Plant Propogation and Nursery Management

Sexual Propagation

• Sexual reproduction refers to multiplication of plants by seeds. Seeds are formed after successful pollination and fertilization (Fig.1.1) by the union of male and female gametes.
• Meiosis division takes place in the course of fusion and the chromosome numbers are reduced to half, which after fertilization becomes normal.
• The plants raised through seed are called seedling plants.
• Propagation of plants by seeds offers many advantages however several have disadvantages too.
• Sexual propagation involves careful management of germination conditions and facilities and knowledge of the requirements of individual kind of seeds.

Fig.1.1: Stages of sexual reproduction

Success of seed propagation depends upon fulfilling the following conditions:

• Using seed of proper genetic characteristics to produce the cultivar or species, of provenance desired. This can be accomplished by obtaining seed from a reliable source or dealer.
• Using good quality seeds which germinate rapidly and vigorously to withstand possible adverse environmental conditions in the seed bed and provide a high percentage of usable seedlings.
• Manipulating the seed dormancy by applying pre-germination treatments or proper timing of planting.
• Providing proper environment for seed germination i.e., supplying sufficient water, proper temperature, adequate oxygen and either light or darkness (depending upon kind of seed) to the seeds and resulting seedlings until they are well established.

Advantages: Sexual method of propagation has several advantages, like

• Propagation by seeds is simple and easy.
• Seed propagation is only mean of diversity particularly in the selection of chance seedlings.
• Seedling plants are long lived, productive and have greater tolerance to adverse soil and climatic conditions and diseases.
• Seed propagation makes feasible to propagate plants like papaya and coconut in which asexual means of propagation is not common.
• Hybrids can only be developed by sexual means.
• Sexual propagation offers opportunities of polyembryony (citrus, mango or jamun) and apomixis (Malus sikkimensis, Malus hupehensis, Malus sargentii), which produces true- to - type plants.
• Seed is the source for production of rootstocks for asexual propagation.
• Seeds, if stored properly can be kept for longer duration /period for future use.

Disadvantages: Sexual method of propagation has some disadvantages, like

• Seedling plants are not true to type to the mother plants due to heterozygous nature of fruit plants.
• Seedling plants have long juvenile phase (6-10 years) and hence flowering and fruiting commences very late.
• Sexually raised plants are generally tall and spreading type and thus are cumbersome for carrying out various management practices like pruning, spraying, harvesting etc.
• Seeds of many fruits are to be sown immediately after extraction from the fruits as they lose their viability very soon e.g. cashew nut, jamun, jackfruit, citrus, mango and papaya.
• The beneficial influences of rootstocks on scion variety cannot be exploited in sexual propagation.
• Seedling plants usually produce fruits of inferior quality.