The food-conducting tissues of a plant, as opposed to the xylem, which conducts water. In general, the phloem carries carbohydrates downwards from the leaves, while the xylem carries water and minerals upwards from the roots. Phoenix dactylifera
The date palm, which has a sub-tropical, semi-arid origin in the Middle East. This is possibly the oldest plant domestication in the world. The plant is dioecious and breeding is exceptionally difficult. Propagation by seeds is a waste of time, because of the loss of fruit quality, and vegetative propagation with basal suckers is essential. The quality of the date fruit is affected by metaxenia. A new-encounter killer-disease, 'Bayoud disease' (Fusarium oxysporum f.sp. albidinis) is spreading inexorably from Morocco eastwards. Breeding is exceptionally difficult, but local people should be on the lookout for the rare, high quality, seedling palm that is also resistant to Bayoud disease. Phosphate
Compounds of phosphorus, phosphates are an essential plant nutrient. Organic phosphate fertilisers are usually rock phosphate or bone meal. The artificial phosphate fertilisers have had their soluble phosphate content increased by industrial means. Phosphate deficiency symptoms include poor growth, and leaves with a bluish-green to purple coloration. Photoperiod-sensitive
Photoperiod-sensitive plants depend on a particular day-length to initiate flowering or some other stage of development. For example, short-day potatoes will initiate tuber-production at any time of year in the tropics, where there is an approximately twelve-hour day throughout the year. But when taken to temperate regions, these potatoes will start tuber formation only as the September equinox approaches, and the delayed crop will then be killed by frost before it is mature. This explains why potatoes could not be grown in Europe until day-neutral (or photoperiod-insensitive) cultivars were found. Photosynthesis
All living organisms can be divided into three groups called producers, reducers, and consumers. Producers are the only organisms that can convert solar energy into the sugars and starches (carbohydrates) on which all life is based. This process is called photosynthesis and it converts solar energy, water, and carbon dioxide into carbohydrates, giving off oxygen as a waste product. It occurs mainly in green plants that contain chlorophyll, but it can also occur in more primitive organisms such as the cyano-bacteria. Photosynthesising plants are thus at the bottom of the food chain and all life depends on them. They are also responsible for maintaining the world's supply of oxygen.
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