Present address: Ministry of Jihad-e-Sazandagi, Tehran, Iran.Abstract The effects of row spacing (15, 30, 45, and 60 cm) and sowing rate (1, 3, 6, and 12 kg/ha) on lucerne seed yield and its components were investigated at Massey University, Palmerston North, New Zealand, over two seasons. In the first year, seed yield from the 15 cm row spacing was significantly lower than that from the 30, 45, and 60 cm row spacings, whereas sowing rate had no effect on seed yield. In the second year crop, row spacings did not significantly affect seed yield, but the seed yield from the 1 kg/ha sowing rate was significantly greater than that for other sowing rates because harvestable racemes/m 2 and thousand seed weight were significantly increased. Seed yield over 2 years of the experiment was highest at the 1 kg/ha sowing rate and for the 30 and 45 cm row spacings. However, there were no significant interactions between row spacing and sowing rate for seed yield. The average seed yield for all treatments was 127 and 187 kg/ha for the first and second year respectively. Neither row spacing nor sowing rate had any effect on the quality of harvested seed.

A study over two years involving tiller identification according to month of origin enabled the contribution of individual tillers of perennial ryegrass Grasslands Ruanui, timotby Grasslands Katbu and a local New Zealand strain of prairie grass (Bromus unioloides) to be deternnined at seed barvest. In addition, tbe distribution of seedbeads in different arbitrary emergence groups was detennined so as to allow analysis of individual seedhead components witbin each group.In all species, tillers formed during tbe first 4 months following an autumn sowing in tbe first year, and also in tbe immediate post-barvest period and tbrougb tbe autumn in tbe second year, made a major contribution to seedhead numbers and seed yield at harvest. These tillers bad a lower vegetative mortality rate than those formed in the spring.Primary tillers formed after sowing were highly persistent and became almost exclusively reproductive. Many vegetative tillers died before barvest, bebaving as annual tillers.Spring-formed tillers made a major contribution to tbe vegetative growtb of tbe plant over the summer and early autumn. These tillers generally died before the following winter. Tillers formed in winter and early spring by ryegrass and prairie grass sbowed a bigb mortality, particularly in tbe second year. In timotby, mortality was bighest amongst tillers formed in late spring. Tbe reduced contribution of spring-formed tillers to tbe seedbead population occurred as a result of fewer beads numerically compared with older tillers.In all species, most seedhead components varied according to time of ear emergence. Earlyemerged heads were generally longer, bore more spikelets and more florets per bead and bad a greater culm lengtb tban late-emerged beads.Tbe major trend in all species was a general depression in bead lengtb, spikelet and floret number and culm lengtb witb grazing. Tbese effects were in most cases partly or completely overcome by N application. Tbe major effect of applied N was to increase floret number per bead.

Hollow heart, a pea seed disorder, reduces pea seed vigour. It is associated with high temperature after seed set, but the susceptible seed development stage is not entirely clear. A field trial in New Zealand involving three sowing times (September, October, and November 2003) and three garden pea (Pisum sativum) cultivars ('Rainier', 'Early Onward', and 'Alderman') was conducted to determine if the predisposing stage to the disorder couldbe identified. Hourly thermal time (HTT) at a base temperature (T b ) of 25°C when seed moisture content (SMC) was 70-80% was correlated positively with hollow heart incidence at harvest maturity (HM), but this response differed among cultivars. HTT (T b = 25°C) when SMC was 15-25% was not correlated with hollow heart incidence at HM, if data for all cultivars were included in the correlation analysis. However, an increase in hollow heart incidence after seed had dried to between 15% and 25% SMC occurred with increasing HTT (T b = 25°C) in 'Alderman'. These results demonstrate that there are genetic differences in susceptibility to hollow heart. The hypothesis that hollow heart is associated with a starch deficiency in the adaxial region of the cotyledons, and that cultivar differences are related to differing efficiencies of assimilate transport into seeds at high temperatures is discussed.

This paper considers the sequence of seed development by measurement and observation of ehanges in seed moisture content, weight, colour, endosperm consistency, germination capacity and yield tn perennial ryegrass Grasslands Ruanui, timothy Grasslands Kahu and a New Zealand strain of prairie grass (Bromus unioloides).

Plants of two garden pea (Pisum sativum) cultivars ('Alderman' and 'Early Onward') were exposed to high temperature (30/25°C; day/ night, 12h each) at five different stages (during seed development, S1-S2; at physiological maturity (PM), S3; and during seed maturation, S4-S5) to determine the effect of high temperature on seed quality parameters and the location of deteriorated tissues within the cotyledons at each stage. High temperature applied at the beginning of seed filling (S1) significantly decreased thousand seed weight in both cultivars, and germination in 'Alderman'. Hollow heart was significantly increased in both cultivars when high temperature was applied at the rapid seed fill stage (S2), but not when applied at other stages. There was a significant cultivar by treatment duration interaction at S2 for hollow heart incidence-'Alderman' was more susceptible to hollow heart than 'Early Onward'. Single seed conductivity was significantly increased by high temperature at S4 and S5 in both cultivars, and in 'Alderman' high temperature at S1-S3 also increased leachate from the seeds. cells within the cotyledons differed depending on the timing of the high temperature treatment. Treatment at S2 resulted in deterioration at the adaxial surface of the cotyledons; with treatments at S4-S5, deterioration occurred at the abaxial cotyledonary surface. The results suggest that the susceptible portion of pea cotyledons to high temperature during pre-PM stages is different from that during post-PM stages, and that the hollow heart test and the conductivity test detect deterioration located at different positions within the cotyledons. This may lead to the occasional inconsistency between the two tests.