Transport in plants

TRANSPORT  IN  PLANTS: Plants  lack both interstitial  fluid as well as a regular circulation  system. Even then they have to move ( transport) various  types of substances  not only to short distance  but also to every long distances. Substances  moves over short distances through diffusion  and active transport  supplemented by Cytoplasmic streaming. Long distance transport  occurs through vascular  systems, xylem and phloem. This transport of substances  over longer distances through the vascular  tissue  is called translocation. It occurs through mass flow. Translocation  operates either  due to positive hydrostatic  pressure gradient  as in phloem  or a negative  hydrostatic  pressure gradient as in xylem. The direction of translocation is essentially  unidirectional  in case of water ( from root to stem, leaves, flowers and fruits). It is multidirectional in case  of minerals and organic solutes. Organic compounds are synthesized in leaves. They are exported to all other parts in

Guttation Biology

 GUTTATION  The loss of water in the form of liquid droplets from the leaves and  other parts of an uninjured  plant is called guttation.  All plants do not show guttation . Common examples are found in Garden Nasturtium,  Oat and other cereals, Balsam, Tomato, and Cucurbits.   The guttated liquid is never pure water. It contains 0.6 _ 2.5 gm/ litre of solutes _ both organic and inorganic. Evaporation  of guttated liquid will leave the solutes on the surface of the leaf in term of a white crust ( another reason for the latter is excretion of salts in some halophytes). Guttation  usually  occurs  during periods of active growth when conditons favour more water absorption  and less transpiration. Such conditions are found in humid tropical areas,  rainy seasons and late spring in temperate areas. It takes place either at night or early in  the morning.  Dry soils, poorly aerated soils, heavily salted or mineral deficient soils and atmospheric conditions promoting transpiration inhibit th


 Transpiration, Types of Transpiration: &Stomatal Apparatus Transpiration:  The loss of water in the vapour form from the exposed parts of a plant is called transpiration. 98_99% of the water absorbed is lost in transpiration. Only 0.2% is used in photosynthesis while the remaining is retained in the plant during growth. Water loss from a leaf can be studied using cobalt chloride paper, which turns colours ( from blue to pink) on absorbing  water.  The Magnitude of Transpiration:  As far as the magnitude  of transpiration  is concerned, Mayer ( 1956) had reported that some of the herbaceous  plants, under favourable  conditions, transport the entire volume of water a plant has and it is replaced within a single day. This means that of all the water absorbed by plants, approximately 95 per cent is lost  by transpiration, and 5 per cent or loss is used in the plant. If it were not for the loss of water by transpiration, a  single  rain or irrigation would  have been provided the enou