Technique for evaluating the potential for growth of shoot and root buds of white clover (Trifolium repens)

Abstract

S U M M A R YAn assay was developed for assessing the potential for growth of shoot and root buds of white clover. This paper describes the technique and the experimental results on which it was based. The assay involved the incubation of nodes under standard conditions and the monitoring of bud activity at the nodes. Shoot buds were of primary interest but the assay was also used to investigate the activity of root primordia. Correlative influences were reduced by separating individual nodes and by removal of their subtending leaves and petioles. The optimal environmental conditions for incubation were: a constant temperature of 20 °C, a 24 h photoperiod of low irradiance (4 W/m 2 ) and a high relative humidity (^ 90%). The technique proved suitable for the monthly screening of 1000-2000 nodes sampled from field populations of white clover.

Growth of White Clover Ecotypes, Cultivars, and Germplasms in the Southeastern USA

“…Despite the predominance of small‐leaf white clover in perennial Southeastern pastures, breeding efforts have produced large‐leaf germplasm, such as Brown Loam Synthetic No. 2 (Knight et al, 1988) and Southern Regional Virus Resistant (Gibson et al, 1989), and cultivars, such as Tillman, Regal, and Osceola (Williams, 1987) selected primarily for superior yield and disease resistance, often in clipped plots. However, under continuous cattle stocking in a mixed grass species pasture typical of the southeast USA, Osceola, Louisiana S‐1, Brown Loam Synthetic No.…”

Tiller hierarchy and defoliation frequency determine bud viability in the grass Poa ligularis

“…At the beginning of the dry season during late spring, early summer (December-January: end of the growing season: Giorgetti et al 2000), there was an increase in the percentage of dead and dormant buds per stem base in all stem base hierarchies; this has been shown in other grass and legume species (Newton and Hay 1992;Painter et al 1993). This reduction in bud metabolic activity towards a dormant stage might have been associated with (1) defoliation treatment effects (Busso et al 1989), (2) differences in light quality and quantity that reach the stem bases (Deregibus and Trlica 1990), (3) air temperature (Newton and Hay 1992) and water stress (Busso et al 1989) increases, (4) tissue senescence or necrosis (Davies and Evans 1990) and/or (5) deterioration of the bud vascular bundles (Gifford and Evans 1981). Growth arrest and entrance to a dormant stage may secure survival in perennial grass species in semiarid environments, where summers present scarce or no precipitation, by protecting and maintaining meristem viability (Koller 1969).…”

Viability of axillary buds of white clover (Trifolium repens) in grazed pasture

“…Dekker & Chandler 1985;Busso et al 1989) reveals respiring tissue and so distinguishes living from dead buds. The incubation technique used here has been shown to give a reliable determination of bud viability (Newton & Hay 1992). A refinement of the technique of Newton & Hay (1992) was the addition of a fungicide (Benlate) to the water used to soak the substrate.…”

“…In addition to a visual inspection, each node was excised by cutting through the middle of the adjacent internodes with a scalpel; any roots or subtending leaves were cut off. The nodes were then incubated al 20 °C in a 24 h photoperiod of low irradiance (4W/m 2 ) and a high relative humidity (^9 0 % ) , conditions which are optimal for bud activity (Newton & Hay 1992). Bud activity was visually assessed at intervals over the following 27 days and the emergence of flowers or branches was recorded; any buds which grew under these conditions were considered viable.…”

“…A combination of observation and assay techniques (Newton & Hay 1992) can be used to classify axillary buds into bud viability categories (Table 1) corresponding with the bud states shown in the developmental flow diagram (Fig. 1).…”