Question

How does cyclosis helps in hormone transport on plants

Answer 1

The green plant, like an army, has two all-consuming activities, without which it can not hope to prevail. The first of these is logistics. The second is command, communication, andcontrol (C3). Because the topic of this is essay cytoplasmic (protoplasmic) streaming in the context of symplastic transport, these two imperatives will be treated in the context of a cell whose contents are convecting.

Logistics is the art/science of getting the supplies needed to the unit (a cell) and distributing them appropriately. in the context of the cell. This means: (i) taking them up, either across the plasmalemma from the apoplast or from the protoplasm of a neighbouring cell by way of connecting plasmodesmata; and (ii) distributing them appropriately within the protoplasm. Our focus will be upon distribution.

C3 is the art/science of gathering reliable information and then transmitting unambiguous orders to appropriate effectuators. In the context of the cell, which participates in a far more decentralized command structure than an army, this means: (i) carrying out its programmed activities; (ii) sensing its surroundings and its internal state and transmitting appropriate information and/or commands; and (iii) receiving and effecting commands from elsewhere in the plant.

None of this is simple. and all of this must be done in a complex three-dimensional ultrastructural milieu which does not conform to the diffusion-dominated ‘watery bag’ model of yesteryear (Hochachka 1999). To paraphrase the elder Moltke, ‘in [physiology] with its enormous friction even the mediocre is quite an achievement’ (van Creveld 1985, p.13). Or to cite from Polybius (a soldier/historian of the 2nd century BC) a rather more direct parallel between war and biology: ‘nature makes a single trivial error sufficient to cause failure in a design, but correctness in every detail barely enough for success’ (van Creveld 1985, p. 264). That the plant fares very well indeed speaks volumes for the robustness and resilience of its strategies.

In the distribution of both supplies (logistics) and information (C3) the plant has many options, including:

1Convection. This form of mass transport is, in plant biology, typified by cytoplasmic streaming. If the supplies are metabolites, they will certainly be carried along by the motion of the cytoplasm. If the information is encoded in chemical messengers, it too will be carried along by the motion. However, the transport will be only along the streamlines of the flow: convection will never move metabolites or chemical messengers perpendicular to the flow. Convection is presently considered to be a result of endoplasmic ‘molecular motors’ running along actin microfilaments or possibly along microtubules (Reddy 2001). But it is an open question whether the convective flow (i) constitutes a major payoff arising from this motile activity; or (ii) is a byproduct of lesser utility which arises from drag on the entities towed by the moving motors. That is, how is the utility to the cell of motor motion to be apportioned between (a) stirring of the cytoplasm; and (b) siting of the towed entity at a new location; presumably a cost function exists and is reflected by plant evolution, even though we do not at present know how to formulate it.2Diffusion. This reflects the kinetic motion of the molecules comprising the cytosol. As a result of intermolecular collisions, a molecule in a particular compartment of the cytosol will execute a random walk and will, other influences being absent, tend in time to assume a uniform probability distribution within the compartment