Abstract• We studied the effects of acorn cotyledon loss by insect damage and artificial excision on germination and seedling survival of Quercus variabilis, to determine whether insect infestation decreases acorn germination and seedling establishment; and to what extent cotyledon damage can affect acorn germination and seedling establishment.• Artificial excision partially imitated the effect of insect damage on acorn germination and seedling survival, and indicated that insect damage did not significantly decrease germination rate and seedling survival of Q. variabilis acorns. The viability of infested but still viable acorns strongly depends on which sector weevil larvae feed on.• The cotyledon reserves at the apex of acorns were more important than those at the base in supporting acorn viability and seedling establishment. The excision of apical cotyledon has the most detrimental effects on acorn germination activity. The relatively low effect of larval infestation on acorn viability was likely related to the high frequency of feeding and escaping at the base, which was closely correlated with differentiation in pericarp thickness in Q. variabilis acorns. These could explain the low decrease in acorn germination and seedling survival experienced by infested acorns.

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Tree peony is a famous ornamental plant in the world. However, little is known about the leaf color mutants in tree peony. The present study monitored the physiological and photosynthetic properties of a yellow leaf mutant (yl1) in tree peony. The results showed that the yl1 mutant had lower pigment contents, but increased chlorophyll (Chl) a/b and carotenoids to Chl ratio. Microstructure and ultrastructure analysis showed that the yl1 mutant had smaller chloroplasts, few thylakoid stacks, and a few stroma thylakoid membranes remained along with clusters of osmiophilic granules, which might result from inhibition at the reactions from coproporphyrinogen III to protoporphyrin IX. The yl1 mutant had lower leaf net photosynthetic rate, stomatal conductance, transpiration rate, and stomata limitation value, but higher intercellular CO2 concentration. Analysis of simple sequence repeat markers indicated that four pairs of primers could obtain different bands in the genome of the yl1 mutant compared to the wild type.

The effect of clipping height on ryegrass regrowth was investigated by examining the roles of several plant hormones. Our study consisted of three treatment conditions: (1) darkness over whole plants, (2) darkness only over stubble leaf sheaths, and (3) light over whole plants. Results showed that under darkness over whole plant, low stubble height resulted in low leaf regrowth biomass. Similar leaf regrowth biomass was observed under conditions of darkness only over stubble leaf sheaths as well as light over whole plants. Each unit weight of stubble at different clipping heights has relatively similar potential of providing stored organic substance for leaf regrowth. Therefore, regrowth index, calculated as newly grown leaf biomass divided by unit stubble weight, was used to evaluate regrowth capacity at different clipping heights under minimal influence of organic substances stored in stubbles. Under light over whole plants and single clipping, low stubble height and high stubble height with root thinning resulted in low leaf biomass and high regrowth index. On the other hand, under light over whole plants and frequent clipping high leaf biomass and regrowth index were observed in high stubble height. In addition, we found that leaf zeatin and zeatin riboside (Z + ZR) affected ryegrass regrowth and that roots regulated leaf Z + ZR concentration. Thus, our results indicate that root-derived cytokinin concentration in leaves influences ryegrass regrowth at different clipping heights.