Morphological characteristics of roots, stems, leaves, flowers and fruits of chrysanthemum.

Chrysanthemum seedlings have real main roots at seedling stage, and then many slender secondary roots grow from one node. Secondary roots also have ancestors, and lateral roots can occur many times to form a developed root system. After flowering, the stems wither and the roots die. In addition, from the foot buds at the base of plants, roots can be formed on underground stems buried in soil, which are called perennial roots. Roots can grow at the base of foot buds to form independent roots. When the foot buds are separated from underground stems and perennial roots, new plants can grow.

Step 2 stop

Stems erect, branched or unbranched, pilose. The stems of propagation seedlings are divided into two parts: aboveground stems and underground stems. The aboveground stems are 0.2-2 meters high and multi-branched. Young stems are light green or brownish in color, gray and fluffy. Most stems die after flowering. In the second spring, the underground stems grew evil buds.

Step 3 leave

Leaves alternate, short-stalked, ovate to lanceolate, 5- 15 cm long, pinnately lobed or cleft, cuneate at the base, white pubescent at the lower part, coarsely serrated or deeply lobed at the edge, and cuneate at the base and stalk. Chrysanthemum leaves are solitary and alternate, with petiole length of 1-2 cm, stipules or degeneration on both sides of the stalk, oval to oblong leaves, notched and serrated edges.

4. flowers

The flower heads are solitary or clustered at the top of stems and branches, with a diameter of 2.5-20 cm and different sizes, and one or several are clustered at the top of stems and branches; Because of different varieties, there are great differences. The involucral bracts are multi-layered, the outer layer is green, strip-shaped, the edge is membranous, and the outer side is pilose; Tongue flowers are white, red, purple or yellow.

Colors are red, yellow, white, orange, purple, pink, crimson and so on. There are many varieties cultivated, which are varied in size and variety. Shapes range from single petals to flat petals and spoon petals, among which tubular flowers are often specialized into various tongue-shaped flowers. Flowering: September-165438+1October. Stamens, pistils and fruits are mostly underdeveloped.

5. Fruit

Achene (commonly known as "seed") is1-3mm long and 0.9-1.2mm wide. Its upper end is slightly pointed, flat, wedge-shaped, with longitudinal ridges and brown surface. An endosperm-free seed is produced in the fruit, which matures in the following year 1-2, and the 1000-grain weight is about 1.

Extended data:

Chrysanthemum is a perennial herb with a height of 60- 150 cm. Stems erect, branched or unbranched, pilose. Leaves alternate, short-stalked, ovate to lanceolate, 5- 15 cm long, pinnately lobed or cleft, cuneate at the base, white pubescent at the lower part, coarsely serrated or deeply lobed at the edge, and cuneate at the base and stalk.

Chrysanthemum is a perennial semi-shrub. The stems of propagation seedlings are divided into two parts: aboveground stems and underground stems. The aboveground stems are 0.2-2 meters high and multi-branched. Young stems are light green or brownish in color, gray and fluffy. Most stems die after flowering. In the second spring, the underground stems grew evil buds. Chrysanthemum leaves are solitary and alternate, with petiole length of 1-2 cm, stipules or degeneration on both sides of the stalk, oval to oblong leaves, notched and serrated edges.

The shape of leaves varies with varieties and can be divided into eight categories: positive leaves, deep positive leaves, long leaves, deep long leaves, round leaves, sunflower leaves, awn leaves and boat leaves. Chrysanthemum (flower head), born at the top of the branch, is about 2-30 cm in diameter, and the flower bud is composed of green flowers outside the inflorescence.

There are two kinds of flowers on the inflorescence: one is a single flower, commonly known as "flower heart", the corolla is connected into a single shape, which is bisexual, with a pistil in the center, a 2-split stigma, and an ovary at the lower position of 1, which surrounds the five main medicinal stamens; The other is tongue-shaped flower, which is born on the edge of inflorescence and commonly known as "petal". The stamens in the flower degenerate, with 1 pistil.

Tongue-shaped flowers are colorful, and their shapes can be divided into five categories: flat, spoon-shaped, tubular, laurel-shaped and irregular. Achene (commonly known as "seed") is1-3mm long and 0.9-1.2mm wide. Its upper end is slightly pointed, flat, wedge-shaped, with longitudinal ridges and brown surface. An endosperm-free seed is produced in the fruit, which matures in the following year 1-2, and the 1000-grain weight is about 1.

Chrysanthemum varieties have great diversity, so taxonomists discuss the primitive ancestors of chrysanthemum. Or think that wild chrysanthemum is the original ancestor of chrysanthemum, or think that chamomile is the original ancestor, or think that its original ancestor is small red chrysanthemum, or list a series of possible original ancestors. Some scientists in China have also carried out interspecific hybridization experiments, and made some speculations and experiments in exploring the real source of chrysanthemum.

No matter speculation or experiment, we try to put the origin of chrysanthemum on one or two species of this genus, and try to point out which of these vast varieties is the most primitive, that is, to find out the most primitive chrysanthemum variety.

To be sure, the origin of chrysanthemum is varied, which is pluralistic rather than unit origin. Chrysanthemum is a cross-pollinated plant. In the long-term practice, people use interspecific hybridization or even interspecific hybridization to obtain new characters of chrysanthemum, and obtain the separation of new characters through sexual processes such as backcross and hybridization.

In this way, after gene recombination and character separation, there are more and more new characters. In this process, conscious artificial hybridization and random natural selection can occur simultaneously or alternately.

However, the manual selection process of eliminating the inferior and selecting the superior will always play a leading role. Chrysanthemum chromosomes are extremely limited. Only recorded chrysanthemum is hexaploid, 2n=54. Another possible way to produce new varieties of chrysanthemum is somatic mutation (bud mutation), and new varieties can be obtained by fixed bud mutation.

References:

Baidu encyclopedia-chrysanthemum