Abstract: Methods for reducing nitrate nitrogen and oxalic acid contents in plants, each of which comprises applying 5-aminolevulinic acid, a salt thereof or a mixture thereof. Nitrate nitrogen and oxalic acid contents in plants having high nitrate nitrogen and oxalic acid contents can be reduced effectively and easily.

Abstract: A method for improving pigmentation of the rind of anthocyanin-containing apples comprising treating fruit-bearing apple trees or apples before or after harvesting with an effective amount of an agent which comprises 5-aminolevulinic acid, a salt thereof or a mixture thereof as an active component.

Abstract: A method for treating plants with a plant growth promoter comprising 5-aminolevulinic acid or a salt thereof as an active ingredient. This treatment method is effective in enhancing the photosynthetic activity of a plant, enhancing its ability to absorb CO.sub.2, suppressing its respiration, increasing its chlorophyll content and promoting its growth. As a result, the treatment greatly contributes to the promotion of rooting, the reduction of lodging, an increase in yield, an improvement in cold resistance, maintenance of freshness, an improvement and maintenance of green color, the growth of good seedlings, the promotion of organs, an increase in tillers, a shortening of the time required for growth, a relief of chemical damage and an increase in the rooting ratio in, for example, cutting.

Abstract: Multi-layered crosslinked ethylenic resin films comprising a laminate of at least two ethylene resin layers crosslinked by irradiation with ionizing radiation are constructed in that an outer layer contains at least one specific crosslinking controlling agent such as hydrogenated terpene resin in a higher concentration than in an inner layer. The films are advantageously applicable to shrink packaging for foodstuffs.