Study On Reproductive Biology Of Kochiaprostrata

Kochia prostrata, a perennial subshrub belongs to Kochia Roth, which distributed in Mid-low Belt ofNorth slopes of Tianshan Mountains. In this paper, we observed the flowering phenology, characteristics ofbreeding system and seed germination of K. prostrata.The main rusults were as follows:1. The flowers of inflorescence of K. prostrata bloomed from up to down to top and middle floretsbloomed before outer florets. The flowers were aprotogyny and the flowering course of single flower ofthis species can be divided into female subage and male subage. The female subage can lasted for10to12days and the male subage was for1day. Protogyny is an effective way to avoid self-fertilize and promoteoutcrossing.2. K. prostrata produces two types of stigmas and anthers in colour (red and yellow). There are fourdiferernt combination types of stigma and anther in the K. prostrata population. The pollen viability of K.prostrata was highest at initial stage (＞80%), higher on the4to8hours after flowering, and then reducedevidently. The pollen viability of yellow-anthers was longer than the red-stigmas. The change tendency ofreceptivity of the two stigmas is similar. The stigma receptivity of K. prostrata appeared on the first day ofstigma break tepals, and then enhanced with the growth of stigma. The stigma receptivity were highest onthe8to12days after flowering. The period of stigma receptivity was about12days, account for92.3%ofsingle flower blooming.3. The variation of morphology of stigma and anther occurred commonly and the flowers wasaprotogyny. The outcrossing index and pollen-ovule ratio of K. prostrata were3and61900~64200,respectively. Seed setting rate was66.6±2.3%, and variability is small, which is a characteristics ofself-pollination.These indicated that outcrossing is the main form in breeding system of K. prostrata and itis also self-compatibility. Thus the K. prostrata appeared to have a mixed-mating system.4. The suitable thermoperiods for germination of K. prostrata seeds is30/15℃and25/15℃, and thegermination percentage＞85%. Low temperature significantly inhibited seed germination. Lowconcentrations of NaCl solution (≤0.1mol/L) stimulated germination, and have synergistic effect; The finalseed germination percentage of seeds under＜0.6mol/L NaCl concentrations was not significantlydifferent (＞80%). However, as the salt concentrations increased to1mol/L, germination percentagedecreased with increasing of salt concentration and there was a negative correlation between them. Afterallaying the salt stress, seeds have a partial germination recovery. The germination was decreased with theincreasing of salt concentration. The observed recovery germination under2mol/L and4mol/L saltconcentration was36%and39.6%, separately.In a word, Kochia prostrata has the special protogyny flowering characteristics, especially flowersyndrome, the facultative mixed breeding system, the wider thermoperiods for germination, the highergermination percentage and anti-salt germination percentage, those characteristics ensured variousreproduction process success of K. prostrata in the unpredictable desert environment.