Incandescent lamps

Seeds of Norway spruce [Picea abies L. (Karst)] (59°N, provenance CØ1 from Halden, Norway, seed lot 98063, Skogfrøverket¹) were sown and seedlings grown at 18°C in a 3:1 mixture of fertilized peat:perlite as previously described (Holefors et al., 2009 (link)). The relative air humidity was adjusted to 0.5 kPa water vapor pressure deficit. The photon flux density of the main light period of 12 h was 180 μmol m^-2 s^-1 at 400–750 nm from high-pressure sodium lamps (General Electric, United States) supplemented with 8 μmol m^-2 s^-1 from incandescent lamps (Osram, Germany). To obtain LD conditions, the light period was extended to 24 h with low-intensity light from incandescent lamps (8 μmol m^-2 s^-1, Osram). After 8 weeks, a subset of plants was transferred to SDs with a 12 h photoperiod with light conditions as in the main light period of LD and 12 h darkness. All other conditions were the same as for LD. After 8 weeks of SD, the plants were again placed under the LD conditions. In 30 plants per treatment, the plant length was measured from the soil base in the pot to the shoot tip/apical bud or to the tip of the longest needle, and elongation growth was calculated. To determine which of the apical needles were the longest, these needles were carefully bent upward.

The four lines of pea (P. sativum L.) seeds (JI 116, JI 2822, JI 1184, and JI 3020) in this study were selected based on the presence of specific alleles at the Def locus, which control the detachment of the seed from the funiculus (Ayeh et al., 2009 (link), 2011 (link)). Two wild types (WT) with the Def locus and two def mutant pea seeds were kindly supplied from the John Innes Pisum Collection Ayeh et al. (2009 (link)). Tall wild type (JI 116) and dwarf wild type (JI 2822) develop normal abscission events and therefore abscise the seed from the funiculus through the intervening hilum region. The tall def mutant (JI 1184) and the dwarf def mutant (JI 3020) both lack the abscission event and therefore fail to abscise the seed from the funiculus. These lines have a deficient abscission zone, which we have given the name abscission-zone-less (AZL; Ayeh, 2008 ). Seeds of each line were sown in pots with fertilized peat and grown under greenhouse conditions at 22°C and 16/8 h photoperiod with a photon flux of 110 μmol m⁻² s⁻¹ [400–700 nm Photosynthetic Active Radiation (PAR)] and a daylength extending light provided from incandescent lamps (OSRAM, Germany).

The four lines of pea (Pisum sativum L.) seeds (JI 116, JI 2822, JI 1184 and JI 3020) in this study were selected based on the presence of specific alleles at the Def locus, which control the detachment of the seed from the funicle [4 (link)]. Two WTs and two def mutant pea seeds were kindly supplied from the John Innes Pisum Collection (Table 1). Tall WT (JI 116) and dwarf WT (JI 2822) have a normal abscission of seeds. Tall def mutant (JI 1184) and dwarf def mutant (JI 3020) both lack the seed abscission. The seeds of each line were sown in pots with fertilised peat and grown under greenhouse conditions at 22 °C and 16/8 h photoperiod with a photon flux of 110 μmol m⁻² s⁻¹ (400–700 nm photosynthetic active radiation) and a day length extending light provided from incandescent lamps (OSRAM, Germany).Table 1

Details of Pisum sativum L. accessions and their allelic status with respect to the Def locus

Accession	Name	Def allele	Phenotype
JI 116	cv. Parvus	Def (wild type)	Tall
JI 2822	RIL, research line	Def (wild type)	Dwarf
JI 1184	Priekuskij-341-def	def (mutant)	Tall
JI 3020	cv. Nord	def (mutant)	Dwarf