Mezofita – group very various not only on specific structure, but also on various ecological shades caused by a different combination of factors in natural habitats. They are connected by transitions with other ecological types of plants in relation to water so between them to draw a clear boundary very difficult. So, types with raised vlagolyubiy, constantly crude or temporarily filled in sites preferring are distinguished from meadow mezofit (a foxtail meadow – Alopecurus pratensis, a bekmaniye ordinary – Beckmannia eruciformis).
MEZOFITY. This group includes the plants growing in average conditions of moistening. Here plants of meadows, a grass cover of the woods, deciduous tree and shrubby species from areas of moderately humid climate, and also the majority of cultural plants belong.
Kserofita with the most pronounced kseromorfny lines of a structure of leaves have a peculiar appearance, for what received the name of sklerofit. It is easy to present shape of a typical sklerofit on the example of a thistle – Carduus crispus and desert ice-holes, hobble, saxauls.
Plants with floating leaves use partially water, partially air environment. From them jugs from the sort Nuphar, rdesta, a nut water – Trapa natans take roots in water-lily soil from the sort Nymphaea.
The adverse water mode of plants in dry habitats is caused, first, by limited water inflow at its lack of the soil and, secondly, increase in a consumption of moisture at a transpiration at big dryness of air and high temperatures. Therefore, for overcoming of a lack of moisture different ways are possible: increase in its absorption and reduction of an expense, besides, ability to transfer big losses of water. All this is used by kserofita at adaptation to dryness, but at different plants in unequal degree in this connection some authors distinguish two main ways of overcoming of a kserofitama of a drought: opportunity to resist to a siccation of fabrics, or active regulation of water balance, and ability to take out a strong siccation.
Transpiration at succulents is extremely small. It is difficult to catch it for the short period and it is necessary to define a water consumption not for an hour, and in days or in a week. Water-retaining ability of fabrics of succulents is much higher, than at other plants of ecological groups, thanks to the contents in cages of hydrophilic substances. Therefore and without moisture access succulents spend a water stock very slowly and long keep viability even in a herbarium.
Reduction of a sheet surface during the hottest and dry periods of a vegetative season. For many bushes of the Central Asian, North African and other deserts, and also for some types of dry subtropics of the Mediterranean the seasonal deformizm of leaves is characteristic: in the early spring at even favorable water mode rather large leaves which in the summer, at approach of a heat and dryness, are replaced by small leaves of more kseromorfny structure with smaller intensity of a transpiration are formed.
The restrictions caused by features of the water mode of succulents create also other difficulties for life of these plants in arid conditions. The weak transpiration minimizes possibility of thermal control with what strong heating of massive elevated bodies of succulents is connected. Difficulties are created and for photosynthesis as in the afternoon of ustiyets are usually closed, and open at night, therefore, access of carbonic acid and light do not synchronize. Therefore at succulents the special way of photosynthesis at which as a carbonic acid source, breath products are partially used was developed. In other words, in extreme conditions of a plant partially use the principle of the closed system with a reutilization of waste of a metabolism.
Cells of fabrics of leaves at kserofit differ in the small sizes and very dense packing, that is small development of mezhkletnik thanks to what the internal evaporating leaf surface is strongly reduced. As kserofita usually live on the open, well lit habitats, many lines of kseromorfny structure of a leaf is at the same time and lines of light structure. So at many types leaves have the multirow palisadny parenchyma powerful sometimes which is often located from both parties.