Sugarbeet Fruit Germination and Emergence under Moisture and Temperature Stress1

Abstract

Poor fruit germination and emergence of sugarbeet (Beta vulgaris L.) due to moisture and temperature stress can limit satisfactory stand establishment. Our objective was to evaluate laboratory procedures which measure germination and emergence potential under moisture and temperature stress and to use these tests for development of fruit treatments for improving field emergence under stress conditions.Germination tests were conducted on blotter paper using polyethylene glycol 600 osmotic solutions to induce moisture stress. Emergence through a 2.5 cm layer of greenhouse soil mix (Ascalon sandy loam and peat, 1:1 V/V) was used to evaluate the effect of fruit treatments on emergence under moisture and temperature stress. The soil mix, initially at —1/3 bar matric potential, dried to —10 to —5 bar matric potential during the course of the test. Emergence through a 3.3 can layer of packed silica sand (3.5% water — wt/wt) was used to evaluate treatments under temperature, moisture and impedance stress tests conducted at 9, 15, or 26 C. Field trials were used to confirm results of laboratory tests.Germination of sugarbeet fruit decreased with increas. ing osmotically simulated moisture stress from 0 to —7 bar water potential after which no germination occurred. Increasing the moisture stress from 0 to —4 bar potential decreased the rate of germination, but not the final germination percent, while both rate and final germination percent decreased sharply as moisture stress went from —4 to —8 bars. Removal of the pericarp decreased the water requirement for germination at a given rate by 2 bars, indicating that the pericarp is a major factor limiting germination and emergence under moisture and temperature stress.Treatment of the fruit with 1.0 N HCI for 2 hours significantly improved germination and emergence under moisture and temperature stress conditions in laboratory and field trials. Excessive acid treatment damaged the true seed. The acid treatment did not improve the emergence where impedance was the major stress or in the absence of moisture and temperature stress. Temperature affects not only the rate and extent of germination, but also the moisture requirement. The sugarbeet fruit germination at —5 bar matric potential and 26 C was equal to that at —1 bar and 9 C.The germination of untreated fruits of eight cultivars ranged from 26 to 72% at —1 bar matric potential and 9 C, and from 6 to 20% at —5 bar and 9 C. Acid treatment improved germination of all cultivars, but low germinating cultivars were improved the most.