Physiological responses of rice (Oryza sativa L.) to seed and seedbed management and silica application under flooded conditions / Evangeline F. Salcedo-Ella ; Maribel L. Dionisio-Sese, chair, advisory committee.

Date

6-2011

Abstract

Waterlogged and flooded fields reduce seedling survival and hinder early growth and crop establishment in rice (Oryza sativa L.). Flood-prone rainfed areas are highly populated, where annual yield loss was estimated at about 3.2 million tons valued at US dollar 400 million. This study assessed the physiological responses of two sets of rice genotypes, one set contrasting in flooding tolerance at germination and early seedling stages and other set at vegetative stage. Effects of seed age, seed storage temperature, seed pre-treatments (priming and soaking before sowing), and floodwater conditions (temperature, depth, algal growth) on seedling growth and survival in flooded soil at germination and early seedling stages revealed the following results. Seedling survival decreased in 1- to 2-yr old seeds than in newly-harvested seeds, and in seeds stored at higher temperatures of 25-27oC than in cold storage of 5-8oC. This reduction in survival was associated with lower superoxide dismutase (SOD) and catalase (CAT) activities and greater lipid peroxidation. Survival, shoot and root growth, and amylase activities measured three days after sowing were highest when floodwater temperature was 24-26oC. Survival decreased with algal growth in floodwater and with increasing flooding depth. It was observed that soaking or priming seeds with tap water for 24 h or salt solutions with water potential of -1.50 and -2.25 MPa for up to 48 h increased survival and improved seedling establishment, especially in the tolerant genotypes. Prolonged priming with water for 48 h, however, had negative effect on embryo viability. It was noted that priming with KCI had higher survival than CaCl2 solution. These seed pre-treatments lowered lipid peroxidation due to higher SOD and CAT activities whereas carbohydrate mobilization and starch breakdown were hastened due to higher amylase activities. On the other hand, effect of soil amelioration with silica 1 day before sowing on seedling growth and survival after flooding at the vegetative stage resulted in increased shoot growth and chlorophyllase activity, reduced stem starch concentrations during flooding, and decreased seedling survival. Survival correlated positively with amylase activity and negatively with lipid peroxidation and chlorophyllase activity. Results from this study showed that tolerant genotypes were more responsive to various management practices, emphasizing the effectiveness of adopting the appropriate management practices to improve seedling establishment of tolerant rice genotypes under flooded conditions.

Document Type

Dissertation

Degree

Doctor of Philosophy in Botany

College

Graduate School (GS)

Adviser/Committee Chair

Maribel L. Dionisio-Sese

Co-adviser

Abdelbagi M. Ismail

Committee Member

Maribel L. Dionisio-Sese, Abdelbagi M. Ismail, Teresita H. Borromeo, Lourdes B. Cardenas, Azucena L. Carpena

Language

English

LC Subject

Seeds, Rice, Waterlogging (Soils), Rice, Germination, Botany Institute of Biologial Sciences

Location

UPLB Main Library Special Collections Section (USCS)

Call Number

LG 996 2011 B62 S25

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