Click not work proper in select menu

i have one select/option menu with label… problem is that when i add css at that time menu open on arrow click not on whole row click. and when i remove css .click on any place in whole row open menu. why it happened??
code that i used.
if i write like that …not clik in whole row only arrow click available.

    <ion-label class="text-center">Connection Detail</ion-label>
     <ion-item>
        <ion-label>Box Type</ion-label>
        <ion-select [formControl]="dthactivationForm.controls.boxControl" (ionChange)="detailSelected()">
        <ion-option *ngFor="let item of boxArray" value="{{item.id}}" >{{item.text}}</ion-option>
        </ion-select>
     </ion-item>

css file

    .text-center{
    	font-size: 110%;
    	text-align: center;
    	background-color: #a1c1da;
    }
    button
    {
      	margin-top: 10%;
    }

if i write below code than i able to click any where in row

    <ion-label>Connection Detail</ion-label>
     <ion-item>
        <ion-label>Box Type</ion-label>
        <ion-select [formControl]="dthactivationForm.controls.boxControl" (ionChange)="detailSelected()">
        <ion-option *ngFor="let item of boxArray" value="{{item.id}}" >{{item.text}}</ion-option>
        </ion-select>
     </ion-item>

nothing in css file

Can you put together a demo of this?