moisture regimes.
Interaction of soil pH and moisture regimes showed significant differences on number of stomates. The highest number of stomates was greatest at pH 6.4 and mo isture regime M3 (65% of the field capacity).
Complex interaction of soiI pH provenance and moisture regimes gave significant diffe rences in he ight of the seedlings studied. The Tacloban City provenance showed the best seedling growth at pH 6.4 and 50 percent of the field capacity, while Baybay, Leyte; Bayombong, Nueva Yizcaya; Larena, Siquijor; and Mambusao, Capiz provenances performed better at soiI pH 5.8 and preferred 50-70 percent moisture based on the fi eld capacity.
Moreover, the results further showed that morphological traits of seedlings such as height, ROC, shoot, and total biomass can be used to determine variations exhibited by narra seedling response to varying soil moisture and soil pH. Assessment of seedling response to various treatments suggests that height should be used as a good indicator of seedling resistance to drought and pH for practical and economical reasons. Drought- and pH-tolerant seed lings have long shoots, bigger RDCs, heavier biomass, larger leaf areas, and balanced root and shoot in terms of weight.