Influence of elevated CO2
The increase in atmospheric CO2 is reported not only to improve the yield but also to alter the quality of the produce. The quality (carotene, starch, and glucose content) starchy fruits increased in elevated CO2 conditions. Under high CO2 level, the water use efficiency of crops is reported to increase.
What are the damages caused by high temperature?
- In summer the leaves, new shoots, branches, flowers, and fruits are exposed to sun and high temperature. The high temperature is generally more harmful when accompanied by low humidity. This causes excessive transpiration and wilting of leaves and twigs.
- The ability of plants to withstand such condition varies greatly with species; e.g. banana is more sensitive than guava plants.
- Young trees are affected more than old plants.
- High temperature and low humidity is a limiting factor in a case of certain fruits like banana.
- Sunburn of leaves, fruits (pineapple) and bark is sometimes a serious factor. Plants planted in an east and south aspect are more affected than in other directions as they are exposed to sunlight for the longer time.
- Flowering and fruit set are adversely affected by high temperature as in mango and mandarin. Citrus fruits suffer a production loss when temperatures over 37oC are experienced
- Planting of thick and tall growing windbreaks are required to be planted at the time of orchard establishment.
- Severe pruning of trees is avoided during the summer season.
- Adopt protection measure before the commencement of high temperature. Whitewashes the main stem and also small branches and young plant shoots at the beginning of summer season.
- Irrigate properly to have more humidity in the orchard.
- Spread the mulch in the basins of young and old trees. Provide grass cover to fruits as in pineapple.
Effects of low temperature on plants
- Low temperatures (Freezing) occurring either during the rest period of fruit plants or afterward, cause damage to roots, stems, and buds. At lower temperatures, water is withdrawn from protoplasm and ice is formed in the intercellular spaces. If this process proceeds beyond critical limits the protoplasm of the cells disintegrates and dies from loss of water.
- Frost causes damage to the newly opened blossoms of fruit trees, to young growth and newly set plants. Frost occurs when there is sufficient moisture in the air and the temperature of the exposed surfaces fall below 32oF.
- Important types of injuries due to occurrence of frost observed in fruit plants are (1) Blackheart—Inner wood of nursery fruit plants becomes dark; (2) Splitting of bark—this may be extended to trunk and branches; (3) Killing of shoots and young branches— if there is early growth in spring and flowering in fruits like mango, flowers may be killed while in others like citrus and papaya even fruits are injured; (4) Frost damage—evergreen tree are damaged heavily but deciduous fruit trees shed their leaves and not normally damaged. In young fruit plants, the damage is very severe.
- Delicate young fruit plants are planted on the inner side of the orchard.
- Windbreaks should be planted in time on west and north side of the orchard.
- Apply adequate manures and fertilizers to make the plants stronger and more tolerant.
- Plants of frost tolerant varieties are given preference for planting in the new orchard.
- Irrigated orchards regularly during the frost periods.
- Burn dry leaves and twigs in orchards (10 – 12 places in one hectare).
- Cover the trunk with grass. The young plant may be covered on three sides leaving southeast side exposed for light and the sun.
- Plants quick growing green manuring crop around a young plant to provide protection.
- Climate change has been a cause of serious concern if the fruit industry has to grow in the context of country’s overall economic growth, to respond to rural households’ livelihood, country’s nutritional security and poverty alleviation.
- It may take some years to fully experience the devastating effects of climate change on quality fruit production but the time is ripe for the Government, private sector and public to have the adequate concern, commitment and accountability to mitigate the effects of climate change.