Wages in Solow growth model with savings = 0
Let 
$$Q = F(K,L)$$
Assume
a) $F(K,L)$ exhibits consant returns to scale.  

We need this to aggregate from the individual firms to the total.

b) Price taking behavior  and

c) Profit maximizing behavior  

from the part of the firms.  

Then, throughout the dynamic process,
$$w = \frac {\partial F(K,L)}{\partial L} \equiv F_L$$

i.e. the wage is equal to the marginal product of labor. For clarity, write 

$$\frac {\partial F(K,L)}{\partial L} \equiv h(K,L)$$

$$\dot w = \frac {d}{dt}\frac {\partial F(K,L)}{\partial L} = \frac {d}{dt}h(K,L)= \frac {\partial h(K,L)}{\partial K}\dot K + \frac {\partial h(K,L)}{\partial L}\dot L$$

$$\implies \dot w = F_{KL}\dot K + F_{LL}\dot L$$

Assume  further

d) complementarity of inputs, $F_{KL}&gt;0$, and  

e) diminishing marginal productss (not in the temporal dimension but in the static dimension, due to diminishing rate of returns), $F_{LL}&lt;0, F_{KK}&lt;0$.  

Then, if 

$$\dot K &lt;0, \dot L\geq 0  \implies \dot w &lt;0$$

The same treatment wil give us

$$\dot r = F_{KK}\dot K + F_{KL}\dot L  &gt;0$$